Deep vein thrombosis: Difference between revisions

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'''Deep-vein thrombosis''' (also known as '''deep-venous thrombosis''' or '''DVT''' and colloquially as '''economy class syndrome''') is the formation of a [[blood clot]] ("thrombus") in a [[deep vein]].  It commonly affects the [[leg]] [[vein]]s, such as the [[femoral vein]] or the [[popliteal vein]] or the deep veins of the pelvis.  Occasionally the veins of the [[arm]] are affected (known as ''[[Paget-Schrötter disease]]'').  [[Thrombophlebitis]] is the more general class of pathologies of this kind.  
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'''Deep vein thrombosis''' (DVT), also known as deep-venous thrombosis, is the formation of a [[coagulation|blood clot]] ("thrombus") in a deep vein.  It commonly affects the [[leg]] [[vein]]s, such as the [[femoral vein]] or the [[popliteal vein]] or the deep veins of the pelvis.  Occasionally the veins of the [[arm]] are affected (known as ''[[Paget-Schrötter disease]]'').  [[Embolism and thrombosis]] is the more general class of pathologies of this kind.
 
Thrombi may develop first in the calf veins ([[calf vein thrombosis]]), "growing" in the direction of flow of the vein.  DVTs are distinguished as being above or below the trifucation of the [[popliteal vein]].  Very extensive DVTs can extend into the [[iliac vein]]s or the [[inferior vena cava]].  The risk of pulmonary embolism is higher in the presence of more extensive clots.
 
==Epidemiology==
DVTs occur in about 1 per 1000 persons per year. About 1-5% will die from the complications (i.e. [[pulmonary embolism]]). 
 
DVT is much less common in the pediatric population.  About 1 in 100,000 people under the age of 18 experiences deep vein thrombosis, possibly due to a child's high rate of heartbeats per minute, relatively active lifestyle when compared with adults, and fewer comorbodities (e.g. malignancy).
 
Medical inpatients at risk of DVT can be identified with [[clinical prediction rule]]s.<ref name="pmid21962315">{{cite journal| author=Woller SC, Stevens SM, Jones JP, Lloyd JF, Evans RS, Aston VT et al.| title=Derivation and validation of a simple model to identify venous thromboembolism risk in medical patients. | journal=Am J Med | year= 2011 | volume= 124 | issue= 10 | pages= 947-954.e2 | pmid=21962315 | doi=10.1016/j.amjmed.2011.06.004 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21962315  }} </ref><ref name="pmid15758007">{{cite journal| author=Kucher N, Koo S, Quiroz R, Cooper JM, Paterno MD, Soukonnikov B et al.| title=Electronic alerts to prevent venous thromboembolism among hospitalized patients. | journal=N Engl J Med | year= 2005 | volume= 352 | issue= 10 | pages= 969-77 | pmid=15758007 | doi=10.1056/NEJMoa041533 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=15758007  }} </ref>
 
{| class="wikitable"
|+ Predicting which medical inpatients will develop DVT.<ref name="pmid21962315"/><ref name="pmid15758007"/>
! &nbsp;!! heading
|-
| RAM<ref name="pmid21962315"/> || prior VTE<br/>order for bed rest<br/>PICC insertion<br/>cancer
|-
| Kucher  score<ref name="pmid15758007"/>||
Cancer 3 points<br/>
Prior VTE 3<br/>
Hypercoagulability 3<br/>
Major surgery 2<br/>
Bed rest 1<br/>
Age >70 years 1<br/>
Obesity ([[Body mass index|BMI]] >30) 1<br/>
Estrogens 1
|}
 
==Cause/etiology==
===Virchow's triad===
Many factors are involved in the formation of a thrombus (clot).  [[Virchow's triad]] is a group of 3 factors known to affect clot formation: rate of flow, the consistency (thickness) of the blood, and qualities of the vessel wall.  Among the risk factors are advanced age, obesity, infection, immobilization, female sex, use of [[oral contraceptive]]s, tobacco usage and air travel ("economy class syndrome", a combination of immobility and relative dehydration) are some of the better-known causes.<ref>{{cite journal | author = Tsai A, Cushman M, Rosamond W, Heckbert S, Polak J, Folsom A | title = Cardiovascular risk factors and venous thromboembolism incidence: the longitudinal investigation of thromboembolism etiology. | journal = Arch Intern Med | volume = 162 | issue = 10 | pages = 1182-9 | year = 2002 | id = PMID 12020191}}</ref>  [[Thrombophilia]] (tendency to develop thrombosis) often expresses itself with recurrent thromboses.
 
====Underlying malignancy====
DVT may be due to underlying malignancy, especially if the DVT is associated with older age, idiopathic DVT, bilateral thrombosis, or anemia.<ref name="pmid18021305">{{cite journal |author=Trujillo-Santos J, Prandoni P, Rivron-Guillot K, ''et al'' |title=Clinical outcome in patients with venous thromboembolism and hidden cancer: findings from the RIETE Registry |journal=J Thromb Haemost |volume=6 |issue=2 |pages=251–255 |year=2008 |pmid=18021305 |doi=10.1111/j.1538-7836.2007.02837.x |issn=}}</ref> These patients have a worse prognosis.
 
===Genetics===
A [[twin study]] found a genetic contribution to venous thromboembolism among men but not women.<ref name="pmid12859034">{{cite journal |author=Larsen TB, Sørensen HT, Skytthe A, Johnsen SP, Vaupel JW, Christensen K |title=Major genetic susceptibility for venous thromboembolism in men: a study of Danish twins |journal=Epidemiology |volume=14 |issue=3 |pages=328-32 |year=2003 |pmid=12859034 |doi= |url=http://meta.wkhealth.com/pt/pt-core/template-journal/lwwgateway/media/landingpage.htm?issn=1044-3983&volume=14&issue=3&spage=328 |issn=}}</ref> Among men, the concordance rates for mono- and dizygotic twin pairs were 0.22 and 0.08.
 
Various [[single-nucleotide polymorphism]]s (SNPs) have been associated with DVT.<ref> Bezemer, I. D., Bare, L. A., Doggen, C. J. M., Arellano, A. R., Tong, C., Rowland, C. M., et al. (2008). Gene variants associated with deep vein thrombosis, JAMA, 299(11), 1306-1314. {{doi|10.1001/jama.299.11.1306}}.</ref>


==Signs and symptoms==
==Signs and symptoms==
Line 22: Line 62:
[[Impedance plethysmography]]  and [[Doppler ultrasonography]] are non-invasive alternatives.
[[Impedance plethysmography]]  and [[Doppler ultrasonography]] are non-invasive alternatives.


===Probability scoring===
===Probability scoring for lower extremity DVT===
In [[2006]], Scarvelis and Wells overviewed a set of clinical criteria for DVT,<ref>{{cite journal | author = Scarvelis D, Wells P | title = Diagnosis and treatment of deep-vein thrombosis. | journal = CMAJ | volume = 175 | issue = 9 | pages = 1087-92 | year = 2006 | id = PMID 17060659. [http://www.cmaj.ca/cgi/content/full/175/9/1087 Free Full Text] }}</ref> on the heels of a widely adopted set of clinical criteria for pulmonary embolism.<ref>Neff MJ. ACEP releases clinical policy on evaluation and management of pulmonary embolism. ''American Family Physician''. 2003; '''68'''(4):759-?.  Available at: [http://www.aafp.org/afp/20030815/practice.html http://www.aafp.org/afp/20030815/practice.html]. Accessed on: December 8, 2006.</ref><ref>{{cite journal | author = Wells P, Anderson D, Rodger M, Ginsberg J, Kearon C, Gent M, Turpie A, Bormanis J, Weitz J, Chamberlain M, Bowie D, Barnes D, Hirsh J | title = Derivation of a simple clinical model to categorize patients probability of pulmonary embolism: increasing the models utility with the SimpliRED D-dimer. | journal = Thromb Haemost | volume = 83 | issue = 3 | pages = 416-20 | year = 2000 | id = PMID 10744147}}</ref>  
====Wells rule====
The best studied [[clinical prediction rule]] is the Wells rule; however, use of the Wells rule is complicated by the rule having been modified over time. For example, in a recent review, the version of the Wells rule used in the articles was not clear although studies were published over a range of years.<ref name="pmid24615063">{{cite journal| author=Geersing GJ, Zuithoff NP, Kearon C, Anderson DR, Ten Cate-Hoek AJ, Elf JL et al.| title=Exclusion of deep vein thrombosis using the Wells rule in clinically important subgroups: individual patient data meta-analysis. | journal=BMJ | year= 2014 | volume= 348 | issue= | pages= g1340 | pmid=24615063 | doi=10.1136/bmj.g1340 | pmc=PMC3948465 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=24615063  }} </ref> This has resulted in guidelines recommending use of outdated versions of the Wells rule.<ref name="pmid17371890">{{cite journal |author=Qaseem A, Snow V, Barry P, ''et al'' |title=Current diagnosis of venous thromboembolism in primary care: a clinical practice guideline from the American Academy of Family Physicians and the American College of Physicians |journal=Ann. Intern. Med. |volume=146 |issue=6 |pages=454–8 |year=2007 |pmid=17371890 |doi=}}</ref> The rule was introduced in 1995.<ref name="pmid7752753">{{cite journal |author=Wells PS, Hirsh J, Anderson DR, ''et al'' |title=Accuracy of clinical assessment of deep-vein thrombosis |journal=Lancet |volume=345 |issue=8961 |pages=1326–30 |year=1995 |pmid=7752753 |doi=}}</ref>


'''Wells score or criteria''':
{|align="right" cellpadding="10" style="background-color:#FFFFCC; width:50%; border: 1px solid #aaa; margin:20px; font-size: 92%;"
(Possible score -2 to 9)
|'''2003<ref name="pmid14507948">{{cite journal |author=Wells PS, Anderson DR, Rodger M, ''et al'' |title=Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis |journal=N. Engl. J. Med. |volume=349 |issue=13 |pages=1227–35 |year=2003 |pmid=14507948 |doi=10.1056/NEJMoa023153|url=http://content.nejm.org/cgi/content/full/349/13/1227}}</ref>-2006<ref name="pmid17060659"/> Wells 10 point rule''':
# Active cancer (treatment within last 6 months or palliative) -- 1 point
# Calf swelling >3cm compared to other calf (measured 10cm below tibial tuberosity) -- 1 point
# Collateral superficial veins (non-varicose) -- 1 point
# Pitting edema (confined to symptomatic leg) -- 1 point
# Swelling of entire leg - 1 point
# Localized pain along distribution of deep venous system -- 1 point
# Paralysis, paresis, or recent cast immobilization of lower extremities -- 1 point
# Recently bedridden > 3 days, or major surgery requiring regional or general anesthetic in past 12 weeks -- 1 point
# Previously documented DVT -- 1 point
# Alternative diagnosis at least as likely -- Subtract 2 points
'''Interpretation''':
: Score of 2 or higher - deep vein thrombosis is likely. Consider imaging the leg veins.
: Score of less than 2 - deep vein thrombosis is unlikely. Consider blood test such as [[d-dimer]] test to further rule out deep vein thrombosis.
|}


:1) Active cancer (treatment within last 6 months or palliative) -- 1 point
'''2003 Wells 10 point rule''':In 2003, Wells published a 10 point rule that adds a point for history of previous DVT (yellow box).<ref name="pmid14507948">{{cite journal |author=Wells PS, Anderson DR, Rodger M, ''et al'' |title=Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis |journal=N. Engl. J. Med. |volume=349 |issue=13 |pages=1227–35 |year=2003 |pmid=14507948 |doi=10.1056/NEJMoa023153|url=http://content.nejm.org/cgi/content/full/349/13/1227}}</ref> In 2006, Wells reviewed the available [[clinical prediction rule]]s for DVT and did not further modify the 2003 rule.<ref name="pmid17060659">{{cite journal |author=Scarvelis D, Wells PS |title=Diagnosis and treatment of deep-vein thrombosis |journal=CMAJ |volume=175 |issue=9 |pages=1087–92 |year=2006 |pmid=17060659 |doi=10.1503/cmaj.060366|url=http://www.cmaj.ca/cgi/content/full/175/9/1087}}</ref>


:2) Calf swelling >3cm compared to other calf (measured 10cm below tibial tuberosity) -- 1 point
Based on his 2003 study, Wells recommends that DVT is excluded only when the 10-point score is < 2 and the D-dimer is negative.<ref name="pmid17060659"/> Independent studies validate the Wells 10 point rule.<ref name="pmid23318311">{{cite journal| author=Linkins LA, Bates SM, Lang E, Kahn SR, Douketis JD, Julian J et al.| title=Selective d-Dimer Testing for Diagnosis of a First Suspected Episode of Deep Venous Thrombosis: A Randomized Trial. | journal=Ann Intern Med | year= 2013 | volume= 158 | issue= 2 | pages= 93-100 | pmid=23318311 | doi=10.7326/0003-4819-158-2-201301150-00003 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=23318311  }} </ref><ref name="pmid21242558">{{cite journal| author=van der Velde EF, Toll DB, Ten Cate-Hoek AJ, Oudega R, Stoffers HE, Bossuyt PM et al.| title=Comparing the diagnostic performance of 2 clinical decision rules to rule out deep vein thrombosis in primary care patients. | journal=Ann Fam Med | year= 2011 | volume= 9 | issue= 1 | pages= 31-6 | pmid=21242558 | doi=10.1370/afm.1198 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21242558  }} </ref><ref name="pmid24615063"/> However, the d-dimer assays vary; for rapid quantitative immunoturbidimetric assays, a cutoff of 1.0 <g/mL is used.<ref name="pmid23318311">{{cite journal| author=Linkins LA, Bates SM, Lang E, Kahn SR, Douketis JD, Julian J et al.| title=Selective d-Dimer Testing for Diagnosis of a First Suspected Episode of Deep Venous Thrombosis: A Randomized Trial. | journal=Ann Intern Med | year= 2013 | volume= 158 | issue= 2 | pages= 93-100 | pmid=23318311 | doi=10.7326/0003-4819-158-2-201301150-00003 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=23318311  }} </ref>


:3) Collateral superficial veins (non-varicose) -- 1 point
'''Earlier version: 1995 Original Wells 12 point rule''':<ref name="pmid7752753"/><br>
Major points
*Active cancer (treatment ongoing or within previous 6 months or palliative)
*Paralysis, paresis. or recent plaster irnmobilisation of the lower extremities
*Recently bedridden >3 days and/or major surgery within 4 weeks
*Localised tenderness along tl’e distribution of the deep venous system
*Thigh and calf swollen (should be measured)  
*Calf swelling 3cm >symptornless side (measured 10cm below tibial tuberosity
*Strong family history of (NT (2 first degree relatives with history of CVI)
Minor points
*History of recent trauma C 60 days) to the symptomatic leg
*Pitting oedema; symptomatic leg only
*Dilated superficial veins (non-varicose) in symptomatic leg only
*Hospitisation within previous 6 months
*Erythema


:4) Pitting edema (confined to symptomatic leg) -- 1 point
'''Earlier version: 1997 Wells 9 point rule''':<ref name="pmid9428249">{{cite journal |author=Wells PS, Anderson DR, Bormanis J, ''et al'' |title=Value of assessment of pretest probability of deep-vein thrombosis in clinical management |journal=Lancet |volume=350 |issue=9094 |pages=1795–8 |year=1997 |pmid=9428249 |doi=10.1016/S0140-6736(97)08140-3  }}</ref>


:5) Swelling of entire leg - 1 point
# Active cancer (treatment ongoing or within previous 6 months or palliative) - 1 point
# Paralysis, paresis, or recent plaster immobilisation of the lower extremities - 1 point
# Recently bedridden for more than 3 days or major surgery, within 4 weeks - 1 point
# Localised tenderness along the distribution of the deep venous system - 1 point
# Entire leg swollen - 1 point
# Calf swelling by more than 3 cm when compared with the asymptomatic leg (measured 10 cm below tibial tuberosity) - 1 point
# Pitting oedema (greater in the symptomatic leg) - 1 point
# Collateral superficial veins (non-varicose) - 1 point
# Alternative diagnosis as likely or greater than that of deep-vein thrombosis - subtract 2 points
:Interpretation:  low (score  0), medium (score of 1 or 2), or high (score  3)


:6) Localized pain along distribution of deep venous system -- 1 point
In 2005 a large study found that the 1997 Wells score failed to adequately exclude DVT in primary care patients.<ref name="pmid16027451">{{cite journal |author=Oudega R, Hoes AW, Moons KG |title=The Wells rule does not adequately rule out deep venous thrombosis in primary care patients |journal=Ann. Intern. Med. |volume=143 |issue=2 |pages=100–7 |year=2005 |pmid=16027451 |doi=|url=http://www.annals.org/cgi/content/full/143/2/100}}</ref> Unfortunately, the 2005 study was completed in March, 2003, 6 months prior to publication of the 2003 revision by Wells to his rule in which he added a 10th variable.


