Multidetector computed tomography of iliac vein variation: prevalence and classification

To determine the prevalence of iliac venous variations and to classify the variations using multidetector computed tomography (MDCT). MDCT images of 2,488 patients were retrospectively reviewed. Iliac venous variations were documented and classified with regard to internal iliac vein (IIV) drainage patterns, the presence of interiliac communicating veins and inferior vena cava (IVC) anomalies associated with iliac venous variations. The variation prevalence rates were analyzed and calculated. The incidence of iliac venous variations was 20.9 %, and these were classified into eight types: normal, 79.1 % (type 1); high joining of the IIV to the ipsilateral external iliac vein, 8.7 % (type 2); the IIV joining to the contralateral common iliac vein (CIV), 2.3 % (type 3); IIVs forming a common trunk, 0.9 % (type 4); communicating vein from the IIV to the contralateral CIV or IIV, 7.8 % (type 5); double IVC with or without a connecting vein, 0.9 % (type 6); left IVC, 0.1 % (type 7); and fenestration of the CIV, 0.4 % (type 8). There were subtypes which varied according to right- or left-side variation and the status of smaller connecting veins. No statistical difference in the prevalence rate was found between men and women (p = 0.365). Iliac venous variations are frequently seen on MDCT and can be classified into 8 types.