Thrombosis in unusual sites of the lower extremity veins.

BACKGROUND: Thrombosis in unusual locations in the lower extremity veins has not been assessed. These veins are not imaged routinely and therefore information about them is lacking.
METHODS: This study was designed to evaluate the natural history of deep vein thrombosis (DVT) in unusual sites. Patients with DVT in all thigh veins but the femoral vein were included. Patients with thrombi in any other vein in the first examination and those with history of DVT were excluded. Duplex ultrasound (DU) examination was performed to exclude thrombosis in the lower extremity in patients with signs and symptoms of venous thromboembolism and also in high-risk, asymptomatic patients. All veins from the distal external iliac vein to the lower calf were imaged. The deep femoral, femoropopliteal, lateral thigh, sciatic, and muscular thigh veins were examined. These patients were followed at 1 week, 1 month, 6 months, 1 year, and yearly thereafter, for thrombus propagation, resolution, and reflux.
RESULTS: Among the 15,850 DU performed in the vascular laboratory at Loyola University Medical Center, in a 10-year period to rule out DVT, 2568 (16.2%) were positive and 14 cases (7 males, 0.54% among the patients with DVT and 0.088% among the entire population) involved thromboses in unusual locations. Ten cases involved the left lower extremity and four the right. The unusual DVT cases were associated with medical and surgical conditions or were idiopathic in 11 patients, whereas three had Klippel-Trenaunay syndrome (KTS). The veins involved in the first group of patients were the deep femoral (8), the femoropopliteal (2), and the deep external pudendal (1). The patients with KTS had involvement of muscular thigh veins (1), and the lateral thigh vein and the sciatic vein (2). Thrombi propagation with extension to the common femoral vein was seen in four of the 14 patients: two from the deep femoral vein, one from the femoropopliteal vein, and one from the deep external pudendal vein. There were two incidences of pulmonary embolism (PE) one of which was fatal. At final follow-up, two patients developed recurrent DVT and nine had signs and symptoms of chronic venous disease.
CONCLUSIONS: The involvement of the studied veins in DVT is extremely rare. Thrombosis in these veins can follow the natural course of thrombosis in the more usual locations and is associated with lethal incidences of PE. Therefore, the association of these veins with all the grave sequelae of thromboembolic disease suggests that inclusion of these veins in routine lower extremity duplex scans would be beneficial.