:7) Paralysis, paresis, or recent cast immobilization of lower extremities -- 1 point
====AMUSE Primary Care Rule====
Because of concerns about the failed study in 2005 of the older, 9-point 1997 Wells rule (not that the current Wells rule has 10 points)<ref name="pmid16027451"/>, the Amsterdam Maastricht Utrecht Study on thromboEmbolism (AMUSE) Investigators developed a rule with 7 clinical variable plus the D-dimer.<ref> Toll, DB et al. 2008. “A new diagnostic rule for deep vein thrombosis: safety and efficiency in clinically relevant subgroups.” Fam. Pract. 2008.  http://fampra.oxfordjournals.org/cgi/content/full/cmm075v1</ref><ref name="pmid19221374">{{cite journal |author=Büller HR, Ten Cate-Hoek AJ, Hoes AW, ''et al'' |title=Safely ruling out deep venous thrombosis in primary care |journal=Ann. Intern. Med. |volume=150 |issue=4 |pages=229–35 |year=2009 |month=February |pmid=19221374 |doi= |url=http://www.annals.org/cgi/pmidlookup?view=long&pmid=19221374 |issn=}}</ref>  Patients with a score of 3 or less are considered normal; patients with a score of 4 should receive [[ultrasonography]].
* Use of hormonal [[contraceptive]]s
* Active cancer in past 6 mo
* Surgery in previous month
* Absence of leg trauma
* Distention of collateral leg veins
* Difference in calf circumference ≥ 3 cm (2 points)
* Abnormal [[d-dimer]] assay (6 points)


:8) Recently bedridden > 3 days, or major surgery requiring regional or general anesthetic in past 12 weeks -- 1 point
Patients with score ≥ 4 should receive [[ultrasonography]] of the leg.


:9) Previously documented DVT -- 1 point
The AMUSE investigators report that their rule and the Wells 10 variable rule perform similarly.<ref name="pmid21242558">{{cite journal| author=van der Velde EF, Toll DB, Ten Cate-Hoek AJ, Oudega R, Stoffers HE, Bossuyt PM et al.| title=Comparing the diagnostic performance of 2 clinical decision rules to rule out deep vein thrombosis in primary care patients. | journal=Ann Fam Med | year= 2011 | volume= 9 | issue= 1 | pages= 31-6 | pmid=21242558 | doi=10.1370/afm.1198 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21242558  }} </ref>  This rule has not been externally validated by independent research groups.


:10) Alternative diagnosis at least as likely -- Subtract 2 points
===Probability scoring for upper extremity DVT===
The Constans Clinical Decision Score may help. Its components are:<ref name="pmid24687068">{{cite journal| author=Kleinjan A, Di Nisio M, Beyer-Westendorf J, Camporese G, Cosmi B, Ghirarduzzi A et al.| title=Safety and Feasibility of a Diagnostic Algorithm Combining Clinical Probability, d-Dimer Testing, and Ultrasonography for Suspected Upper Extremity Deep Venous Thrombosis: A Prospective Management Study. | journal=Ann Intern Med | year= 2014 | volume= 160 | issue= 7 | pages= 451-7 | pmid=24687068 | doi=10.7326/M13-2056 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=24687068  }} </ref>
* Venous material present (Centeral venous catheter or pacemaker thread) (1 point)
* Localized pain (1 point)
* Unilateral edema (1 point)
* Other diagnosis at least as plausible (-1 point)


'''Interpretation''':
A score of 1 or less, along with negative d-dimer, excluded DVT. Thus, the d-dimer should be checked on every patient suspected of upper extremity DVT.
: Score of 2 or higher - deep vein thrombosis is likely. Consider imaging the leg veins.
: Score of less than 2 - deep vein thrombosis is unlikely. Consider blood test such as [[d-dimer]] test to further rule out deep vein thrombosis.


===Imaging the leg veins===
===Imaging the leg veins===
Compression [[medical ultrasonography|ultrasound]] scanning of the leg veins, combined with duplex measurements (to determine blood flow), can reveal a [[blood clot]] and its extent (i.e. whether it is below or above the [[knee]]).
====Ultrasonography====
Compression B-mode [[ultrasonography]]<ref name="pmid2643771">{{cite journal| author=Lensing AW, Prandoni P, Brandjes D, Huisman PM, Vigo M, Tomasella G et al.| title=Detection of deep-vein thrombosis by real-time B-mode ultrasonography. | journal=N Engl J Med | year= 1989 | volume= 320 | issue= 6 | pages= 342-5 | pmid=2643771
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=2643771 }} <!--Formatted by http://sumsearch.uthscsa.edu/cite/--></ref> scanning of the leg veins, combined with [[Duplex Doppler ultrasonography]]<ref name="pmid2667418">{{cite journal| author=White RH, McGahan JP, Daschbach MM, Hartling RP| title=Diagnosis of deep-vein thrombosis using duplex ultrasound. | journal=Ann Intern Med | year= 1989 | volume= 111 | issue= 4 | pages= 297-304 | pmid=2667418
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=2667418 }} <!--Formatted by http://sumsearch.uthscsa.edu/cite/--></ref> (to determine blood flow), can reveal a [[thrombus]].
 
Distinguishing acute versus chronic thrombosis with [[Duplex Doppler ultrasonography]] has been examined in one study of 103 examination in 101 patients:<ref name="pmid8058929">{{cite journal| author=Lewis BD, James EM, Welch TJ, Joyce JW, Hallett JW, Weaver AL| title=Diagnosis of acute deep venous thrombosis of the lower extremities: prospective evaluation of color Doppler flow imaging versus venography. | journal=Radiology | year= 1994 | volume= 192 | issue= 3 | pages= 651-5 | pmid=8058929
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=8058929 }} <!--Formatted by http://sumsearch.uthscsa.edu/cite/--></ref>
* Acute DVT in 31 examinations. [[Duplex Doppler ultrasonography]]
* Chronic DVT in 10 patients. [[Duplex Doppler ultrasonography]] identified 6 of the 10. Two of the missed cases were in the calf.
* Combined acute and chronic DVT in 2 patients. [[Duplex Doppler ultrasonography]] identified the acute changes in both patients, but did not identify the chronic changes.
 
In this study "no results were false-positive for acute DVT due to the changes of chronic DVT."
 
=====Whole leg ultrasonography=====
 
{| class="wikitable" align="right"
|+ Risk outcomes following a single negative whole-leg compression [[ultrasonography]] according to a [[systematic review]].<ref name="pmid20124539">{{cite journal| author=Johnson SA, Stevens SM, Woller SC, Lake E, Donadini M, Cheng J et al.| title=Risk of deep vein thrombosis following a single negative whole-leg compression ultrasound: a systematic review and meta-analysis. | journal=JAMA | year= 2010 | volume= 303 | issue= 5 | pages= 438-45 | pmid=20124539
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=clinical.uthscsa.edu/cite&email=badgett@uthscdsa.edu&retmode=ref&cmd=prlinks&id=20124539 | doi=10.1001/jama.2010.43 }} <!--Formatted by http://sumsearch.uthscsa.edu/cite/--></ref>
! Wells score !! Death (%) from [[embolism and thrombosis]] ([[Confidence interval|95% CI]])
|-
| All patients|| 0.7%
|-
| Low risk|| 0.3% (0 to 0.7%)
|-
| Intermediate risk|| 0.8% (0 to 1.8%)
|-
| High risk || 2.5% (0 to 7.1%)
|}
 
Either whole leg [[Doppler ultrasonography]] or serial 2-point [[ultrasonography]] plus [[D-dimer]] are equivalent strategies according to a [[randomized controlled trial]]<ref name="pmid18840838">{{cite journal |author=Bernardi E, Camporese G, Büller HR, ''et al'' |title=Serial 2-point ultrasonography plus D-dimer vs whole-leg color-coded Doppler ultrasonography for diagnosing suspected symptomatic deep vein thrombosis: a randomized controlled trial |journal=JAMA : the journal of the American Medical Association |volume=300 |issue=14 |pages=1653–9 |year=2008 |month=October |pmid=18840838 |doi=10.1001/jama.300.14.1653 |url=http://jama.ama-assn.org/cgi/pmidlookup?view=long&pmid=18840838 |issn=}}</ref> that was included in the [[meta-analysis]].
 
An uncontrolled [[cohort study]] found that [[anticoagulation]] can be safely withheld in patients with normal whole leg [[Doppler ultrasonography]].<ref name="pmid15197015">{{cite journal| author=Stevens SM, Elliott CG, Chan KJ, Egger MJ, Ahmed KM| title=Withholding anticoagulation after a negative result on duplex ultrasonography for suspected symptomatic deep venous thrombosis. | journal=Ann Intern Med | year= 2004 | volume= 140 | issue= 12 | pages= 985-91 | pmid=15197015
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=15197015 }} <!--Formatted by http://sumsearch.uthscsa.edu/cite/--></ref>
 
====Venography====
Venography can determine acute versus chronic thrombosis:<ref name="pmid8058929">{{cite journal| author=Lewis BD, James EM, Welch TJ, Joyce JW, Hallett JW, Weaver AL| title=Diagnosis of acute deep venous thrombosis of the lower extremities: prospective evaluation of color Doppler flow imaging versus venography. | journal=Radiology | year= 1994 | volume= 192 | issue= 3 | pages= 651-5 | pmid=8058929
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=8058929 }} <!--Formatted by http://sumsearch.uthscsa.edu/cite/--></ref>
* Acute thrombosis is suggested by any of:
** "constant filling defect or thrombus was identified"
** "persistent nonfilling of a venous segment despite adequate technique"
** " abrupt termination of the opaque column of contrast material in a venous segment"
* Chronic thrombosis is suggested by any of:
** "irregular walls suggestive of retracted adherent thrombus"
** "a lumen smaller than expected"
** "numerous well-developed adjacent collateral veins"
** "Valvular incompetence in the deep veins was considered further evidence of chronic DVT but was not required for the diagnosis."


===Blood tests===
===Blood tests===
In a low-probability situation, current practice is to commence investigations by testing for [[D-dimer]] levels. This cross-linked [[fibrin degradation product]] is an indication that [[thrombosis]] is occurring, and that the [[blood clot]] is being dissolved by [[plasmin]].  A low D dimer level should prompt other possible diagnoses (such as a ruptured [[Baker's cyst]], if this has not been considered as part of the history).
In a low-probability situation, current practice is to commence investigations by testing for [[D-dimer]] levels. A low D dimer level should prompt other possible diagnoses (such as a ruptured [[Baker's cyst]], if this has not been considered as part of the history).


