Four days after undergoing subtotal gastrectomy for stomach cancer, a 58-year-old woman complains of right leg and thigh pain, swelling and redness, and has tenderness on examination. The diagnosis of deep vein thrombosis is entertained. What is the initial test to establish the diagnosis?

The most accurate method of confirming the diagnosis of venous thrombosis is the injection of contrast material to visualize the venous system (venography). However, this method is invasive and time-consuming and must be done in the radiology suite. Venous duplex ultrasound is noninvasive, can be done bedside, and has a sensitivity and specificity of 96 and 100%, respectively. The other methods listed are used less often in certain selected patients.