The origin of lower extremity deep vein thrombi in acute venous thrombosis

Background It has been taught that most deep venous thromboses (DVT) begin in the deep veins of the calf and propagate proximally. The duplex ultrasound scan, with its noninvasive characteristics and accuracy, has brought this premise into question. The purpose of this study was to determine the pattern and distribution of acute DVT as well as the different types of thrombi. Methods We performed a retrospective review of all duplex scans ordered for a diagnosis of acute lower extremite DVT at a 200-bed hospital over a 5-year period. Results There were 3,585 examinations performed on 2,654 patients. There were 461 patients (17.4%) with a venous thrombosis. Four types of venous thrombosis were identified: an isolated thrombosis in one venous segment (34%), a thrombosis extending over two or more contiguous segments (52%), multiple thromboses in noncontiguous segments (8%), and bilateral thrombi in different locations (6%). Conclusion Calf vein thrombi represented 24% of all DVT. Thrombi in the major veins of the thigh and popliteal space without calf involvement were present in 49% of all DVT. The data in this paper indicate that most significant deep venous thromboses do not begin in the calf but instead arise in the proximal thigh or groin.