* [[D-dimer]] levels. This cross-linked [[fibrin degradation product]] is an indication that [[thrombosis]] is occurring, and that the [[blood clot]] is being dissolved by [[plasmin]]. Interpretation may be increased by using age adjusted levels:<ref name="pmid24643601">{{cite journal| author=Righini M, Van Es J, Den Exter PL, Roy PM, Verschuren F, Ghuysen A et al.| title=Age-adjusted D-dimer cutoff levels to rule out pulmonary embolism: the ADJUST-PE study. | journal=JAMA | year= 2014 | volume= 311 | issue= 11 | pages= 1117-24 | pmid=24643601 | doi=10.1001/jama.2014.2135 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=24643601  }} </ref>
**  "In patients younger than 50 years, PE was excluded in those with a D-dimer value lower than 500 µg/L.{"
** "In patients 50 years or older, the D-dimer test result was considered negative in those with a D-dimer value lower than their age multiplied by 10."
Other blood tests usually performed at this point are:
Other blood tests usually performed at this point are:
* [[complete blood count]]
* [[complete blood count]]
* Primary [[coagulation]] studies: [[prothrombin time|PT]], [[APTT]], [[Fibrinogen]]
* Primary [[coagulation]] studies: [[prothrombin time|PT]], [[APTT]], [[Fibrinogen]], [[International Normalized Ratio[[
* [[liver enzyme]]s
* [[liver function test]]s
* [[renal function]] and [[electrolyte]]s
* [[renal function]] and [[electrolyte]]s
===Differential diagnosis===
Rupture of the tendon of the plantaris muscle<ref name=WPpm>Wikipedia has an [[Wikipedia:Plantaris muscle|article about the plantaris muscle.]]</ref>
may mimic [[deep venous thrombosis]].<ref>{{Cite journal
| doi = 10.1016/j.jemermed.2007.12.027
| last =  Lopez
| first = Gregory J
| coauthors = Hoffman RS, Davenport M
| title = Plantaris rupture: A mimic of deep venous thrombosis
| journal = Journal of Emergency Medicine
| accessdate = 2009-01-16
| url = http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T8B-4VCNF04-1&_user=10&_coverDate=01%2F15%2F2009&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=39c5d35cd5129be481316511a39b3d1d
}}</ref>
==Prophylaxis (Prevention)==
===General Medical Inpatients===
[[Clinical practice guideline]]s state:
* [[American College of Physicians]] (ACP) in 2011:<ref>{{Cite journal | doi = 10.1059/0003-4819-155-9-201111010-00011
| volume = 155 | issue = 9 | pages = 625 -632 | last = Qaseem | first = Amir | coauthors = Roger Chou, Linda L. Humphrey, Melissa Starkey, Paul Shekelle | title = Venous Thromboembolism Prophylaxis in Hospitalized Patients: A Clinical Practice Guideline From the American College of Physicians | journal = Annals of Internal Medicine | accessdate = 2011-11-01 | date = 2011-11-01 | url = http://www.annals.org/content/155/9/625.abstract }}</ref><ref>{{Cite journal | doi = 10.1059/0003-4819-155-9-201111010-00008
| volume = 155 | issue = 9 | pages = 602 -615 | last = Lederle | first = Frank A. | coauthors = Dylan Zylla, Roderick MacDonald, Timothy J. Wilt | title = Venous Thromboembolism Prophylaxis in Hospitalized Medical Patients and Those With Stroke: A Background Review for an American College of Physicians Clinical Practice Guideline | journal = Annals of Internal Medicine | accessdate = 2011-11-01 | date = 2011-11-01 | url = http://www.annals.org/content/155/9/602.abstract }}</ref>
**"ACP recommends assessment of the risk for thromboembolism and bleeding in medical (including stroke) patients prior to initiation of prophylaxis of venous thromboembolism (Grade: strong recommendation, moderate-quality evidence)."
**"ACP recommends pharmacologic prophylaxis with heparin or a related drug for venous thromboembolism in medical (including stroke) patients unless the assessed risk for bleeding outweighs the likely benefits (Grade: strong recommendation, moderate-quality evidence)."
**"ACP recommends against the use of mechanical prophylaxis with graduated compression stockings for prevention of venous thromboembolism (Grade: strong recommendation, moderate-quality evidence)."
**"ACP does not support the application of performance measures in medical (including stroke) patients that promotes universal venous thromboembolism prophylaxis regardless of risk."
* [[American College of Chest Physicians]] (ACCP) in 2011:<ref name="pmid22315261">{{cite journal| author=Kahn SR, Lim W, Dunn AS, Cushman M, Dentali F, Akl EA et al.| title=Prevention of VTE in nonsurgical patients: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. | journal=Chest | year= 2012 | volume= 141 | issue= 2 Suppl | pages= e195S-226S | pmid=22315261 | doi=10.1378/chest.11-2296 | pmc=PMC3278052 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22315261  }} </ref>
* "For acutely ill hospitalized medical patients at increased risk of thrombosis, we recommend anticoagulant thromboprophylaxis with low-molecular-weight heparin (LMWH), low-dose unfractionated heparin (LDUH) bid, LDUH tid, or fondaparinux (Grade 1B) and suggest against extending the duration of thromboprophylaxis beyond the period of patient immobilization or acute hospital stay (Grade 2B).
* "For acutely ill hospitalized medical patients at low risk of thrombosis, we recommend against the use of pharmacologic prophylaxis or mechanical prophylaxis (Grade 1B)."
* "For acutely ill hospitalized medical patients at increased risk of thrombosis who are bleeding or are at high risk for major bleeding, we suggest mechanical thromboprophylaxis with graduated compression stockings (GCS) (Grade 2C) or intermittent pneumatic compression (IPC) (Grade 2C)."
* "For critically ill patients, we suggest using LMWH or LDUH thromboprophylaxis (Grade 2C). For critically ill patients who are bleeding or are at high risk for major bleeding, we suggest mechanical thromboprophylaxis with GCS and/or IPC at least until the bleeding risk decreases (Grade 2C)."
* "In outpatients with cancer who have no additional risk factors for VTE we suggest against routine prophylaxis with LMWH or LDUH (Grade 2B) and recommend against the prophylactic use of vitamin K antagonists (Grade 1B)."
Extending anticoagulation for an addition 28 days may benefit patients who are "women, patients older than 75 years, and those with level 1 mobility. Level I mobility is being bed rest or sedentary without bathroom privileges."<ref name="pmid20621900">{{cite journal| author=Hull RD, Schellong SM, Tapson VF, Monreal M, Samama MM, Nicol P et al.| title=Extended-duration venous thromboembolism prophylaxis in acutely ill medical patients with recently reduced mobility: a randomized trial. | journal=Ann Intern Med | year= 2010 | volume= 153 | issue= 1 | pages= 8-18 | pmid=20621900 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20621900 | doi=10.1059/0003-4819-153-1-201007060-00004 }} </ref>
Compression devices that are mobile may be effective.<ref name="pmid20194309">{{cite journal| author=Colwell CW, Froimson MI, Mont MA, Ritter MA, Trousdale RT, Buehler KC et al.| title=Thrombosis prevention after total hip arthroplasty: a prospective, randomized trial comparing a mobile compression device with low-molecular-weight heparin. | journal=J Bone Joint Surg Am | year= 2010 | volume= 92 | issue= 3 | pages= 527-35 | pmid=20194309
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=clinical.uthscsa.edu/cite&retmode=ref&cmd=prlinks&id=20194309 | doi=10.2106/JBJS.I.00047 }} </ref>
[[Rosuvastatin]], a [[hydroxymethylglutaryl-coenzyme A reductase inhibitor]] (statin), may reduce [[embolism and thrombosis]] according to the Jupiter [[randomized controlled trial]].<ref name="pmid19329822">{{cite journal |author=Glynn RJ, Danielson E, Fonseca FA, ''et al'' |title=A Randomized Trial of Rosuvastatin in the Prevention of Venous Thromboembolism |journal=N. Engl. J. Med. |volume= |issue= |pages= |year=2009 |month=March |pmid=19329822 |doi=10.1056/NEJMoa0900241 |url=http://content.nejm.org/cgi/pmidlookup?view=short&pmid=19329822&promo=ONFLNS19 |issn=}}</ref>
Studies on implementing guidelines are available.<ref name="pmid15758007"/><ref name="pmid21948203">{{cite journal| author=Khanna R, Vittinghoff E, Maselli J, Auerbach A| title=Unintended consequences of a standard admission order set on venous thromboembolism prophylaxis and patient outcomes. | journal=J Gen Intern Med | year= 2012 | volume= 27 | issue= 3 | pages= 318-24 | pmid=21948203 | doi=10.1007/s11606-011-1871-x | pmc=PMC3286563 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21948203  }} </ref>
===Oncology patients===
According to a [[clinical practice guideline]] by the American Society of Clinical Oncology, "all hospitalized cancer patients should be considered for VTE prophylaxis with anticoagulants in the absence of bleeding or other contraindications."<ref name="pmid17968019">{{cite journal |author=Lyman GH, Khorana AA, Falanga A, ''et al'' |title=American Society of Clinical Oncology Guideline: Recommendations for Venous Thromboembolism Prophylaxis and Treatment in Patients With Cancer |journal= |volume= |issue= |pages= |year=2007 |pmid=17968019 |doi=10.1200/JCO.2007.14.1283 |issn=}}</ref>
For oncology patients who have had a thrombus, consider lifelong prophylaxis with [[enoxaparin]] 1.5 mg/kg per day.<ref name="pmid18425959">{{cite journal |author=Akl EA, Barba M, Rohilla S, ''et al'' |title=Anticoagulation for the long term treatment of venous thromboembolism in patients with cancer |journal=Cochrane Database Syst Rev |volume= |issue=2 |pages=CD006650 |year=2008 |pmid=18425959 |doi=10.1002/14651858.CD006650.pub2 |url=http://dx.doi.org/10.1002/14651858.CD006650.pub2 |issn=}}</ref>
===Surgery Patients===
The risk of DVT after surgery may persist up to 12 weeks.<ref name="pmid19959589">{{cite journal| author=Sweetland S, Green J, Liu B, Berrington de González A, Canonico M, Reeves G et al.| title=Duration and magnitude of the postoperative risk of venous thromboembolism in middle aged women: prospective cohort study. | journal=BMJ | year= 2009 | volume= 339 | issue=  | pages= b4583 | pmid=19959589
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=clinical.uthscsa.edu/cite&email=badgett@uthscdsa.edu&retmode=ref&cmd=prlinks&id=19959589 | doi=10.1136/bmj.b4583 }} <!--Formatted by http://sumsearch.uthscsa.edu/cite/--></ref>
====Hip or knee surgery====
[[Clinical practice guideline]]s by the [[American College of Chest Physicians]]<ref name="pmid22315265">{{cite journal| author=Falck-Ytter Y, Francis CW, Johanson NA, Curley C, Dahl OE, Schulman S et al.| title=Prevention of VTE in orthopedic surgery patients: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. | journal=Chest | year= 2012 | volume= 141 | issue= 2 Suppl | pages= e278S-325S | pmid=22315265 | doi=10.1378/chest.11-2404 | pmc=PMC3278063 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22315265  }} </ref> and the [[American Academy of Orthopaedic Surgeons]]<ref>(2007) [http://www.aaos.org/research/guidelines/PE_guideline.pdf American Academy of Orthopaedic Surgeons Clinical Guideline on Prevention of Pulmonary Embolism in Patients Undergoing Total Hip or Knee Arthroplasty] [http://www.guideline.gov/summary/summary.aspx?ss=15&doc_id=10850 Summary at the National Guidelines Clearinghouse]</ref> address prevention. Unfortunately, these guidelines have substantial conflict.<ref name="pmid19201714">{{cite journal| author=Eikelboom JW, Karthikeyan G, Fagel N, Hirsh J| title=American Association of Orthopedic Surgeons and American College of Chest Physicians guidelines for venous thromboembolism prevention in hip and knee arthroplasty differ: what are the implications for clinicians and patients? | journal=Chest | year= 2009 | volume= 135 | issue= 2 | pages= 513-20 | pmid=19201714 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=19201714 | doi=10.1378/chest.08-2655 }}</ref>
Low molecular weight heparins may provide better [[anticoagulation]] for prophylaxis of deep venous thrombosis among orthopedic patients than direct thrombin inhibitors because the latter may increase complications.<ref name="pmid20393944">{{cite journal| author=Salazar CA, Malaga G, Malasquez G| title=Direct thrombin inhibitors versus vitamin K antagonists or low molecular weight heparins for prevention of venous thromboembolism following total hip or knee replacement. | journal=Cochrane Database Syst Rev | year= 2010 | volume= 4 | issue=  | pages= CD005981 | pmid=20393944
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=clinical.uthscsa.edu/cite&retmode=ref&cmd=prlinks&id=20393944 | doi=10.1002/14651858.CD005981.pub2 }} </ref> However, if [[anticoagulation]] is started before surgery, direct thrombin inhibitors may be more effective.
Extending anticoagulation (25-35 days) with [[low molecular weight heparin]], such as [[enoxaparin]] 30 to 40 mg subcutaneously once daily can reduce symptomatic DVT in one of every 45 patients treated and can reduce any (symptomatic or assymptomatic) DVT in one of every 8 patients treated.<ref name="pmid11712876">{{cite journal |author=Hull RD, Pineo GF, Stein PD, ''et al'' |title=Extended out-of-hospital low-molecular-weight heparin prophylaxis against deep venous thrombosis in patients after elective hip arthroplasty: a systematic review |journal=Annals of internal medicine |volume=135 |issue=10 |pages=858–69 |year=2001 |month=November |pmid=11712876 |doi= |url=http://www.annals.org/cgi/content/full/135/10/858 |issn=}}</ref> As these studies were short term, it is likely that some patients with asymptomatic DVT progress to chronic [[venous insufficiency]].
Even knee arthroscopic meniscectomy may benefit from low molecular weight heparin.<ref name="pmid18626046">{{cite journal| author=Camporese G, Bernardi E, Prandoni P, Noventa F, Verlato F, Simioni P et al.| title=Low-molecular-weight heparin versus compression stockings for thromboprophylaxis after knee arthroscopy: a randomized trial. | journal=Ann Intern Med | year= 2008 | volume= 149 | issue= 2 | pages= 73-82 | pmid=18626046
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=18626046 }}  [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=19071876 Review in: ACP J Club. 2008 Dec 16;149(6):10] <!--Formatted by http://sumsearch.uthscsa.edu/cite/--></ref>
;Factor Xa inhibitors
* [[Fondaparinux]] for one week can prevent [[embolism and thrombosis]] during [[perioperative care]] according to [[randomized controlled trial]]s of hip fracture surgery<ref name="pmid11794148">{{cite journal |author=Eriksson BI, Bauer KA, Lassen MR, Turpie AG |title=Fondaparinux compared with enoxaparin for the prevention of venous thromboembolism after hip-fracture surgery |journal=The New England journal of medicine |volume=345 |issue=18 |pages=1298–304 |year=2001 |month=November |pmid=11794148 |doi= |url=http://content.nejm.org/cgi/pmidlookup?view=short&pmid=11794148&promo=ONFLNS19 |issn=}}</ref>.
* [[Rivaroxaban]] can prevent [[embolism and thrombosis]] during [[perioperative care]] according to [[randomized controlled trial]]s of two weeks of therapy after knee arthoplasty<ref name="pmid18579812">{{cite journal |author=Lassen MR, Ageno W, Borris LC, ''et al'' |title=Rivaroxaban versus enoxaparin for thromboprophylaxis after total knee arthroplasty |journal=The New England journal of medicine |volume=358 |issue=26 |pages=2776–86 |year=2008 |month=June |pmid=18579812 |doi=10.1056/NEJMoa076016 |url=http://content.nejm.org/cgi/content/full/358/26/2776 |issn=}}</ref> or 5 weeks of therapy after hip arthroplasty ([[absolute risk reduction]] 1.7%).<ref name="pmid18579811">{{cite journal |author=Eriksson BI, Borris LC, Friedman RJ, ''et al'' |title=Rivaroxaban versus enoxaparin for thromboprophylaxis after hip arthroplasty |journal=The New England journal of medicine |volume=358 |issue=26 |pages=2765–75 |year=2008 |month=June |pmid=18579811 |doi=10.1056/NEJMoa0800374 |url=http://content.nejm.org/cgi/pmidlookup?view=short&pmid=18579811&promo=ONFLNS19 |issn=}}</ref><ref name="pmid18582928">{{cite journal |author=Kakkar AK, Brenner B, Dahl OE, ''et al'' |title=Extended duration rivaroxaban versus short-term enoxaparin for the prevention of venous thromboembolism after total hip arthroplasty: a double-blind, randomised controlled trial |journal=Lancet |volume=372 |issue=9632 |pages=31–9 |year=2008 |month=July |pmid=18582928 |doi=10.1016/S0140-6736(08)60880-6 |url=http://linkinghub.elsevier.com/retrieve/pii/S0140-6736(08)60880-6 |issn=}} (this trial compared rivaroxaban to short-term enoxaparin</ref>
====Spinal surgery====
[[Clinical practice guideline]]s by the [[American College of Chest Physicians]] address this topic.<ref name="pmid22315263">{{cite journal| author=Gould MK, Garcia DA, Wren SM, Karanicolas PJ, Arcelus JI, Heit JA et al.| title=Prevention of VTE in nonorthopedic surgical patients: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. | journal=Chest | year= 2012 | volume= 141 | issue= 2 Suppl | pages= e227S-77S | pmid=22315263 | doi=10.1378/chest.11-2297 | pmc=PMC3278061 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22315263  }} </ref>
===Travelers===
Travel may<ref name="pmid19581633">{{cite journal| author=Chandra D, Parisini E, Mozaffarian D| title=Meta-analysis: travel and risk for venous thromboembolism. | journal=Ann Intern Med | year= 2009 | volume= 151 | issue= 3 | pages= 180-90 | pmid=19581633
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=19581633 }} <!--Formatted by http://sumsearch.uthscsa.edu/cite/--></ref> or may not<ref name="pmid19135280">{{cite journal| author=Beam DM, Courtney DM, Kabrhel C, Moore CL, Richman PB, Kline JA| title=Risk of thromboembolism varies, depending on category of immobility in outpatients. | journal=Ann Emerg Med | year= 2009 | volume= 54 | issue= 2 | pages= 147-52 | pmid=19135280
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=19135280 | doi=10.1016/j.annemergmed.2008.10.033 }} <!--Formatted by http://sumsearch.uthscsa.edu/cite/--></ref> lead to DVT according to meta-analyses.
Trials suggests that wearing compression socks while traveling also reduces the incidence of thrombosis in people on long haul flights. A randomized study in 2001 compared two sets of long haul airline passengers, one set wore travel compression hosiery the others did not. The passengers were all scanned and blood tested to check for the incidence of DVT. The results showed that asymptomatic DVT occurred in 10% of the passengers who did not wear compression socks. The group wearing compression had no DVTs. The authors concluded that wearing elastic compression hosiery reduces the incidence of DVT in long haul airline passengers.<ref name="pmid11377600">{{cite journal| author=Scurr JH, Machin SJ, Bailey-King S, Mackie IJ, McDonald S, Smith PD| title=Frequency and prevention of symptomless deep-vein thrombosis in long-haul flights: a randomised trial. | journal=Lancet | year= 2001 | volume= 357 | issue= 9267 | pages= 1485-9 | pmid=11377600
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=11377600 | doi=10.1016/S0140-6736(00)04645-6 }} <!--Formatted by http://sumsearch.uthscsa.edu/cite/--></ref>.


