An image analysis of the major angles along the pathway of iliac veins involved in endovenous interventions

Abstract

Objective: The specific anatomic characteristics of the iliac veins are often important reasons for stent failure. However, to the best of our knowledge, the inherent angles and configurations of the iliac veins have not been thoroughly studied.

Methods: Fifty patients without venous diseases who had undergone computed tomography urography for diagnosis of urolithiasis were included in this study. The pathways of the iliac veins were mapped out, and the major angles were measured. The factors associated with steep angles were also evaluated.

Results: There were two relatively constant angles on the right side and three on the left side along the common femoral vein, external iliac vein, and common iliac vein. All these were measured with the patients in the supine position. The angles at the inguinal region (γ) and internal-external iliac vein confluence (β) were at similar sites for both sides. There was a third angle in front of the fifth vertebra for the left side (α). The γ angle was 125.03 ± 11.68 degrees for the right side and 122.26 ± 9.64 degrees for the left side. The β angle was 136.91 ± 14.24 degrees for the right side and 125.61 ± 20.76 degrees for the left side. According to the β angle of the left side, the iliac veins could be categorized into three types. For type I, the angle was >150 degrees (14% [7/50]). For type II, it was 120 to 150 degrees (50% [25/50]). For type III, it was ≤120 degrees (36% [18/50]). The angles between the anterior border of the fifth vertebra and pelvic inlet plane (0.866; 95% confidence interval, 0.777-0.966) and age (1.087; 95% confidence interval, 1.004-1.177) were related to type III configurations on multilogistic regression analysis.

Conclusions: There were several relatively constant angles along the pathway of the iliac veins. The pathway of the left side was more complex than that of the right side. This difference in the angles might be related to the patients' age and bone structures. These angles should be considered in planning iliac vein stenting as well as in designing stents specifically for the iliac veins.

Keywords: Anatomy; Angle; Iliac vein; Pelvis; Stent; Vertebra.