A 23-year-old woman four days after ACL repair presents with unilateral leg swelling and warmth. What is the initial diagnostic study of choice for the suspected deep vein thrombosis?

• A. Venous duplex ultrasound
• B. Plain radiography
• C. Computed tomography angiography
• D. Ventilation-perfusion scan

Answer: (A)

When you suspect a deep vein thrombosis, the first test to get is venous duplex ultrasound. This test is noninvasive, readily available, and uses compression with Doppler to visualize the veins in the leg. If a vein cannot be compressed, that usually means a clot is present. It directly assesses the major sites where DVT typically occurs (femoral, popliteal) and has high sensitivity and specificity for proximal DVT, making it the most effective initial diagnostic tool in this setting.

Other tests shown are not designed to diagnose DVT. Plain radiographs don’t visualize the venous system. Computed tomography angiography is used mainly to evaluate pulmonary embolism or arterial pathology, and involves radiation and contrast; it’s not the initial test for DVT. Ventilation-perfusion scans are also used for PE, not for diagnosing DVT. In this postoperative, unilateral leg swelling scenario, venous duplex ultrasound is the appropriate first choice.