==Therapy==
==Therapy==
* [[Thrombolysis]] is generally reserved for extensive clot, e.g. an iliofemoral thrombosis.  Although a [[meta-analysis]] of [[randomized controlled trials]] by the [[Cochrane Collaboration]] shows improved outcomes with [[thrombolysis]],<ref name="pmid15495034">{{cite journal |author=Watson L, Armon M |title=Thrombolysis for acute deep vein thrombosis |journal=Cochrane Database Syst Rev |volume= |issue= |pages=CD002783 |year= |id=PMID 15495034}}</ref> there may be an increase in serious bleeding complications.
Treatment options have been reviewed.<ref name="pmid15254285">{{cite journal |author=Bates SM, Ginsberg JS |title=Clinical practice. Treatment of deep-vein thrombosis |journal=N. Engl. J. Med. |volume=351 |issue=3 |pages=268–77 |year=2004 |month=July |pmid=15254285 |doi=10.1056/NEJMcp031676 |url=http://content.nejm.org/cgi/pmidlookup?view=short&pmid=15254285&promo=ONFLNS19 |issn=}}</ref>
* [[Thrombolysis]] is generally reserved for extensive clot, e.g. an iliofemoral thrombosis.  Although a [[meta-analysis]] of [[randomized controlled trials]] by the [[Cochrane Collaboration]] shows improved outcomes with [[thrombolysis]],<ref name="pmid15495034">{{cite journal |author=Watson L, Armon M |title=Thrombolysis for acute deep vein thrombosis |journal=Cochrane Database Syst Rev |volume= |issue= |pages=CD002783 |year= |id=PMID 15495034}}</ref> there may be an increase in serious bleeding complications. A more recent [[randomized controlled trial]] confirms benefit - specifically reduction in post-thrombotic syndrome after two years.<ref>{{Cite journal
| doi = 10.1016/S0140-6736(11)61753-4
| issn = 01406736
| last = Enden
| first = Tone
| coauthors = Ylva Haig, Nils-Einar Kløw, Carl-Erik Slagsvold, Leiv Sandvik, Waleed Ghanima, Geir Hafsahl, Pål Andre Holme, Lars Olaf Holmen, Anne Mette Njaastad, Gunnar Sandbæk, Per Morten Sandset
| title = Long-term outcome after additional catheter-directed thrombolysis versus standard treatment for acute iliofemoral deep vein thrombosis (the CaVenT study): a randomised controlled trial
| journal = The Lancet
| accessdate = 2011-12-15
| date = 2011-12
| url = http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2811%2961753-4/abstract
}}</ref> [[Clinical practice guideline]]s address the management of severe forms of [[embolism and thrombosis]] which may require [[thrombolysis]].<ref  name="pmid21422387">{{cite journal| author=Jaff MR, McMurtry MS,  Archer SL, Cushman M, Goldenberg N, Goldhaber SZ et al.|  title=Management of Massive and Submassive Pulmonary Embolism,  Iliofemoral Deep Vein Thrombosis, and Chronic Thromboembolic Pulmonary  Hypertension: A Scientific Statement From the American Heart  Association. | journal=Circulation | year= 2011 | volume=  | issue=  |  pages=  | pmid=21422387 | doi=10.1161/CIR.0b013e318214914f | pmc= |  url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21422387  }} </ref>
* [[Anticoagulation]] is the usual treatment for DVT.  In general, patients are initiated on a brief course (i.e., less than a week) of [[heparin]] treatment while they start on a 3- to 6-month course of [[warfarin]] (or related [[vitamin K]] inhibitors).  [[Low molecular weight heparin]] (LMWH) is preferred,<ref name="pmid0000">{{cite journal |author=Snow V et al |title=Management of Venous Thromboembolism: A Clinical Practice Guideline from the American College of Physicians and the American Academy of Family Physicians |journal=Ann Intern Med |volume= 146 |issue=  3|pages= |year= 2007  | url = http://www.annals.org/cgi/content/full/0000605-200702060-00149v1}}</ref> though unfractionated [[heparin]] is given in patients who have a contraindication to LMWH (e.g., renal failure or imminent need for invasive procedure). [[Rivaroxaban]] may provide oral treatment.<ref name="pmid18621928">{{cite journal |author=Buller HR, Lensing AW, Prins MH, ''et al'' |title=A dose-ranging study evaluating once-daily oral administration of the factor Xa inhibitor rivaroxaban in the treatment of patients with acute symptomatic deep vein thrombosis: the Einstein-DVT Dose-Ranging Study |journal=Blood |volume=112 |issue=6 |pages=2242–7 |year=2008 |month=September |pmid=18621928 |doi=10.1182/blood-2008-05-160143 |url=http://www.bloodjournal.org/cgi/pmidlookup?view=long&pmid=18621928 |issn=}}</ref>


* [[Anticoagulation]] is the usual treatment for DVT.  In general, patients are initiated on a brief course (i.e., less than a week) of [[heparin]] treatment while they start on a 3- to 6-month course of [[warfarin]] (or related [[vitamin K]] inhibitors).  [[Low molecular weight heparin]] (LMWH) is preferred,<ref name="pmid0000">{{cite journal |author=Snow V et al |title=Management of Venous Thromboembolism: A Clinical Practice Guideline from the American College of Physicians and the American Academy of Family Physicians |journal=Ann Intern Med |volume= 146 |issue=  3|pages= |year= 2007  | url = http://www.annals.org/cgi/content/full/0000605-200702060-00149v1}}</ref> though unfractionated [[heparin]] is given in patients who have a contraindication to LMWH (e.g., renal failure or imminent need for invasive procedure).  In patients who have had ''recurrent DVTs'' (two or more), anticoagulation is generally "life-long."  The [[Cochrane Collaboration]] has meta-analyzed the risk and benefits of prolonged anti-coagulation.<ref name="pmid16437432">{{cite journal |author=Hutten BA, Prins MH |title=Duration of treatment with vitamin K antagonists in symptomatic venous thromboembolism |journal=Cochrane database of systematic reviews (Online) |volume= |issue=1 |pages=CD001367 |year=2006 |pmid=16437432 |doi=10.1002/14651858.CD001367.pub2}}</ref>
:Regarding the duration of [[anticoagulation]], see [[embolism and thrombosis#treatment|embolism and thrombosis: treatment]].


* Elastic compression stockings should be routinely applied.<ref name="pmid0000">.</ref>  The stockings in almost all trials were ''stronger than routine anti-embolism stockings'' and created either 20-30 mm Hg or 30-40 mm Hg.  Most trials used knee-high stockings.  A [[meta-analysis]] of [[randomized controlled trials]] by the [[Cochrane Collaboration]] showed reduced incidence of post-phlebitic syndrome.<ref name="pmid14974060">{{cite journal |author=Kolbach D, Sandbrink M, Hamulyak K, Neumann H, Prins M |title=Non-pharmaceutical measures for prevention of post-thrombotic syndrome |journal=Cochrane Database Syst Rev |volume= |issue= |pages=CD004174 |year= |id=PMID 14974060 | doi = 10.1002/14651858.CD004174.pub2}}</ref> The [[number needed to treat]] is quite potent at 4 to 5 patients need to prevent one case of post-phlebitic syndrome.<ref name="pmid17003920">{{cite journal |author=Kakkos S, Daskalopoulou S, Daskalopoulos M, Nicolaides A, Geroulakos G |title=Review on the value of graduated elastic compression stockings after deep vein thrombosis |journal=Thromb Haemost |volume=96 |issue=4 |pages=441-5 |year=2006 |id=PMID 17003920}}</ref>
* Elastic compression stockings have been strongly encouraged.<ref name="pmid0000"/><ref name="pmid20670728">{{cite journal| author=Musani MH, Matta F, Yaekoub AY, Liang J, Hull RD, Stein PD| title=Venous compression for prevention of postthrombotic syndrome: a meta-analysis. | journal=Am J Med | year= 2010 | volume= 123 | issue= 8 | pages= 735-40 | pmid=20670728 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20670728 | doi=10.1016/j.amjmed.2010.01.027 }} </ref>  The stockings in almost all trials were ''stronger than routine anti-embolism stockings'' and created either 20-30 mm Hg or 30-40 mm Hg.  Most trials used knee-high stockings.  A [[meta-analysis]] of [[randomized controlled trials]] by the [[Cochrane Collaboration]] showed reduced incidence of post-phlebitic syndrome.<ref name="pmid14974060">{{cite journal |author=Kolbach D, Sandbrink M, Hamulyak K, Neumann H, Prins M |title=Non-pharmaceutical measures for prevention of post-thrombotic syndrome |journal=Cochrane Database Syst Rev |volume= |issue= |pages=CD004174 |year=2004 |id=PMID 14974060 | doi = 10.1002/14651858.CD004174.pub2}}</ref> The [[number needed to treat]] is quite potent at 4 to 5 patients need to prevent one case of post-phlebitic syndrome.<ref name="pmid17003920">{{cite journal |author=Kakkos S, Daskalopoulou S, Daskalopoulos M, Nicolaides A, Geroulakos G |title=Review on the value of graduated elastic compression stockings after deep vein thrombosis |journal=Thromb Haemost |volume=96 |issue=4 |pages=441-5 |year=2006 |id=PMID 17003920}}</ref> However, a more recent trial found that prophylactic use of compression stockings after deep venous thrombosis may not prevent [[venous insufficiency]].<ref name="pmid24315521">{{cite journal| author=Kahn SR, Shapiro S, Wells PS, Rodger MA, Kovacs MJ, Anderson DR et al.| title=Compression stockings to prevent post-thrombotic syndrome: a randomised placebo-controlled trial. |journal=Lancet | year= 2013 | volume=  | issue=  | pages=  | pmid=24315521 | doi=10.1016/S0140-6736(13)61902-9 |pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=24315521  }} </ref>Compression stocking can cause local complications.<ref name="pmid19477503">{{cite journal| author=CLOTS Trials Collaboration. Dennis M, Sandercock PA, Reid J, Graham C, Murray G et al.| title=Effectiveness of thigh-length graduated compression stockings to reduce the risk of deep vein thrombosis after stroke (CLOTS trial 1): a multicentre, randomised controlled trial. | journal=Lancet | year= 2009 | volume= 373 | issue= 9679 | pages= 1958-65 | pmid=19477503
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=19477503 | doi=10.1016/S0140-6736(09)60941-7 | pmc=PMC2692021 }}  [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=19841446 Review in: Ann Intern Med. 2009 Oct 20;151(8):JC4-9] <!--Formatted by http://sumsearch.uthscsa.edu/cite/--></ref>


* [[Inferior vena cava filter]] reduces pulmonary embolism<ref name="pmid9459643">{{cite journal |author=Decousus H, Leizorovicz A, Parent F, Page Y, Tardy B, Girard P, Laporte S, Faivre R, Charbonnier B, Barral F, Huet Y, Simonneau G |title=A clinical trial of vena caval filters in the prevention of pulmonary embolism in patients with proximal deep-vein thrombosis.  Prévention du Risque d'Embolie Pulmonaire par Interruption Cave Study Group |journal=N Engl J Med |volume=338 |issue=7 |pages=409-15 |year=1998 |id=PMID 9459643}}</ref> and is an option for patients with an absolute contraindiciation to anticoagulant treatment (e.g., cerebral hemorrhage) or those rare patients who have objectively documented recurrent PEs while on anticoagulation, an [[inferior vena cava filter]] (also referred to as a ''[[Greenfield filter]]'') may prevent pulmonary embolisation of the leg clot.  However these filters are themselves potential foci of thrombosis,<ref name="pmid16009794">{{cite journal |author= |title=Eight-year follow-up of patients with permanent vena cava filters in the prevention of pulmonary embolism: the PREPIC (Prevention du Risque d'Embolie Pulmonaire par Interruption Cave) randomized study |journal=Circulation |volume=112 |issue=3 |pages=416-22 |year=2005 |id=PMID 16009794}}</ref> IVC filters are viewed as a temporizing measure for preventing life-threatening pulmonary embolism.
* Inferior [[vena cava filter]] also referred to as a ''Greenfield filter'',  reduces pulmonary embolism<ref name="pmid9459643">{{cite journal |author=Decousus H, Leizorovicz A, Parent F, Page Y, Tardy B, Girard P, Laporte S, Faivre R, Charbonnier B, Barral F, Huet Y, Simonneau G |title=A clinical trial of vena caval filters in the prevention of pulmonary embolism in patients with proximal deep-vein thrombosis.  Prévention du Risque d'Embolie Pulmonaire par Interruption Cave Study Group |journal=N Engl J Med |volume=338 |issue=7 |pages=409-15 |year=1998 |id=PMID 9459643}}</ref> and is an option for patients with an absolute contraindication to anticoagulant treatment (e.g., cerebral hemorrhage) or those rare patients who have objectively documented recurrent PEs while on [[anticoagulation]].  However these filters are themselves potential foci of thrombosis,<ref name="pmid16009794">{{cite journal| author=PREPIC Study Group| title=Eight-year follow-up of patients with permanent vena cava filters in the prevention of pulmonary embolism: the PREPIC (Prevention du Risque d'Embolie Pulmonaire par Interruption Cave) randomized study. | journal=Circulation | year= 2005 | volume= 112 | issue= 3 | pages= 416-22 | pmid=16009794
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=clinical.uthscsa.edu/cite&email=badgett@uthscdsa.edu&retmode=ref&cmd=prlinks&id=16009794 | doi=10.1161/CIRCULATIONAHA.104.512834 }} [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=clinical.uthscsa.edu/cite&email=badgett@uthscdsa.edu&retmode=ref&cmd=prlinks&id=16388567 Review in: ACP J Club. 2006 Jan-Feb;144(1):18] <!--Formatted by http://sumsearch.uthscsa.edu/cite/--></ref> IVC filters are viewed as a temporizing measure for preventing life-threatening pulmonary embolism.


