Diagnosis of femoropopliteal venous thrombosis: comparison of duplex sonography and plethysmography.

Duplex sonography and impedance plethysmography were correlated with contrast venography to compare the sensitivity, specificity, and accuracy of the two noninvasive techniques for the diagnosis of femoropopliteal venous thrombosis. Sensitivity, specificity, and accuracy of duplex sonography were 90%, 100%, and 97%, respectively, when compared with venography in 32 patients. Sensitivity, specificity, and accuracy of plethysmography were 100%, 63%, and 72%, respectively, when compared with venography in 25 patients. In 21 patients, plethysmography was either nondiagnostic or could not be done because of clinical difficulties. Eighteen of these patients had diagnostic duplex examinations. Duplex sonography exhibits similar sensitivity but higher specificity than plethysmography. Duplex sonography also permits diagnostic examinations in patients in whom diagnostic plethysmography cannot be performed.