Impedance plethysmography: correlation with contrast venography

Impedance plethysmography is a noninvasive, indirect test for deep venous occlusion in the lower limbs. The results of ascending contrast venography impedance plethysmography have been compared in 315 limbs. Impedance plethysmography was positive in 77 of 79 limbs with acute deep vein thrombosis proximal to the calf. It was positive in 6 of 27 limbs with clot isolated in the calf. Only 7 false-positive plethysmograms were found in 161 normal contrast venograms. The clinical implications of these data are discussed.