What is the workup for deep vein thrombosis (DVT) of the lower extremities?

From the Guidelines

The workup for thrombosis of the lower extremities should begin with a thorough clinical assessment, followed by diagnostic testing with US duplex Doppler lower extremity as the recommended initial imaging examination, as stated in the ACR Appropriateness Criteria 1. When thrombosis is suspected, a D-dimer blood test is typically ordered first; if elevated, imaging studies are warranted. The following are key points to consider in the workup:

• Clinical assessment: A detailed history and physical examination are essential in evaluating patients with suspected lower extremity deep vein thrombosis (DVT) 1.
• Diagnostic testing: US duplex Doppler lower extremity is the preferred initial imaging modality due to its non-invasive nature, high sensitivity, and specificity for proximal DVT 1.
• Imaging modalities: If ultrasound results are inconclusive but clinical suspicion remains high, contrast venography, CT venography, or MR venography may be performed 1.
• Anticoagulation therapy: Once DVT is confirmed, anticoagulation therapy should be initiated promptly, typically with low molecular weight heparin or fondaparinux, overlapping with warfarin for at least 5 days until therapeutic INR is achieved 1.
• Treatment duration: Treatment duration depends on risk factors, with 3 months for provoked DVT and longer for unprovoked or recurrent events 1.
• Additional workup: Screening for underlying conditions such as malignancy, thrombophilia, or autoimmune disorders should be considered, particularly in patients with unprovoked, recurrent, or unusual-site thrombosis 1.

From the Research

Diagnostic Approach

• The diagnostic work-up for thrombosis of the lower extremities involves assessing pretest probability, followed by D-dimer testing and imaging with venous ultrasonography 2, 3, 4.
• A normal D-dimer level (less than 500 ng/mL) can exclude acute venous thromboembolism (VTE) when combined with a low pretest probability (Wells DVT score ≤1) 2.
• The sensitivity and specificity of proximal compression ultrasonography for diagnosing deep vein thrombosis (DVT) are 90.1% and 98.5%, respectively 5.
• Whole-leg ultrasonography has a sensitivity of 94.0% and specificity of 97.3% for diagnosing DVT 5.

Risk Factors and Treatment

• Risk factors for VTE include older age, malignancy, inflammatory disorders, and inherited thrombophilia 2.
• The treatment of VTE involves anticoagulation therapy, with direct oral anticoagulants (such as rivaroxaban and apixaban) being noninferior to warfarin in terms of efficacy and associated with lower rates of bleeding 2, 3, 4.
• Catheter-directed fibrinolysis with or without mechanical thrombectomy may be appropriate for patients with iliofemoral obstruction, severe symptoms, and a low risk of bleeding 2.
• Compression therapy is used to prevent postthrombotic syndrome, which occurs in 25% to 50% of patients 3 to 6 months after DVT diagnosis 2, 3.

Special Considerations

• In obese patients, standard doses of rivaroxaban and apixaban are appropriate 3.
• In cancer-associated thromboembolism, the use of low molecular weight heparin (LMWH) or factor Xa inhibitors is recommended, depending on the type of cancer and expected drug-drug interactions with anticancer treatment 3.
• The duration of anticoagulation therapy depends on the risk of VTE recurrence and bleeding, with extended treatment considered for patients with unprovoked or persistent risk factors 3, 4.