* Hospitalization should be considered in patients with more than two of the following risk factors as these patients may have more risk of complications during treatment<ref name="pmid16926081">{{cite journal |author=Trujillo-Santos J, Herrera S, Page MA, ''et al'' |title=Predicting adverse outcome in outpatients with acute deep vein thrombosis. findings from the RIETE Registry |journal=J. Vasc. Surg. |volume=44 |issue=4 |pages=789-93 |year=2006 |pmid=16926081 |doi=10.1016/j.jvs.2006.06.032}}</ref>:
* Hospitalization should be considered in patients with more than two of the following risk factors as these patients may have more risk of complications during treatment<ref name="pmid16926081">{{cite journal |author=Trujillo-Santos J, Herrera S, Page MA, ''et al'' |title=Predicting adverse outcome in outpatients with acute deep vein thrombosis. findings from the RIETE Registry |journal=J. Vasc. Surg. |volume=44 |issue=4 |pages=789-93 |year=2006 |pmid=16926081 |doi=10.1016/j.jvs.2006.06.032}}</ref>:
** bilateral DVT, renal insufficiency, body weight <70 kg, recent immobility, chronic heart failure, and cancer
** bilateral DVT, renal insufficiency, body weight <70 kg, recent immobility, chronic heart failure, and cancer


==Prophylaxis (Prevention)==
===Oncology patients===
[[Clinical practice guidelines]] by the American College of Chest Physicians (ACCP) provide recommendations on DVT prophylaxis in hospitalized patients <ref name="pmid15383478">Geerts WH, Pineo GF, Heit JA, Bergqvist D, Lassen MR, Colwell CW, Ray JG. Prevention of venous thromboembolism: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy.
A [[clinical practice guideline]] published in 2004 by the [[American College of Chest Physicians]] states:<ref name="pmid15383479">{{cite journal |author=Büller HR, Agnelli G, Hull RD, Hyers TM, Prins MH, Raskob GE |title=Antithrombotic therapy for venous thromboembolic disease: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy |journal=Chest |volume=126 |issue=3 Suppl |pages=401S–428S |year=2004 |pmid=15383479 |doi=10.1378/chest.126.3_suppl.401S |issn=}}</ref>
Chest. 2004 Sep;126 (3 Suppl):338S-400S. http://www.chestjournal.org/cgi/content/full/126/3_suppl/338S PMID 15383478</ref>.
:"for patients with DVT and cancer, we recommend LMWH for the first 3 to 6 months of long-term anticoagulant therapy (Grade 1A). For these patients, we recommend anticoagulant therapy indefinitely or until the cancer is resolved".


===General Medical Inpatients===
A [[clinical practice guideline]] published in 2007 by the [[American Society of Clinical Oncology]] states:<ref name="pmid17968019"/>
Regarding general medical inpatients the guidelines state, "In acutely ill medical patients who have been admitted to the hospital with congestive heart failure or severe respiratory disease, or who are confined to bed and have one or more additional risk factors, including active cancer, previous VTE, [[sepsis]], acute neurologic disease, or inflammatory bowel disease, we recommend prophylaxis with LDUH (Grade 1A) or LMWH (Grade 1A)<ref name="pmid15383478">.</ref>." Enoxaparin or unfractionated heparin may be used.<ref>{{cite journal|title=Twice vs three times daily heparin dosing for thromboembolism prophylaxis in the general medical population: A metaanalysis|author=King CS, Holley AB, Jackson JL, Shorr AF, Moores LK|journal=Chest|year=2007|volume=131|issue=2|pages=507&ndash;16|pmid=17296655}}</ref> LMWH may be more effective than UFH. If UFH heparin is used, 5000 U 3 times daily may be more effective<ref name="pmidpending">Wein L et al. [http://archinte.ama-assn.org/cgi/content/full/167/14/1476 Pharmacological Venous Thromboembolism Prophylaxis in Hospitalized Medical Patients]. Arch Intern med 2007;167:1476-1486.</ref>
:"1) low molecular weight heparin LMWH is the preferred approach for the initial 5 to 10 days of anticoagulant treatment of the cancer patient with established VTE, 2) LMWH given for at least 6 months is also the preferred approach for long-term anticoagulant therapy. Vitamin K antagonists with a targeted INR of 2 to 3 are acceptable for long-term therapy when LMWH is not available. 3) After 6 months, indefinite anticoagulant therapy should be considered for selected patients with active cancer, such as those with metastatic disease and those receiving chemotherapy. This recommendation is based on Panel consensus in the absence of clinical trials data."


Since publication of the ACCP guidelines, an additional [[randomized controlled trial]] <ref name="pmid16431185">Lederle FA, Sacks JM, Fiore L, Landefeld CS, Steinberg N, Peters RW, Eid AA, Sebastian J, Stasek JE Jr, Fye CL. The prophylaxis of medical patients for thromboembolism pilot study. Am J Med. 2006;119:54-9. PMID 16431185</ref> and [[meta-analysis]] <ref name="pmid17310052">Dentali F, Douketis JD, Gianni M, Lim W, Crowther MA.  [http://annals.org/cgi/content/full/146/4/278 Meta-analysis: anticoagulant prophylaxis to prevent symptomatic venous thromboembolism in hospitalized medical patients]. Ann Intern Med. 2007;146:278-88. PMID 17310052</ref> including the trial have been published. The [[meta-analysis]] concluded " Anticoagulant prophylaxis is effective in preventing symptomatic venous thromboembolism during anticoagulant prophylaxis in at-risk hospitalized medical patients. Additional research is needed to determine the risk for venous thromboembolism in these patients after prophylaxis has been stopped." With regards to which patients are at risk, most studies in the meta-analysis were of patients with  [[New York Heart Association Functional Classification]] (NYHA) III-IV heart failure. Regarding patients at lesser risk of DVT, the trial above<ref name="pmid16431185"/> and an earlier trial<ref name="pmid8637340">{{cite journal |author=Gärdlund B |title=Randomised, controlled trial of low-dose heparin for prevention of fatal pulmonary embolism in patients with infectious diseases. The Heparin Prophylaxis Study Group |journal=Lancet |volume=347 |issue=9012 |pages=1357–61 |year=1996 |pmid=8637340 |doi= |issn=}}</ref> are relevant yet inconclusive.
===Determining when to stop treatment===
====D-Dimer====
An abnormal [[D-dimer]] level at the end of treatment might signal the need for continued [[anticoagulation]] with [[warfarin]] among patients with [[embolism and thrombosis]] such as a first unprovoked [[pulmonary embolism]].<ref name="pmid20956709">{{cite journal| author=Douketis J, Tosetto A, Marcucci M, Baglin T, Cushman M, Eichinger S et al.| title=Patient-level meta-analysis: effect of measurement timing, threshold, and patient age on ability of D-dimer testing to assess recurrence risk after unprovoked venous thromboembolism. | journal=Ann Intern Med | year= 2010 | volume= 153 | issue= 8 | pages= 523-31 | pmid=20956709 | doi=10.1059/0003-4819-153-8-201010190-00009 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20956709  }} </ref> If the D-dimer is abnormal, anticoaguation should be continued, if the D-dimer is normal, the duration of treatment is uncertain.<ref name="pmid17065639">{{cite journal |author=Palareti G, Cosmi B, Legnani C, ''et al'' |title=D-dimer testing to determine the duration of anticoagulation therapy |journal=N. Engl. J. Med. |volume=355 |issue=17 |pages=1780-9 |year=2006 |pmid=17065639 |doi=10.1056/NEJMoa054444}}</ref> In an observation study that collected the D-dimer before stopping anticoagulation, the D-dimer was not as predictive.<ref>Rodger MA, Kahn SR, Wells PS, Anderson DA, Chagnon I, Le Gal G, et al. [Identifying unprovoked thromboembolism patients at low risk for recurrence who can discontinue anticoagulant therapy http://www.cmaj.ca/cgi/content/full/179/5/417]. CMAJ. 2008 Aug 26;179(5):417-426.</ref>


===Oncology patients===
====Ultrasonography====
According to a [[clinical practice guideline]] by the American Society of Clinical Oncology, "all hospitalized cancer patients should be considered for VTE prophylaxis with anticoagulants in the absence of bleeding or other contraindications."<ref name="pmid17968019">{{cite journal |author=Lyman GH, Khorana AA, Falanga A, ''et al'' |title=American Society of Clinical Oncology Guideline: Recommendations for Venous Thromboembolism Prophylaxis and Treatment in Patients With Cancer |journal= |volume= |issue= |pages= |year=2007 |pmid=17968019 |doi=10.1200/JCO.2007.14.1283 |issn=}}</ref>
[[Ultrasonography]], using the following protocol may<ref name="pmid19414836">{{Cite journal | volume = 150 | issue = 9 | pages = 577-585 | last = Prandoni | first = Paolo | coauthors = Martin H. Prins, Anthonie W.A. Lensing, Angelo Ghirarduzzi, Walter Ageno, Davide Imberti, Gianluigi Scannapieco, Giovanni B. Ambrosio, Raffaele Pesavento, Stefano Cuppini, Roberto Quintavalla, Giancarlo Agnelli, for the AESOPUS Investigators | title = Residual Thrombosis on Ultrasonography to Guide the Duration of Anticoagulation in Patients With Deep Venous Thrombosis: A Randomized Trial | journal = Ann Intern Med | accessdate = 2009-05-06 | date = 2009-05-05 | pmid=19414836 |url = http://www.annals.org/cgi/content/abstract/150/9/577}}</ref> or may not<ref name="pmid9313000">{{cite journal |author=Robinson KS, Anderson DR, Gross M, ''et al.'' |title=Ultrasonographic screening before hospital discharge for deep venous thrombosis after arthroplasty: the post-arthroplasty screening study. A randomized, controlled trial |journal=Ann. Intern. Med. |volume=127 |issue=6 |pages=439–45 |year=1997 |month=September |pmid=9313000 |doi= |url=http://www.annals.org/cgi/pmidlookup?view=long&pmid=9313000 |issn=}}</ref> help determine when to stop anticoaguation<ref name="pmid19414836"/>:
:"If veins had not recanalized, we invited patients to have further ultrasonography after 3 and 9 months in patients with secondary DVT and after 3, 9, 15, and 21 months in those with unprovoked DVT. Anticoagulation was discontinued when the veins had recanalized, along with further ultrasonography"


===Surgery Patients===
==Prognosis==
In patients who have undergone [[surgery]], [[low molecular weight heparin]]s (LMWH) are routinely administered to prevent thrombosis.  LMWH can only currently be administered subcutaneously by injection.  Prophylaxis for pregnant women who have a history of thrombosis may be limited to LMWH injections or may not be necessary if their risk factors are mainly temporary.
{| class="wikitable"
|+ Reducing the risk of recurrence after an unprovoked [[deep venous thrombosis]].<ref name="pmid22621626">{{cite journal|  author=Becattini C, Agnelli G, Schenone A, Eichinger S, Bucherini E,  Silingardi M et al.| title=Aspirin for preventing the recurrence of  venous thromboembolism. | journal=N Engl J Med | year= 2012 | volume=  366 | issue= 21 | pages= 1959-67 | pmid=22621626 |  doi=10.1056/NEJMoa1114238 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22621626  }} </ref> <ref name="pmid21128814">{{cite journal|  author=EINSTEIN Investigators. Bauersachs R, Berkowitz SD, Brenner B,  Buller HR, Decousus H et al.| title=Oral rivaroxaban for symptomatic  venous thromboembolism. | journal=N Engl J Med | year= 2010 | volume=  363 | issue= 26 | pages= 2499-510 | pmid=21128814 |  doi=10.1056/NEJMoa1007903 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21128814  }}  [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21460399 Review in: Evid Based Med. 2011 Oct;16(5):139-40] </ref> <ref name="pmid20956709"/> <ref name="pmid21382171">{{cite journal|  author=Carrier M, Rodger MA, Wells PS, Righini M, LE Gal G|  title=Residual vein obstruction to predict the risk of recurrent venous  thromboembolism in patients with deep vein thrombosis: a systematic  review and meta-analysis. | journal=J Thromb Haemost | year= 2011 | volume= 9 | issue= 6 | pages= 1119-25 | pmid=21382171 |  doi=10.1111/j.1538-7836.2011.04254.x | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21382171  }} </ref> <ref name="pmid22489957">{{cite journal|  author=Tosetto A, Iorio A, Marcucci M, Baglin T, Cushman M, Eichinger S  et al.| title=Predicting disease recurrence in patients with previous  unprovoked venous thromboembolism: a proposed prediction score (DASH). | journal=J Thromb Haemost | year= 2012 | volume= 10 | issue= 6 | pages=  1019-25 | pmid=22489957 | doi=10.1111/j.1538-7836.2012.04735.x | pmc= |  url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22489957  }} </ref>
! &nbsp;!! Treatment or test!!Risk if treated or test result is favorable!!Risk if ''not treated'' or test result is ''unfavorable''!!Comments
|-
| [[Randomized controlled trial]]<ref name="pmid22621626"/>|| Aspirin 100 mg daily for 2 years||6% per year||11.2% per year||0.5% major bleeding
|-
| [[Randomized controlled trial]]<ref name="pmid21128814"/>|| Rivaroxaban for 6-12 months||1% over 6-12 months||7% over 6-12 months||0.7% major bleeding
|-
| [[Systematic review]] of a [[diagnostic test]]<ref name="pmid20956709"/><ref name="pmid22489957"/>|| Normal [[d-dimer]]||4% per year||9% per year
|-
| [[Systematic review]] of a [[diagnostic test]]<ref name="pmid21382171"/>|| Recanalization of veins (no residual vein obstruction or RVO)||colspan="2" align="center"|Insignificant difference
|}


