Pattern and distribution of thrombi in acute venous thrombosis

The location and extent of thrombosis in the deep venous system will determine immediate and long-term outcome. During the past 3 years, we have studied by duplex scanning 833 patients with suspected deep vein thrombosis. In this group, 209 patients (25%) had a positive study. The findings relative to location and extent of involvement are as follows. (1) The right leg was involved in 35% of patients, the left leg in 48%. Bilateral involvement was noted in 17%. (2) The veins most frequently affected by deep vein thrombosis were as follows: superficial femoral in 74%, popliteal in 73%, common femoral in 58%, posterior tibial in 40%, deep femoral in 29%, greater saphenous in 19%, and the inferior vena cava in 2%; multisegment involvement was common. (3) Total occlusion was present in 82% of the patients with deep vein thrombosis, and partial occlusion in 18%. (4) Isolated occlusion of single veins was uncommon. (5) The proximal (above-knee) area was involved in 95% of the cases with deep vein thrombosis, and the calf in 40% of the cases. Isolated calf deep vein thrombosis was found in 6% of the cases with right leg involvement and in 3% for the left. (6) Total leg involvement (iliocaval, femoropopliteal, and calf) occurred in 10% of the patients. Our data confirm the fallibility of the clinical diagnosis of deep vein thrombosis. The frequent involvement of both limbs stresses the importance of not examining just the symptomatic limb. Proximal venous thrombosis (popliteal to inferior vena cava) is much more common than isolated calf vein thrombosis as a cause for symptoms and the referral for study.