Distribution of acute lower extremity deep venous thrombosis in symptomatic and asymptomatic patients: imaging implications.

The ability of noninvasive imaging modalities to diagnose lower extremity DVT depends, in part, on the anatomic location of the thrombus. To define the pattern of thrombus formation in symptomatic and asymptomatic high-risk patient populations, 172 consecutive lower extremity venograms were submitted to blinded, retrospective interpretation. Acute DVT was present in 59 venograms (34 symptomatic and 25 asymptomatic patients). Among symptomatic patients with acute DVT, 26 of 34 (76%) patients had an above-knee thrombus and only eight of 34 (24%) patients had a thrombus isolated to the calf. In comparison, only three of 25 (12%) asymptomatic patients with DVT had an above-knee thrombus and 22 of 25 (88%) patients had a thrombus isolated to the calf veins (most involving only one venous segment). Failure to examine the calf veins, particularly in asymptomatic patients, would result in missing at least half of patients with DVT. Alternatively, since all cases of iliac vein DVT extended into the femoropopliteal segment, failure to visualize the iliac veins is unlikely to miss patients with DVT. Our results suggest merit to routine examination of the deep femoral, anterior tibial, and particularly the soleal (but not the gastrocnemius) veins and also to use of an imaging technique to detect congenital duplications of the superficial femoral and popliteal veins.