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DVT | Advanced

Salim Rezaie, MD and Mizuho Morrison, DO

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Regardless of your clinical setting, DVT’s are a common entity that we need to be very comfortable working up and treating. And though on the surface the workup and Tx is seemingly straightforward...the truth is there are some nuances and special cases that aren’t completely intuitive...Mizuho chats with Salim Rezaie about this topic to reveal some practice changing pearls.



  • DVT can be excluded clinically in patients with a low Well’s Score.

  • Patients with medium to high risk score require diagnostic testing to exclude DVT.

  • A negative venous duplex plus d-dimer excludes DVT with excellent sensitivity. 

  • Patients with a positive d-dimer, but negative ultrasound should have a repeat US in 1 week.

  • Proximal/iliofemoral DVT and/or phlegmasia are high. Anticoagulation alone is not appropriate and they should be referred to an ED with vascular surgery/IR capabilities.

  • Patients with DVT and active cancer should be treated with subQ LMWH BID. 


  • DVT is a “can’t miss” diagnosis in patients presenting with leg pain and/or swelling, however, only ~25% of patients presenting with unilateral lower leg symptoms will have a DVT.

    • 80% of pulmonary emboli will originate from a lower extremity DVT.


  • Familiarity with which veins comprise the deep venous system of the legs is important because treatment of DVTs differs significantly from that of superficial thrombophlebitis.

    • Additionally, it’s worthwhile to distinguish between proximal and distal deep veins because management can often change based on the location of the DVT as well. 

Proximal Deep Veins:

  • The superficial femoral vein, despite the name, is actually a large, proximal, DEEP vein.

Distal Deep Veins:


  • Beginning with the popliteal vein, which trifurcates into the anterior tibial, posterior tibial, and peroneal veins, and below is considered the distal deep venous system. 


  • The risk factors for DVT are summarized in “Virchow’s Triad.”

    • Vessel problems/endothelial injury - e.g. recent trauma, recent surgery, central lines

    • Blood problems - e.g. metastatic cancer, hypercoagulable disorders, autoimmune disease, pregnancy/estrogen use

    • Flow/stasis problems - e.g. immobilization/inactivity, obstruction (from masses, uterus during pregnancy, etc.)

      • Many patients with DVT will have a combination of these risk factors.

  • DVT should be suspected when there is some combination unilateral leg pain, swelling, warmth, redness and a risk factor for DVT.

    • If swelling/symptoms are bilateral, systemic disease (e.g heart failure or cirrhosis) is much more likely than DVT (or cellulitis).

  • Some form of diagnostic testing is essential for ruling in and ruling out DVT.

    • None of the eponymous signs discussed in textbooks, such as Homan’s sign, are sufficiently sensitive or specific to be clinically useful in the diagnosis of DVT.

  • The diagnostic test of choice will depend on the patient’s pre-test probability of having DVT.

    • Pre-test probability can be determined with a risk stratification tool (e.g. Well’s Criteria).


  • DVT can be excluded clinically with reasonable certainty in patients with a “low risk” Well’s Score.

    • Well’s Score for DVT has many criteria and should be calculated using a quick clinical reference tool such as MDCalc.

  • “Moderate” and “high” risk patients (ie: patients with ANY risk factor where there is not a more likely diagnosis than DVT) can be approached similarly.  

    • Duplex ultrasound is the diagnostic test of choice for moderate-high risk patients. 

      • If the ultrasound is positive, then begin treatment for DVT.

      • If the ultrasound is negative, Dr. Rezaie recommends getting a d-dimer (ensure that your lab uses a “high sensitivity assay”) because ultrasound is not sufficiently sensitive to rule out DVT when there is a high pre-test probability. 

        • If the ultrasound AND d-dimer are negative, DVT has been excluded.

        • If the ultrasound is negative, BUT the d-dimer is positive, a repeat ultrasound is recommended in 1 week because a small, distal clot can be missed. 

          • These small distal DVTs can progress in ~30% of cases. 

          • Treatment with aspirin, for both analgesia and antiplatelet effect, is recommended while awaiting repeat ultrasound. 

  • Neither D-dimer nor duplex ultrasound are sufficiently sensitive to rule out DVT if the pretest probability of clot is high. 


  • N.B. - Ordering a d-dimer simultaneously with ultrasound can save time after deciding to work a patient up for suspected DVT because, ultimately, both tests may be necessary. 


Distal DVT:

  • Treatment of distal/calf vein DVTs is controversial because there has only been one large study of this entity (the CACTUS trial), which showed ambiguous results with respect to risks vs. benefits of  anticoagulation. 

  • For distal DVTs of the calf veins, anticoagulation should be favored if:

    • D-dimer is markedly elevated because this suggests active thrombosis and risk for clot propagation.

    • Clot is larger than 5 cm in length.  

    • Vein diameter is >7mm.

    • The patient has history of active malignancy or prior VTE.

    • For patients with distal calf vein DVTs who you elect NOT to anticoagulate, begin 325mg of aspirin daily and repeat a venous duplex of the leg in ~14 days.

High Risk DVTs: 

  • When the entire leg is swollen and discolored, consider the possibility of phlegmasia alba dolens or phlegmasia cerulea dolens (ie: conditions where the entire deep venous system has clotted and there is no venous return).

    • Treatment for phlegmasia/completely obstructing DVT is NOT anticoagulation alone, but rather urgent procedural intervention.