Early and regular ambulation (walking) is a treatment that predates anticoagulants and is still recognized and used today.  Walking activates the body's muscle pumps, increasing venous velocity and preventing [[stasis]].  [[Intermittent pneumatic compression]] (IPC) machines have proven protective in bed- or chair-ridden patients at very high risk or with contraindications to heparins.  IPC machines use air bladders that are wrapped around the thigh and/or calf. The bladders alternately inflate and deflate, squeezing the muscles and increasing blood velocity by as much as 500%. IPC machines have been proven effective on knee and hip surgery patients (a population with a risk as high as 80% with no prophylactic treatment) of developing DVT and PE.
===Postthrombotic syndrome===
Alternatively, between 150-300mg of aspirin can be taken.
[[Postthrombotic syndrome]] along with [[postphlebitic syndrome]] are forms of [[venous insufficiency]].  Postthrombotic syndrome is a "condition caused by one or more episodes of deep vein thrombosis, usually the blot clots are lodged in the legs. Clinical features include [[edema]]; [[pain]]; aching; heaviness; and muscle cramp in the leg. When severe leg swelling leads to skin breakdown, it is called [[venous stasis ulcer]]."<ref>{{MeSH|Postthrombotic syndrome}}</ref><ref name="pmid16885552">{{cite journal |author=Bergan JJ, Schmid-Schönbein GW, Smith PD, Nicolaides AN, Boisseau MR, Eklof B |title=Chronic venous disease |journal=N. Engl. J. Med. |volume=355 |issue=5 |pages=488–98 |year=2006 |month=August |pmid=16885552 |doi=10.1056/NEJMra055289 |url=http://content.nejm.org/cgi/pmidlookup?view=short&pmid=16885552 |issn=}}</ref>


===Travelers===
The incidence of postthrombotic syndrome is 76.1 per 100,000 person-years.<ref name="pmid11331844">{{cite journal |author=Heit JA, Rooke TW, Silverstein MD, ''et al'' |title=Trends in the incidence of venous stasis syndrome and venous ulcer: a 25-year population-based study |journal=J. Vasc. Surg. |volume=33 |issue=5 |pages=1022–7 |year=2001 |month=May |pmid=11331844 |doi=10.1067/mva.2001.113308 |url=http://linkinghub.elsevier.com/retrieve/pii/S0741-5214(01)33636-4 |issn=}}</ref> Regarding the etiology of the postthrombotic syndrome, about 40% are from prior DVT<ref name="pmid3613024">{{cite journal |author=Train JS, Schanzer H, Peirce EC, Dan SJ, Mitty HA |title=Radiological evaluation of the chronic venous stasis syndrome |journal=JAMA |volume=258 |issue=7 |pages=941–4 |year=1987 |month=August |pmid=3613024 |doi= |url= |issn=}}</ref> although only 25% of patients report a prior diagnosis of DVT<ref name="pmid11331844">{{cite journal |author=Heit JA, Rooke TW, Silverstein MD, ''et al'' |title=Trends in the incidence of venous stasis syndrome and venous ulcer: a 25-year population-based study |journal=J. Vasc. Surg. |volume=33 |issue=5 |pages=1022–7 |year=2001 |month=May |pmid=11331844 |doi=10.1067/mva.2001.113308 |url=http://linkinghub.elsevier.com/retrieve/pii/S0741-5214(01)33636-4 |issn=}}</ref>. This suggests nearly half of the prior DVTs were undiagnosed.
{{main|Economy class syndrome}}
There is clinical evidence to suggest that wearing compression socks while travelling also reduces the incidence of thrombosis in people on long haul flights. A randomised study in 2001 compared two sets of long haul airline passengers, one set wore travel compression hosiery the others did not. The passengers were all scanned and blood tested to check for the incidence of DVT. The results showed that asymptomatic DVT occurred in 10% of the passengers who did not wear compression socks. The group wearing compression had no DVTs. The authors concluded that wearing elastic compression hosiery reduces the incidence of DVT in long haul airline passengers.<ref>Scurr JH, Machin SJ, Bailey-King S, Mackie IJ, McDonald S, Smith PD. Frequency and prevention of symptomless deep-vein thrombosis in long-haul flights: a randomised trial. ''[[The Lancet|Lancet]] 2001;12(9267):1485-9. PMID 11377600.</ref>.


==Pathogenesis==
;Natural history of a diagnosed DVT
{{main|Thrombosis}}
The natural history of a diagnosed DVT is as follows. After two years, the probability of postthrombotic syndrome is:<ref>{{Cite journal | volume = 149 | issue = 10 | pages = 698-707 | last = Kahn | first = Susan R. | coauthors = Ian Shrier, Jim A. Julian, Thierry Ducruet, Louise Arsenault, Marie-Jose Miron, Andre Roussin, Sylvie Desmarais, France Joyal, Jeannine Kassis, Susan Solymoss, Louis Desjardins, Donna L. Lamping, Mira Johri, Jeffrey S. Ginsberg | title = Determinants and Time Course of the Postthrombotic Syndrome after Acute Deep Venous Thrombosis | journal = Ann Intern Med | accessdate = 2008-11-18 | date = 2008-11-18 | url = http://www.annals.org/cgi/content/abstract/149/10/698 }}</ref>
* No postthrombotic syndrome 60%
* Mild postthrombotic syndrome 26%
* Moderate postthrombotic syndrome 11%
* Severe postthrombotic syndrome 3%


Many factors are involved in the formation of a thrombus (clot).  [[Virchow's triad]] is a group of 3 factors known to affect clot formation: rate of flow, the consistency (thickness) of the blood, and qualities of the vessel wall.  Among the risk factors are advanced age, obesity, infection, immobilization, female sex, use of [[oral contraceptive]]s, tobacco usage and [[air travel]] ("[[economy class syndrome]]", a combination of immobility and relative dehydration) are some of the better-known causes.<ref>{{cite journal | author = Tsai A, Cushman M, Rosamond W, Heckbert S, Polak J, Folsom A | title = Cardiovascular risk factors and venous thromboembolism incidence: the longitudinal investigation of thromboembolism etiology. | journal = Arch Intern Med | volume = 162 | issue = 10 | pages = 1182-9 | year = 2002 | id = PMID 12020191}}</ref>  [[Thrombophilia]] (tendency to develop thrombosis) often expresses itself with recurrent thromboses.
Risk factors include:
* Prior ipsilateral DVT
* Obesity
* Female gender
* Older age


It is recognised that thrombi usually develop first in the calf veins, "growing" in the direction of flow of the vein. DVTs are distinguished as being above or below the [[popliteal]] vein. Very extensive DVTs can extend into the [[iliac vein]]s or the [[inferior vena cava]]. The risk of pulmonary embolism is higher in the presence of more extensive clots.
After 5 to 10 years:
One cohort reported 28% incidence (using a definition that required more significant symptoms)at five years.<ref name="pmid8644983">{{cite journal |author=Prandoni P, Lensing AW, Cogo A, ''et al'' |title=The long-term clinical course of acute deep venous thrombosis |journal=Ann. Intern. Med. |volume=125 |issue=1 |pages=1–7 |year=1996 |month=July |pmid=8644983 |doi= |url=http://www.annals.org/cgi/pmidlookup?view=long&pmid=8644983 |issn=}}</ref>


==Epidemiology==
Among patients 6 to 8 years after a DVT, two studies provide risks:
DVTs occur in about 1 per 1000 persons per year. About 1-5% will die from the complications (i.e. [[pulmonary embolism]]).
* "42% reported pain, swelling, or discoloration."<ref name="pmid7748045">{{cite journal |author=Beyth RJ, Cohen AM, Landefeld CS |title=Long-term outcomes of deep-vein thrombosis |journal=Arch. Intern. Med. |volume=155 |issue=10 |pages=1031–7 |year=1995 |month=May |pmid=7748045 |doi= |url= |issn=}}</ref>
* A second study found 70% risk at 8 years.<ref name="pmid16009794"/>


DVT is much less common in the pediatric population. About 1 in 100,000 people under the age of 18 experiences deep vein thrombosis, possibly due to a child's high rate of heartbeats per minute, relatively active lifestyle when compared with adults, and fewer comorbodities (e.g. malignancy).
After 10 to 20 years:
Although after 20 years, only 26.8% of patients will have sought medical care and be diagnosed with late complications of DVT<ref name="pmid11126832">{{cite journal |author=Mohr DN, Silverstein MD, Heit JA, Petterson TM, O'Fallon WM, Melton LJ |title=The venous stasis syndrome after deep venous thrombosis or pulmonary embolism: a population-based study |journal=Mayo Clin. Proc. |volume=75 |issue=12 |pages=1249–56 |year=2000 |month=December |pmid=11126832 |doi= |url= |issn=}}</ref>, when patients are actively studied 10-20 years after their initial thrombosis, 80% have some signs of postthrombotic syndrome.<ref name="pmid11342203">{{cite journal |author=Ziegler S, Schillinger M, Maca TH, Minar E |title=Post-thrombotic syndrome after primary event of deep venous thrombosis 10 to 20 years ago |journal=Thromb. Res. |volume=101 |issue=2 |pages=23–33 |year=2001 |month=January |pmid=11342203 |doi=10.1016/S0049-3848(00)00370-4  |url=http://linkinghub.elsevier.com/retrieve/pii/S0049-3848(00)00370-4 |issn=}}</ref>


==See also==
===Recurrent DVT===
*[[Venogram (medical)]]
Risk factors for recurrence if [[anticoagulation]] is stopped are:<ref name="pmid18725614">{{cite journal |author=Rodger MA, Kahn SR, Wells PS, ''et al'' |title=Identifying unprovoked thromboembolism patients at low risk for recurrence who can discontinue anticoagulant therapy |journal=CMAJ |volume=179 |issue=5 |pages=417–26 |year=2008 |month=August |pmid=18725614 |pmc=2518177 |doi=10.1503/cmaj.080493 |url=http://www.cmaj.ca/cgi/pmidlookup?view=long&pmid=18725614 |issn=}}</ref>
* post-thrombotic  symptoms such as "hyperpigmentation, edema or redness of either leg"
* [[D-dimer]] > or = 250 microg/L while taking [[warfarin]]> Other studies suggest the D-dimer should be checked after stopping warfarin.
* [[body mass index]] > or = 30 kg/m(2)
* age > or = 65 years
* male gender


==References==
==References==
{{Reflist|2}}
<small>
 
<references>
==External links==
*[http://www.clotcare.com/clotcare/dvt.aspx Deep Vein Thrombosis (DVT) Prevention, Treatment, Diagnosis, & Related Issues] - ClotCare.com
*[http://www.dvt.net/ Deep Vein Thrombosis (DVT) Blood Clot Prevention, Treatment, and More] - DVT.net
*[http://www.whonamedit.com/synd.cfm/1924.html Paget-von Schrötter disease] - whonamedit.com
*[http://www.emedicine.com/emerg/topic122.htm DVT] - emedicine.com
*[http://www.anticoagulationeurope.org/welcome.html AntiCoagulation Europe] - AntiCoagulation Europe is a charity providing information and advice to people on oral anticoagulation therapy
*[http://www.preventdvt.org/ Prevent DVT Coalition]
*[http://www.jscurr.com/StudySummary.htm J Scurr Lancet study summary]
*[http://www.mediuk-travel.co.uk/clinical_evidence.html mediUK DVT prevention during travel, the clinical evidence]
*[http://www.varda.org Victims of Air Related DVT Association]


[[Category:CZ Live]] [[Category:Health Sciences Workgroup]]
</references>
</small>

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Deep vein thrombosis (DVT), also known as deep-venous thrombosis, is the formation of a blood clot ("thrombus") in a deep vein. It commonly affects the leg veins, such as the femoral vein or the popliteal vein or the deep veins of the pelvis. Occasionally the veins of the arm are affected (known as Paget-Schrötter disease). Embolism and thrombosis is the more general class of pathologies of this kind.

Thrombi may develop first in the calf veins (calf vein thrombosis), "growing" in the direction of flow of the vein. DVTs are distinguished as being above or below the trifucation of the popliteal vein. Very extensive DVTs can extend into the iliac veins or the inferior vena cava. The risk of pulmonary embolism is higher in the presence of more extensive clots.

Epidemiology

DVTs occur in about 1 per 1000 persons per year. About 1-5% will die from the complications (i.e. pulmonary embolism).

DVT is much less common in the pediatric population. About 1 in 100,000 people under the age of 18 experiences deep vein thrombosis, possibly due to a child's high rate of heartbeats per minute, relatively active lifestyle when compared with adults, and fewer comorbodities (e.g. malignancy).

Medical inpatients at risk of DVT can be identified with clinical prediction rules.[1][2]

Predicting which medical inpatients will develop DVT.[1][2]
  heading
RAM[1] prior VTE
order for bed rest
PICC insertion
cancer
Kucher score[2]

Cancer 3 points
Prior VTE 3
Hypercoagulability 3
Major surgery 2
Bed rest 1
Age >70 years 1
Obesity (BMI >30) 1
Estrogens 1

Cause/etiology

Virchow's triad

Many factors are involved in the formation of a thrombus (clot). Virchow's triad is a group of 3 factors known to affect clot formation: rate of flow, the consistency (thickness) of the blood, and qualities of the vessel wall. Among the risk factors are advanced age, obesity, infection, immobilization, female sex, use of oral contraceptives, tobacco usage and air travel ("economy class syndrome", a combination of immobility and relative dehydration) are some of the better-known causes.[3] Thrombophilia (tendency to develop thrombosis) often expresses itself with recurrent thromboses.

Underlying malignancy

DVT may be due to underlying malignancy, especially if the DVT is associated with older age, idiopathic DVT, bilateral thrombosis, or anemia.[4] These patients have a worse prognosis.

Genetics

A twin study found a genetic contribution to venous thromboembolism among men but not women.[5] Among men, the concordance rates for mono- and dizygotic twin pairs were 0.22 and 0.08.

Various single-nucleotide polymorphisms (SNPs) have been associated with DVT.[6]

Signs and symptoms

There may be no symptoms referrable to the location of the DVT, but the classical symptoms of DVT include pain, swelling and redness of the leg and dilatation of the surface veins. In up to 25% of all hospitalized patients, there may be some form of DVT, which often remains clinically inapparent (unless pulmonary embolism develops).

There are several techniques during physical examination to increase the detection of DVT, such as measuring the circumference of the affected and the contralateral limb at a fixed point (to objectivate edema), and palpating the venous tract, which is often tender. Physical examination is unreliable for excluding the diagnosis of deep vein thrombosis.

A careful history has to be taken considering risk factors (see below), including the use of estrogen-containing methods of hormonal contraception, recent long-haul flying, and a history of miscarriage (which is a feature of several disorders that can also cause thrombosis). A family history can reveal a hereditary factor in the development of DVT.

