Sonography and venography of the lower extremities for diagnosing deep vein thrombosis in symptomatic patients.

The purpose of this study was to investigate the efficacy of sonography and the frequency of indeterminate sonographic examinations in the evaluation of patients with suspected lower extremity deep vein thrombosis (DVT). We prospectively evaluated 136 symptomatic patients (157 extremities) with suspected DVT using sonography and contrast-enhanced venography (n=106 patients, 115 extremities). Using venography as the reference standard for diagnosing DVT, the sensitivity and specificity of sonography was 92.8% and 98%, respectively, yielding an accuracy of 96.8%. The frequency of indeterminate examinations for calf DVT was 32.4%. One (0.7%) fatal pulmonary embolus occurred in our patients. The pulmonary embolism (PE) rate was 1.6% after lower extremity sonography with negative results. Sonography is highly accurate in detecting lower extremity DVT in symptomatic patients. Because of the high frequency of indeterminate studies in the calf and the associated possible risk of pulmonary emboli, we urge radiologists exercise additional caution when evaluating symptomatic patients with clinically suspected lower extremity DVT.