      • Patients should be immediately referred to ED/hospital with both vascular surgery and interventional radiology capabilities. 

  • Very proximal DVTs (i.e. Iliofemoral) are high risk for causing massive pulmonary embolism and subsequent cardiac arrest. 

    • Patients with iliofemoral DVT generally will benefit from admission and close monitoring. 

Anticoagulation for Non-High Risk DVT:

  • Treatment consists of anticoagulation with either some form of heparin, bridging to warfarin or a direct oral anticoagulant (DOAC), such as apixaban. 

    • Both strategies are equally effective, have roughly the same risk of bleed, and are appropriate for non-cancer related DVT.

      • Consider the patient’s insurance coverage and lifestyle and involve the patient in the decision of whether warfarin or a DOAC is more appropriate. 

        • DOACs are much more expensive, but do not require INR monitoring. 

    • For cancer related DVT, subQ low-molecular weight heparin BID is recommended because of significantly lower risk of recurrence. 



  1. Di Nisio M et al. Deep Vein Thrombosis and Pulmonary Embolism. Lancet 2016; 388 (10063): 3060 - 3073. PMID: 27375038

  2. Hirsh J et al. Management of Deep Vein Thrombosis and Pulmonary Embolism.  A Statement for Healthcare Professionals. Council on Thrombosis (in consultation with the Council on Cardiovascular Radiology), American Heart Association. Circulation 1996; 93 (12): 2212 - 45. PMID: 8925592

  3. Simel DL et al. The Rational Clinical Examination: Evidence-Based Clinical Diagnosis. JAMAEvidence 2009. (

  4. Wells PS et al. Accuracy of clinical Assessment of Deep-Vein Thrombosis. Lancet 1995; 345 (8961): 1326 - 30. PMID: 7752753

  5. Adams D et al. Clinical Utility of an Age-Adjusted D-Dimer in the Diagnosis of Venous Thromboembolism. Ann emerg Med 2014; 64 (3): 232 - 4. PMID: 24439717

  6. Kearon C et al. Antithrombotic Therapy for VTE Disease CHEST Guideline and Expert Panel Report. Chest 2016; 149 (2): 315 - 352. PMID: 26867832

  7. Caironi P, Tognoni G, et al. ALBIOS Study Investigators. Albumin replacement in patients with severe sepsis or septic shock. N Engl J Med 2014; 370:1412-21.

Mike W., MD -

Listener questio:
66 y/o female, fall on ice.. TPF type 3, s/p ORIF and clavicle fx, ORziF same. 3 days later marked edema and pain from axillary to finger tips.
Would u still order ad dimer?
US positive, huge DVT . But if not. Would the same principle apply?
Interesting. I always always worry abt alt DX, with arm, but this was fairly classic.

Answer from Salim Rezaie: Short answer….evidence for UE DVT is much more sparse, however the more proximal veins are still not insignificant. I would still do D-Dimer + US and have a follow up US in 1 week if D-Dimer positive. My two cents…no strong evidence either way.

Ian L., Dr -

Would Anticoagulation decrease swelling and discomfort and lessen a chronic thrombosis chronic swelling syndrome.

Mike W., MD -

Reply from Salim:
Anticoagulation helps decrease progression of thrombosis and lets the body get rid of thrombosis that is present. As thrombosis dissipates so does swelling and pain. This should also be balanced with bleeding risk.

Dianna M. -

Regarding the workup of DVT / obtaining ddimer for negative US, is this evidence based or is this Dr. Rezaie's practice preference / pattern? Thank you! I was speaking to a colleague about this topic and he was concerned this was not evidence based.

Mizuho M., DO -


Great question. The data is not robust on this. However based on the evidence we do have…it is not just simply Dr.Rezaie’s practice…I refer you to look at recommendations by AHA which were referenced in the notes section of this segment.

Hirsh J et al. Management of Deep Vein Thrombosis and Pulmonary Embolism. A Statement for Healthcare Professionals. Council on Thrombosis (in consultation with the Council on Cardiovascular Radiology), American Heart Association. Circulation 1996; 93 (12): 2212 - 45. PMID: 8925592

Under the section "Performance of Testing” it will tell you that venography is actually Gold Standard. However this is an invasive procedure and impractical. Thus doppler US is preferred imaging modality. However US is not without its errors. Hence AHA states the following:

"There is evidence from diagnostic studies using serial noninvasive testing in patients with symptoms of DVT that calf vein thrombi are not dangerous, provided that they remain confined to calf veins.33585111 However, calf vein thrombi can extend and do so in ≈30% of cases.74 Because only ≈5% of patients with symptoms of DVT have calf vein thrombosis (Fig 3),78 it is safe to exclude clinically important venous thrombosis if the venous ultrasonography is negative at presentation in patients who have low pretest clinical probability, because the negative predictive value of a negative venous ultrasound is more than 99%.80 In patients at moderate or high clinical probability, however, it would be prudent to repeat the test once after 5 to 7 days to detect the small percentage of patients with calf vein thrombosis that extends (Fig 4).”

Later in the segment we talk about placing these high clinical probability patients on ASA while we wait for repeat US…this was stated as Dr.Rezaie’s personal practice only, as there is insufficient evidence anywhere unfortunately, hence this was noted to be HIS personal practice alone.

I hope that helps clarify things. Thanks for listening. Mizuho

Mizuho M., DO -

p.s. highly recommend you pull that paper link above and read the entire AHA document...pretty interesting. Good luck!

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