The anatomy of deep venous thrombosis of the lower extremity

Background: The diagnosis, treatment, and long-term sequelae of lower extre mity deep venous thrombosis (DVT) depend on the anatomic location and exten t of the process, yet a lack of such fundamental knowledge has limited the development of effective protocols for managing patients with DVT. Methods: Venograms with evidence of acute DVT were evaluated, and the exten t of the thrombotic process was recorded and correlated with the clinical p resentation. Thrombi were classified according to the venous segments invol ved and to the thrombus' isolation to one segment or multiple segments. The left-to-right ratio of the DVT was assessed for various etiologic subgroup s. Results: Among 2762 venograms performed in 2541 patients over a 10-year per iod, there were 885 cases (34.8%) of DVT documented. Of these cases, 344 ca ses (39%) were idiopathic, 307 cases (35%) were postoperative, 84 cases (10 %) occurred in the setting of malignancy, and 70 cases (8%) occurred as the result of trauma. Distal thrombi were more common than proximal thrombi, w ith calf involvement in 734 patients (83%), femoropopliteal involvement in 470 patients (53%), and iliac involvement in 75 patients (9%). The most com mon site of thrombus was the peroneal vein, which was involved in 595 patie nts (67%). The ratio of left-to-right-sided DVT was 1.32:1 overall but was greater for proximal thrombi, with a ratio of 2.4:1 for iliac DVT versus 1. 3:1 for infrainguinal DVT. The preponderance of left-sided DVT appeared to be related to the high-frequency, left common iliac vein involvement; the l eft-to-right ratio was much closer to equality (1.09:1) for isolated infrai nguinal DVT. The anatomic configuration of the DVT mas correlated with the etiologic subgroup; postoperative DVTs were more often distal, whereas DVT developing in the setting of malignancy was more frequently proximal and of ten right sided. Proximal, left-sided DVTs were common in the idiopathic su bgroup, presumably as a result of undiagnosed left iliac vein webs. Conclusions: The frequency of distal vein involvement greatly exceeds that of proximal involvement in patients with DVTs. Proximal DVTs are more frequ ently left sided, whereas distal DVTs occur with a more equal left-to-right distribution. The anatomic extent of DVTs appears to depend on the etiolog y of the process. These observations may shed Light on the pathophysiology of venous thrombosis. The findings are of value in planning therapeutic int erventions directed at venous recanalization.