Left Iliac Vein Compressions and Venous Hemodynamic Changes

Purpose: Left iliac vein compression is a risk factor for deep vein thrombosis (DVT) and often can be symptomatic. We wanted to know the incidence of left iliac vein compressions in the general population and the relationship between iliac vein compression and outflow fraction of the lower extremities. Methods: 1,523 cases examined with abdomen pelvis CT were included in this study. Left iliac vein compression was calculated as the diameter of left common iliac vein at the site of maximal compression divided by the diameter of the uncompressed caudal common iliac vein. These cases were divided into 4 groups by the degree of iliac vein compression. In addition, left lower extremity venous outflow fractions in 106 patients with abdomen pelvis CT images were recorded and analyzed. Results: The number and mean age of each group (group 1, 2, 3 and 4) were 351 (23%) & 62.3±13.4, 426 (28%) & 57.7±16.1, 529 (35%) & 50.1±20.4 and 217 (14%) & 40.7±22.9, respectively. While the age of patients was decreasing, the occurrence of left iliac vein compression increased (P<0.01). The mean left low extremity venous outflow fractions of each group (group 1, 2, 3 and 4) was 27.9±6.9%, 26.9±6.4%, 25.9±6.7% and 19.1±6.6%, respectively. The mean outflow fraction of group 4 was significantly lower than that of other groups (P<0.01). There was a tendency that the more left iliac vein compression increased, the more outflow fraction decreased (P=0.011). Conclusion: In 14% of 1,523 cases, there were severe left iliac vein compressions, more than 75% diameter, and the mean outflow fraction of that was lower than in others. Further study is needed to realize the relationship between left iliac vein compression and DVT. (J Korean Surg Soc 2009;77:404-409)