The anatomy of deep venous thrombosis of the lower extremity

The diagnosis, treatment, and long-term sequelae of lower extremity deep venous thrombosis (DVT) depend on the anatomic location and extent of the process, yet a lack of such fundamental knowledge has limited the development of effective protocols for managing patients with DVT.

Venograms with evidence of acute DVT were evaluated, and the extent of the thrombotic process was recorded and correlated with the clinical presentation. Thrombi were classified according to the venous segments involved and to the thrombus' isolation to one segment or multiple segments. The left-to-right ratio of the DVT was assessed for various etiologic subgroups.

Among 2762 venograms performed in 2541 patients over a 10-year period, there were 885 cases (34.8%) of DVT documented. Of these cases, 344 cases (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, with calf involvement in 734 patients (83%), femoropopliteal involvement in 470 patients (53%), and iliac involvement in 75 patients (9%). The most common site of thrombus was the peroneal vein, which was involved in 595 patients (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 left-to-right ratio was much closer to equality (1.09:1) for isolated infrainguinal DVT. The anatomic configuration of the DVT was correlated with the etiologic subgroup; postoperative DVTs were more often distal, whereas DVT developing in the setting of malignancy was more frequently proximal and often right sided. Proximal, left-sided DVTs were common in the idiopathic subgroup, presumably as a result of undiagnosed left iliac vein webs.

The frequency of distal vein involvement greatly exceeds that of proximal involvement in patients with DVTs. Proximal DVTs are more frequently left sided, whereas distal DVTs occur with a more equal left-to-right distribution. The anatomic extent of DVTs appears to depend on the etiology of the process. These observations may shed light on the pathophysiology of venous thrombosis. The findings are of value in planning therapeutic interventions directed at venous recanalization.