It is vital that the possibility of pulmonary embolism be included in the history, as this may warrant further investigation (see pulmonary embolism).

Complications As a complication, post-thrombotic syndrome can develop. Post-phlebitic syndrome occurs in 10% of patients with deep vein thrombosis (DVT). It presents with leg oedema, pain, nocturnal cramping, venous claudication, skin pigmentation, dermatitis and ulceration (usually on the medial aspect of the lower leg). In phlegmasia alba dolens, the leg is pale and cool with a diminished arterial pulse due to spasm. It usually results from acute occlusion of the iliac and femoral veins due to DVT. In phlegmasia cerulea dolens, there is an acute and nearly total venous occlusion of the entire extremity outflow, including the iliac and femoral veins. The leg is usually painful, cyanosed and oedematous. Venous gangrene may supervene.

Diagnosis

Homan's sign is used in clinical practice to diagnose DVT.

The gold standard is intravenous venography, which involves injecting a peripheral vein of the affected limb with a contrast agent and taking X-rays, to reveal whether the venous supply has been obstructed. Because of its invasiveness, this test is rarely performed.

Impedance plethysmography and Doppler ultrasonography are non-invasive alternatives.

Probability scoring for lower extremity DVT

Wells rule

The best studied clinical prediction rule is the Wells rule; however, use of the Wells rule is complicated by the rule having been modified over time. For example, in a recent review, the version of the Wells rule used in the articles was not clear although studies were published over a range of years.[7] This has resulted in guidelines recommending use of outdated versions of the Wells rule.[8] The rule was introduced in 1995.[9]

2003[10]-2006[11] Wells 10 point rule:
  1. Active cancer (treatment within last 6 months or palliative) -- 1 point
  2. Calf swelling >3cm compared to other calf (measured 10cm below tibial tuberosity) -- 1 point
  3. Collateral superficial veins (non-varicose) -- 1 point
  4. Pitting edema (confined to symptomatic leg) -- 1 point
  5. Swelling of entire leg - 1 point
  6. Localized pain along distribution of deep venous system -- 1 point
  7. Paralysis, paresis, or recent cast immobilization of lower extremities -- 1 point
  8. Recently bedridden > 3 days, or major surgery requiring regional or general anesthetic in past 12 weeks -- 1 point
  9. Previously documented DVT -- 1 point
  10. Alternative diagnosis at least as likely -- Subtract 2 points

Interpretation:

Score of 2 or higher - deep vein thrombosis is likely. Consider imaging the leg veins.
Score of less than 2 - deep vein thrombosis is unlikely. Consider blood test such as d-dimer test to further rule out deep vein thrombosis.

2003 Wells 10 point rule:In 2003, Wells published a 10 point rule that adds a point for history of previous DVT (yellow box).[10] In 2006, Wells reviewed the available clinical prediction rules for DVT and did not further modify the 2003 rule.[11]

Based on his 2003 study, Wells recommends that DVT is excluded only when the 10-point score is < 2 and the D-dimer is negative.[11] Independent studies validate the Wells 10 point rule.[12][13][7] However, the d-dimer assays vary; for rapid quantitative immunoturbidimetric assays, a cutoff of 1.0 <g/mL is used.[12]

Earlier version: 1995 Original Wells 12 point rule:[9]
Major points

  • Active cancer (treatment ongoing or within previous 6 months or palliative)
  • Paralysis, paresis. or recent plaster irnmobilisation of the lower extremities
  • Recently bedridden >3 days and/or major surgery within 4 weeks
  • Localised tenderness along tl’e distribution of the deep venous system
  • Thigh and calf swollen (should be measured)
  • Calf swelling 3cm >symptornless side (measured 10cm below tibial tuberosity
  • Strong family history of (NT (2 first degree relatives with history of CVI)

Minor points

  • History of recent trauma C 60 days) to the symptomatic leg
  • Pitting oedema; symptomatic leg only
  • Dilated superficial veins (non-varicose) in symptomatic leg only
  • Hospitisation within previous 6 months
  • Erythema

Earlier version: 1997 Wells 9 point rule:[14]

  1. Active cancer (treatment ongoing or within previous 6 months or palliative) - 1 point
  2. Paralysis, paresis, or recent plaster immobilisation of the lower extremities - 1 point
  3. Recently bedridden for more than 3 days or major surgery, within 4 weeks - 1 point
  4. Localised tenderness along the distribution of the deep venous system - 1 point
  5. Entire leg swollen - 1 point
  6. Calf swelling by more than 3 cm when compared with the asymptomatic leg (measured 10 cm below tibial tuberosity) - 1 point
  7. Pitting oedema (greater in the symptomatic leg) - 1 point
  8. Collateral superficial veins (non-varicose) - 1 point
  9. Alternative diagnosis as likely or greater than that of deep-vein thrombosis - subtract 2 points
Interpretation: low (score 0), medium (score of 1 or 2), or high (score 3)

In 2005 a large study found that the 1997 Wells score failed to adequately exclude DVT in primary care patients.[15] Unfortunately, the 2005 study was completed in March, 2003, 6 months prior to publication of the 2003 revision by Wells to his rule in which he added a 10th variable.

AMUSE Primary Care Rule

Because of concerns about the failed study in 2005 of the older, 9-point 1997 Wells rule (not that the current Wells rule has 10 points)[15], the Amsterdam Maastricht Utrecht Study on thromboEmbolism (AMUSE) Investigators developed a rule with 7 clinical variable plus the D-dimer.[16][17] Patients with a score of 3 or less are considered normal; patients with a score of 4 should receive ultrasonography.

  • Use of hormonal contraceptives
  • Active cancer in past 6 mo
  • Surgery in previous month
  • Absence of leg trauma
  • Distention of collateral leg veins
  • Difference in calf circumference ≥ 3 cm (2 points)
  • Abnormal d-dimer assay (6 points)

Patients with score ≥ 4 should receive ultrasonography of the leg.

The AMUSE investigators report that their rule and the Wells 10 variable rule perform similarly.[13] This rule has not been externally validated by independent research groups.

Probability scoring for upper extremity DVT

The Constans Clinical Decision Score may help. Its components are:[18]

  • Venous material present (Centeral venous catheter or pacemaker thread) (1 point)
  • Localized pain (1 point)
  • Unilateral edema (1 point)
  • Other diagnosis at least as plausible (-1 point)

A score of 1 or less, along with negative d-dimer, excluded DVT. Thus, the d-dimer should be checked on every patient suspected of upper extremity DVT.

Imaging the leg veins

Ultrasonography

Compression B-mode ultrasonography[19] scanning of the leg veins, combined with Duplex Doppler ultrasonography[20] (to determine blood flow), can reveal a thrombus.

Distinguishing acute versus chronic thrombosis with Duplex Doppler ultrasonography has been examined in one study of 103 examination in 101 patients:[21]

In this study "no results were false-positive for acute DVT due to the changes of chronic DVT."

Whole leg ultrasonography
Risk outcomes following a single negative whole-leg compression ultrasonography according to a systematic review.[22]
Wells score Death (%) from embolism and thrombosis (95% CI)
All patients 0.7%
Low risk 0.3% (0 to 0.7%)
Intermediate risk 0.8% (0 to 1.8%)
High risk 2.5% (0 to 7.1%)

Either whole leg Doppler ultrasonography or serial 2-point ultrasonography plus D-dimer are equivalent strategies according to a randomized controlled trial[23] that was included in the meta-analysis.

An uncontrolled cohort study found that anticoagulation can be safely withheld in patients with normal whole leg Doppler ultrasonography.[24]

Venography

Venography can determine acute versus chronic thrombosis:[21]

  • Acute thrombosis is suggested by any of:
    • "constant filling defect or thrombus was identified"
    • "persistent nonfilling of a venous segment despite adequate technique"
    • " abrupt termination of the opaque column of contrast material in a venous segment"
  • Chronic thrombosis is suggested by any of:
    • "irregular walls suggestive of retracted adherent thrombus"
    • "a lumen smaller than expected"
    • "numerous well-developed adjacent collateral veins"
    • "Valvular incompetence in the deep veins was considered further evidence of chronic DVT but was not required for the diagnosis."

Blood tests

In a low-probability situation, current practice is to commence investigations by testing for D-dimer levels. A low D dimer level should prompt other possible diagnoses (such as a ruptured Baker's cyst, if this has not been considered as part of the history).

  • D-dimer levels. This cross-linked fibrin degradation product is an indication that thrombosis is occurring, and that the blood clot is being dissolved by plasmin. Interpretation may be increased by using age adjusted levels:[25]
    • "In patients younger than 50 years, PE was excluded in those with a D-dimer value lower than 500 µg/L.{"
    • "In patients 50 years or older, the D-dimer test result was considered negative in those with a D-dimer value lower than their age multiplied by 10."

Other blood tests usually performed at this point are:

Differential diagnosis

Rupture of the tendon of the plantaris muscle[26] 

may mimic deep venous thrombosis.[27]

Prophylaxis (Prevention)

General Medical Inpatients

Clinical practice guidelines state:

  • American College of Physicians (ACP) in 2011:[28][29]
    • "ACP recommends assessment of the risk for thromboembolism and bleeding in medical (including stroke) patients prior to initiation of prophylaxis of venous thromboembolism (Grade: strong recommendation, moderate-quality evidence)."
    • "ACP recommends pharmacologic prophylaxis with heparin or a related drug for venous thromboembolism in medical (including stroke) patients unless the assessed risk for bleeding outweighs the likely benefits (Grade: strong recommendation, moderate-quality evidence)."
    • "ACP recommends against the use of mechanical prophylaxis with graduated compression stockings for prevention of venous thromboembolism (Grade: strong recommendation, moderate-quality evidence)."
    • "ACP does not support the application of performance measures in medical (including stroke) patients that promotes universal venous thromboembolism prophylaxis regardless of risk."
  • American College of Chest Physicians (ACCP) in 2011:[30]
  • "For acutely ill hospitalized medical patients at increased risk of thrombosis, we recommend anticoagulant thromboprophylaxis with low-molecular-weight heparin (LMWH), low-dose unfractionated heparin (LDUH) bid, LDUH tid, or fondaparinux (Grade 1B) and suggest against extending the duration of thromboprophylaxis beyond the period of patient immobilization or acute hospital stay (Grade 2B).
  • "For acutely ill hospitalized medical patients at low risk of thrombosis, we recommend against the use of pharmacologic prophylaxis or mechanical prophylaxis (Grade 1B)."
  • "For acutely ill hospitalized medical patients at increased risk of thrombosis who are bleeding or are at high risk for major bleeding, we suggest mechanical thromboprophylaxis with graduated compression stockings (GCS) (Grade 2C) or intermittent pneumatic compression (IPC) (Grade 2C)."
  • "For critically ill patients, we suggest using LMWH or LDUH thromboprophylaxis (Grade 2C). For critically ill patients who are bleeding or are at high risk for major bleeding, we suggest mechanical thromboprophylaxis with GCS and/or IPC at least until the bleeding risk decreases (Grade 2C)."
  • "In outpatients with cancer who have no additional risk factors for VTE we suggest against routine prophylaxis with LMWH or LDUH (Grade 2B) and recommend against the prophylactic use of vitamin K antagonists (Grade 1B)."

Extending anticoagulation for an addition 28 days may benefit patients who are "women, patients older than 75 years, and those with level 1 mobility. Level I mobility is being bed rest or sedentary without bathroom privileges."[31]

Compression devices that are mobile may be effective.[32]

Rosuvastatin, a hydroxymethylglutaryl-coenzyme A reductase inhibitor (statin), may reduce embolism and thrombosis according to the Jupiter randomized controlled trial.[33]

Studies on implementing guidelines are available.[2][34]

Oncology patients

According to a clinical practice guideline by the American Society of Clinical Oncology, "all hospitalized cancer patients should be considered for VTE prophylaxis with anticoagulants in the absence of bleeding or other contraindications."[35]

For oncology patients who have had a thrombus, consider lifelong prophylaxis with enoxaparin 1.5 mg/kg per day.[36]

Surgery Patients

The risk of DVT after surgery may persist up to 12 weeks.[37]

Hip or knee surgery

Clinical practice guidelines by the American College of Chest Physicians[38] and the American Academy of Orthopaedic Surgeons[39] address prevention. Unfortunately, these guidelines have substantial conflict.[40]

Low molecular weight heparins may provide better anticoagulation for prophylaxis of deep venous thrombosis among orthopedic patients than direct thrombin inhibitors because the latter may increase complications.[41] However, if anticoagulation is started before surgery, direct thrombin inhibitors may be more effective.

Extending anticoagulation (25-35 days) with low molecular weight heparin, such as enoxaparin 30 to 40 mg subcutaneously once daily can reduce symptomatic DVT in one of every 45 patients treated and can reduce any (symptomatic or assymptomatic) DVT in one of every 8 patients treated.[42] As these studies were short term, it is likely that some patients with asymptomatic DVT progress to chronic venous insufficiency.

Even knee arthroscopic meniscectomy may benefit from low molecular weight heparin.[43]

Factor Xa inhibitors

Spinal surgery

Clinical practice guidelines by the American College of Chest Physicians address this topic.[48]

Travelers

Travel may[49] or may not[50] lead to DVT according to meta-analyses.

Trials suggests that wearing compression socks while traveling also reduces the incidence of thrombosis in people on long haul flights. A randomized study in 2001 compared two sets of long haul airline passengers, one set wore travel compression hosiery the others did not. The passengers were all scanned and blood tested to check for the incidence of DVT. The results showed that asymptomatic DVT occurred in 10% of the passengers who did not wear compression socks. The group wearing compression had no DVTs. The authors concluded that wearing elastic compression hosiery reduces the incidence of DVT in long haul airline passengers.[51].

Therapy

Treatment options have been reviewed.[52]

Regarding the duration of anticoagulation, see embolism and thrombosis: treatment.
  • Elastic compression stockings have been strongly encouraged.[56][58] The stockings in almost all trials were stronger than routine anti-embolism stockings and created either 20-30 mm Hg or 30-40 mm Hg. Most trials used knee-high stockings. A meta-analysis of randomized controlled trials by the Cochrane Collaboration showed reduced incidence of post-phlebitic syndrome.[59] The number needed to treat is quite potent at 4 to 5 patients need to prevent one case of post-phlebitic syndrome.[60] However, a more recent trial found that prophylactic use of compression stockings after deep venous thrombosis may not prevent venous insufficiency.[61]Compression stocking can cause local complications.[62]
  • Inferior vena cava filter also referred to as a Greenfield filter, reduces pulmonary embolism[63] and is an option for patients with an absolute contraindication to anticoagulant treatment (e.g., cerebral hemorrhage) or those rare patients who have objectively documented recurrent PEs while on anticoagulation. However these filters are themselves potential foci of thrombosis,[64] IVC filters are viewed as a temporizing measure for preventing life-threatening pulmonary embolism.
  • Hospitalization should be considered in patients with more than two of the following risk factors as these patients may have more risk of complications during treatment[65]:
    • bilateral DVT, renal insufficiency, body weight <70 kg, recent immobility, chronic heart failure, and cancer

Oncology patients

A clinical practice guideline published in 2004 by the American College of Chest Physicians states:[66]

"for patients with DVT and cancer, we recommend LMWH for the first 3 to 6 months of long-term anticoagulant therapy (Grade 1A). For these patients, we recommend anticoagulant therapy indefinitely or until the cancer is resolved".

