Evaluation of internal iliac vein branching variations in the pelvis using MDCT with precisely defined scanning parameters

Background: A precise understanding of pelvic anatomy is indispensable for performing pelvic surgery with both safety and oncologic adequacy. Several studies have reported that the internal iliac vein (IIV) exhibits numerous anatomical variations. However, no studies have investigated its venous anatomy using a contrast-enhanced computed tomography (CT) protocol with stricter contrast timing and thinner slice settings. Methods: This retrospective study included 106 consecutive patients with rectal cancer who underwent surgery at our institution from 2021 to 2022. All patients underwent contrast-enhanced computed tomography using a protocol optimized for contrast timing and thin-slice reconstruction. The branching patterns of the IIV were evaluated. Results: Anomalous branching patterns of the IIV were observed in 44.3% of cases. Multiple IIVs were found in one or both halves of the pelvis. In some cases, the IIV formed communicating channels with the median sacral vein, and in others, a single vein connecting the duplicated inferior vena cava was identified. Conclusion: This study demonstrated various anatomical variations of the IIV by using a high-resolution contrast-enhanced CT protocol. These findings improve the understanding of pelvic venous anatomy and provide valuable information that may assist surgeons in preoperative planning and safer performance of pelvic surgery.