Ultrasonography frequently is performed to evaluate patients with suspected deep venous thrombosis (DVT) of the leg. Simplified compression ultrasonography has high accuracy for symptomatic proximal venous thrombosis but can miss thrombosis of the distal calf veins. A repeat simplified compression ultrasonography is necessary within five to seven days to look for proximal thrombus propagation. Comprehensive duplex ultrasonography examines the deep veins within the entire leg down to the malleolus, thus potentially obviating routine repeat scanning. Stevens and associates performed a prospective cohort study of patients with a suspected first episode of DVT who had a negative comprehensive leg duplex ultrasonogram.

The researchers examined the rate of venous thromboembolism in these patients after withholding anticoagulant therapy for three months. Exclusion criteria included previous DVT, pregnancy, and patients receiving long-term anticoagulation therapy for another reason. Comprehensive ultrasonography was performed by registered vascular technologists and interpreted by a vascular surgeon. If a single, noncompressible segment was identified, the study was reported as positive, and the patient was diagnosed with DVT. If the results of all imaged venous segments were negative, anticoagulation was withheld without consideration of symptoms or clinical signs.

Patients in the negative cohort were interviewed about multiple aspects of their health at least three months after enrollment in the study. The primary outcome measure was venous thromboembolism diagnosed by objective testing, including death caused by a venous thromboembolism.

During the three-month period, symptoms of recurrent venous thromboembolism occurred in 22 of the 375 patients in the negative cohort, with three patients actually having objective evidence of symptomatic venous thrombosis (0.80 percent). Among the other 19 patients, four had suspected pulmonary embolism that was not confirmed by objective testing. Six patients in the negative cohort died in the three-month follow-up period; none of the deaths were caused by venous thromboembolism.

The authors conclude that although comprehensive duplex ultrasonography takes more time to perform than simplified compression ultrasonogaphy, the advantage of requiring only a single examination is significant. They state that it is safe to withhold anticoagulation from patients with suspected symptomatic DVT who have a negative comprehensive duplex sonogram, repeatedly negative simplified compression ultrasonograms, or one negative simplified duplex ultrasonogram and normal results on a whole blood D-dimer test. When comprehensive ultrasonography reveals thrombosis isolated to the calf vein, anticoagulation can be withheld if ultrasonography is repeated to monitor extension of these thrombi into proximal deep veins. The authors add that these results may not apply to patients who are pregnant or if factors prevent visualization of the deep venous system of the calf.

In an accompanying editorial, El Kheir and Büller confirm the value of the single comprehensive ultrasonogram approach and recommend further testing of this procedure with good pretest clinical probability analysis or D-dimer testing to find the optimal algorithm to evaluate patients for symptomatic DVT.