A clinical practice guideline published in 2007 by the American Society of Clinical Oncology states:[35]

"1) low molecular weight heparin LMWH is the preferred approach for the initial 5 to 10 days of anticoagulant treatment of the cancer patient with established VTE, 2) LMWH given for at least 6 months is also the preferred approach for long-term anticoagulant therapy. Vitamin K antagonists with a targeted INR of 2 to 3 are acceptable for long-term therapy when LMWH is not available. 3) After 6 months, indefinite anticoagulant therapy should be considered for selected patients with active cancer, such as those with metastatic disease and those receiving chemotherapy. This recommendation is based on Panel consensus in the absence of clinical trials data."

Determining when to stop treatment

D-Dimer

An abnormal D-dimer level at the end of treatment might signal the need for continued anticoagulation with warfarin among patients with embolism and thrombosis such as a first unprovoked pulmonary embolism.[67] If the D-dimer is abnormal, anticoaguation should be continued, if the D-dimer is normal, the duration of treatment is uncertain.[68] In an observation study that collected the D-dimer before stopping anticoagulation, the D-dimer was not as predictive.[69]

Ultrasonography

Ultrasonography, using the following protocol may[70] or may not[71] help determine when to stop anticoaguation[70]:

"If veins had not recanalized, we invited patients to have further ultrasonography after 3 and 9 months in patients with secondary DVT and after 3, 9, 15, and 21 months in those with unprovoked DVT. Anticoagulation was discontinued when the veins had recanalized, along with further ultrasonography"

Prognosis

Reducing the risk of recurrence after an unprovoked deep venous thrombosis.[72] [73] [67] [74] [75]
  Treatment or test Risk if treated or test result is favorable Risk if not treated or test result is unfavorable Comments
Randomized controlled trial[72] Aspirin 100 mg daily for 2 years 6% per year 11.2% per year 0.5% major bleeding
Randomized controlled trial[73] Rivaroxaban for 6-12 months 1% over 6-12 months 7% over 6-12 months 0.7% major bleeding
Systematic review of a diagnostic test[67][75] Normal d-dimer 4% per year 9% per year
Systematic review of a diagnostic test[74] Recanalization of veins (no residual vein obstruction or RVO) Insignificant difference

Postthrombotic syndrome

Postthrombotic syndrome along with postphlebitic syndrome are forms of venous insufficiency. Postthrombotic syndrome is a "condition caused by one or more episodes of deep vein thrombosis, usually the blot clots are lodged in the legs. Clinical features include edema; pain; aching; heaviness; and muscle cramp in the leg. When severe leg swelling leads to skin breakdown, it is called venous stasis ulcer."[76][77]

The incidence of postthrombotic syndrome is 76.1 per 100,000 person-years.[78] Regarding the etiology of the postthrombotic syndrome, about 40% are from prior DVT[79] although only 25% of patients report a prior diagnosis of DVT[78]. This suggests nearly half of the prior DVTs were undiagnosed.

Natural history of a diagnosed DVT

The natural history of a diagnosed DVT is as follows. After two years, the probability of postthrombotic syndrome is:[80]

  • No postthrombotic syndrome 60%
  • Mild postthrombotic syndrome 26%
  • Moderate postthrombotic syndrome 11%
  • Severe postthrombotic syndrome 3%

Risk factors include:

  • Prior ipsilateral DVT
  • Obesity
  • Female gender
  • Older age

After 5 to 10 years: One cohort reported 28% incidence (using a definition that required more significant symptoms)at five years.[81]

Among patients 6 to 8 years after a DVT, two studies provide risks:

  • "42% reported pain, swelling, or discoloration."[82]
  • A second study found 70% risk at 8 years.[64]

After 10 to 20 years: Although after 20 years, only 26.8% of patients will have sought medical care and be diagnosed with late complications of DVT[83], when patients are actively studied 10-20 years after their initial thrombosis, 80% have some signs of postthrombotic syndrome.[84]

Recurrent DVT

Risk factors for recurrence if anticoagulation is stopped are:[85]

  • post-thrombotic symptoms such as "hyperpigmentation, edema or redness of either leg"
  • D-dimer > or = 250 microg/L while taking warfarin> Other studies suggest the D-dimer should be checked after stopping warfarin.
  • body mass index > or = 30 kg/m(2)
  • age > or = 65 years
  • male gender

References

  1. ↑ 1.0 1.1 1.2 Woller SC, Stevens SM, Jones JP, Lloyd JF, Evans RS, Aston VT et al. (2011). "Derivation and validation of a simple model to identify venous thromboembolism risk in medical patients.". Am J Med 124 (10): 947-954.e2. DOI:10.1016/j.amjmed.2011.06.004. PMID 21962315. Research Blogging.
  2. ↑ 2.0 2.1 2.2 2.3 Kucher N, Koo S, Quiroz R, Cooper JM, Paterno MD, Soukonnikov B et al. (2005). "Electronic alerts to prevent venous thromboembolism among hospitalized patients.". N Engl J Med 352 (10): 969-77. DOI:10.1056/NEJMoa041533. PMID 15758007. Research Blogging.
  3. ↑ Tsai A, Cushman M, Rosamond W, Heckbert S, Polak J, Folsom A (2002). "Cardiovascular risk factors and venous thromboembolism incidence: the longitudinal investigation of thromboembolism etiology.". Arch Intern Med 162 (10): 1182-9. PMID 12020191.
  4. ↑ Trujillo-Santos J, Prandoni P, Rivron-Guillot K, et al (2008). "Clinical outcome in patients with venous thromboembolism and hidden cancer: findings from the RIETE Registry". J Thromb Haemost 6 (2): 251–255. DOI:10.1111/j.1538-7836.2007.02837.x. PMID 18021305. Research Blogging.
  5. ↑ Larsen TB, Sørensen HT, Skytthe A, Johnsen SP, Vaupel JW, Christensen K (2003). "Major genetic susceptibility for venous thromboembolism in men: a study of Danish twins". Epidemiology 14 (3): 328-32. PMID 12859034. [e]
  6. ↑ Bezemer, I. D., Bare, L. A., Doggen, C. J. M., Arellano, A. R., Tong, C., Rowland, C. M., et al. (2008). Gene variants associated with deep vein thrombosis, JAMA, 299(11), 1306-1314. DOI:10.1001/jama.299.11.1306.
  7. ↑ 7.0 7.1 Geersing GJ, Zuithoff NP, Kearon C, Anderson DR, Ten Cate-Hoek AJ, Elf JL et al. (2014). "Exclusion of deep vein thrombosis using the Wells rule in clinically important subgroups: individual patient data meta-analysis.". BMJ 348: g1340. DOI:10.1136/bmj.g1340. PMID 24615063. PMC PMC3948465. Research Blogging.
  8. ↑ Qaseem A, Snow V, Barry P, et al (2007). "Current diagnosis of venous thromboembolism in primary care: a clinical practice guideline from the American Academy of Family Physicians and the American College of Physicians". Ann. Intern. Med. 146 (6): 454–8. PMID 17371890. [e]
  9. ↑ 9.0 9.1 Wells PS, Hirsh J, Anderson DR, et al (1995). "Accuracy of clinical assessment of deep-vein thrombosis". Lancet 345 (8961): 1326–30. PMID 7752753. [e]
  10. ↑ 10.0 10.1 Wells PS, Anderson DR, Rodger M, et al (2003). "Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis". N. Engl. J. Med. 349 (13): 1227–35. DOI:10.1056/NEJMoa023153. PMID 14507948. Research Blogging.
  11. ↑ 11.0 11.1 11.2 Scarvelis D, Wells PS (2006). "Diagnosis and treatment of deep-vein thrombosis". CMAJ 175 (9): 1087–92. DOI:10.1503/cmaj.060366. PMID 17060659. Research Blogging.
  12. ↑ 12.0 12.1 Linkins LA, Bates SM, Lang E, Kahn SR, Douketis JD, Julian J et al. (2013). "Selective d-Dimer Testing for Diagnosis of a First Suspected Episode of Deep Venous Thrombosis: A Randomized Trial.". Ann Intern Med 158 (2): 93-100. DOI:10.7326/0003-4819-158-2-201301150-00003. PMID 23318311. Research Blogging.
  13. ↑ 13.0 13.1 van der Velde EF, Toll DB, Ten Cate-Hoek AJ, Oudega R, Stoffers HE, Bossuyt PM et al. (2011). "Comparing the diagnostic performance of 2 clinical decision rules to rule out deep vein thrombosis in primary care patients.". Ann Fam Med 9 (1): 31-6. DOI:10.1370/afm.1198. PMID 21242558. Research Blogging.
  14. ↑ Wells PS, Anderson DR, Bormanis J, et al (1997). "Value of assessment of pretest probability of deep-vein thrombosis in clinical management". Lancet 350 (9094): 1795–8. DOI:10.1016/S0140-6736(97)08140-3. PMID 9428249. Research Blogging.
  15. ↑ 15.0 15.1 Oudega R, Hoes AW, Moons KG (2005). "The Wells rule does not adequately rule out deep venous thrombosis in primary care patients". Ann. Intern. Med. 143 (2): 100–7. PMID 16027451. [e]
  16. ↑ Toll, DB et al. 2008. “A new diagnostic rule for deep vein thrombosis: safety and efficiency in clinically relevant subgroups.” Fam. Pract. 2008. http://fampra.oxfordjournals.org/cgi/content/full/cmm075v1
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  18. ↑ Kleinjan A, Di Nisio M, Beyer-Westendorf J, Camporese G, Cosmi B, Ghirarduzzi A et al. (2014). "Safety and Feasibility of a Diagnostic Algorithm Combining Clinical Probability, d-Dimer Testing, and Ultrasonography for Suspected Upper Extremity Deep Venous Thrombosis: A Prospective Management Study.". Ann Intern Med 160 (7): 451-7. DOI:10.7326/M13-2056. PMID 24687068. Research Blogging.
  19. ↑ Lensing AW, Prandoni P, Brandjes D, Huisman PM, Vigo M, Tomasella G et al. (1989). "Detection of deep-vein thrombosis by real-time B-mode ultrasonography.". N Engl J Med 320 (6): 342-5. PMID 2643771.
  20. ↑ White RH, McGahan JP, Daschbach MM, Hartling RP (1989). "Diagnosis of deep-vein thrombosis using duplex ultrasound.". Ann Intern Med 111 (4): 297-304. PMID 2667418.
  21. ↑ 21.0 21.1 Lewis BD, James EM, Welch TJ, Joyce JW, Hallett JW, Weaver AL (1994). "Diagnosis of acute deep venous thrombosis of the lower extremities: prospective evaluation of color Doppler flow imaging versus venography.". Radiology 192 (3): 651-5. PMID 8058929.
  22. ↑ Johnson SA, Stevens SM, Woller SC, Lake E, Donadini M, Cheng J et al. (2010). "Risk of deep vein thrombosis following a single negative whole-leg compression ultrasound: a systematic review and meta-analysis.". JAMA 303 (5): 438-45. DOI:10.1001/jama.2010.43. PMID 20124539. Research Blogging.
  23. ↑ Bernardi E, Camporese G, Büller HR, et al (October 2008). "Serial 2-point ultrasonography plus D-dimer vs whole-leg color-coded Doppler ultrasonography for diagnosing suspected symptomatic deep vein thrombosis: a randomized controlled trial". JAMA : the journal of the American Medical Association 300 (14): 1653–9. DOI:10.1001/jama.300.14.1653. PMID 18840838. Research Blogging.
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  26. ↑ Wikipedia has an article about the plantaris muscle.
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  44. ↑ Eriksson BI, Bauer KA, Lassen MR, Turpie AG (November 2001). "Fondaparinux compared with enoxaparin for the prevention of venous thromboembolism after hip-fracture surgery". The New England journal of medicine 345 (18): 1298–304. PMID 11794148. [e]
  45. ↑ Lassen MR, Ageno W, Borris LC, et al (June 2008). "Rivaroxaban versus enoxaparin for thromboprophylaxis after total knee arthroplasty". The New England journal of medicine 358 (26): 2776–86. DOI:10.1056/NEJMoa076016. PMID 18579812. Research Blogging.
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  47. ↑ Kakkar AK, Brenner B, Dahl OE, et al (July 2008). "Extended duration rivaroxaban versus short-term enoxaparin for the prevention of venous thromboembolism after total hip arthroplasty: a double-blind, randomised controlled trial". Lancet 372 (9632): 31–9. DOI:10.1016/S0140-6736(08)60880-6. PMID 18582928. Research Blogging. (this trial compared rivaroxaban to short-term enoxaparin
  48. ↑ Gould MK, Garcia DA, Wren SM, Karanicolas PJ, Arcelus JI, Heit JA et al. (2012). "Prevention of VTE in nonorthopedic surgical patients: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.". Chest 141 (2 Suppl): e227S-77S. DOI:10.1378/chest.11-2297. PMID 22315263. PMC PMC3278061. Research Blogging.
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  54. ↑ Enden, Tone; Ylva Haig, Nils-Einar Kløw, Carl-Erik Slagsvold, Leiv Sandvik, Waleed Ghanima, Geir Hafsahl, Pål Andre Holme, Lars Olaf Holmen, Anne Mette Njaastad, Gunnar Sandbæk, Per Morten Sandset (2011-12). "Long-term outcome after additional catheter-directed thrombolysis versus standard treatment for acute iliofemoral deep vein thrombosis (the CaVenT study): a randomised controlled trial". The Lancet. DOI:10.1016/S0140-6736(11)61753-4. ISSN 01406736. Retrieved on 2011-12-15. Research Blogging.
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  57. ↑ Buller HR, Lensing AW, Prins MH, et al (September 2008). "A dose-ranging study evaluating once-daily oral administration of the factor Xa inhibitor rivaroxaban in the treatment of patients with acute symptomatic deep vein thrombosis: the Einstein-DVT Dose-Ranging Study". Blood 112 (6): 2242–7. DOI:10.1182/blood-2008-05-160143. PMID 18621928. Research Blogging.
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  85. ↑ Rodger MA, Kahn SR, Wells PS, et al (August 2008). "Identifying unprovoked thromboembolism patients at low risk for recurrence who can discontinue anticoagulant therapy". CMAJ 179 (5): 417–26. DOI:10.1503/cmaj.080493. PMID 18725614. PMC 2518177. Research Blogging.

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