Diagnosing deep vein thrombosis by Doppler ultrasound and impedance plethysmography

To evaluate the diagnostic accuracy of Doppler ultrasound (DU) and impedance plethysmography (IPG) in deep vein thrombosis (DVT), hospital records of 904 patients having 1,084 studies of blood flow in the lower extremities were retrospectively reviewed, and 544 were found abnormal. In 128, both DU and IPG showed abnormalities, 86 had only DU evidence of abnormalities, and 330 had only IPG abnormalities. Fifty-one patients with abnormal results of both DU and IPG studies had ascending phlebography, which in 47 documented the presence of DVT, for a diagnostic accuracy of 92%. On the basis of DU/IPG testing, or extenuating clinical circumstances, 135 patients considered at high risk for pulmonary emboli had ventilation-perfusion lung scans. Of these, 44 had roentgenographic evidence of pulmonary emboli. While ascending phlebography remains the definitive study for documenting the presence of DVT, DU/IPG testing has a high accuracy rate, is noninvasive, readily reproducible, inexpensive, and simple to perform. When results of DU/IPG studies are abnormal a baseline ventilation lung scan should be done which, if questionable, should be followed by pulmonary arteriography.