Duplex scanning in the diagnosis of acute deep vein thrombosis of the lower extremity.

In a prospective study the value of duplex scanning in the diagnosis of acute femoro-popliteal thrombosis was compared to conventional contrast venography (CV) as a gold standard. A total of 126 legs in 117 patients suspected of having deep vein thrombosis (DVT) or pulmonary embolism (PE) were examined with both methods. CV and duplex scanning were diagnostic in 98.5 and 97%, respectively. Femoro-popliteal thrombosis was present in 64 legs (prevalence 54%). The sensitivity and specificity of duplex scanning were 90.6% and 94.6%, respectively. A marked improvement in sensitivity from 83.3 to 97% and overall accuracy from 88.7 to 96% was noticed between the first and second half of the study period. Of the individual duplex criteria in the diagnosis of DVT, abnormal vessel wall compressibility was the most accurate. The Doppler measurements however allow evaluation of venous areas difficult to assess with B-mode and add discrimination between partial or total vein occlusion. Duplex scanning is more accurate compared to CV in grading the anatomical extent of thrombosis. Agreement between venography and duplex scanning was found in 75% of the vein segments, in about 20% CV suggested more thrombus formation compared to duplex scanning. Thrombus in the deep femoral vein was documented by duplex scanning in 24 patients including two cases of isolated deep femoral vein thrombosis. Venography failed to visualise the deep femoral vein with sufficient diagnostic accuracy in 88% of the patients vs. 8.5% with duplex scanning. Duplex scanning is an accurate non-invasive test in the diagnosis of acute femoro-popliteal thrombosis and superior to CV in the detection of non-occlusive and deep femoral vein thrombosis.