Retroaortic left renal vein and its implications in abdominal aortic surgery.

The embryological development of the retroperitoneal venous system is a complex process. As a result, the anatomy of the inferior vena cava (IVC) and renal veins shows extensive variability. Improper completion of this process may lead to six anatomical variants: retroaortic left renal vein (LRV) types I and II, circumaortic venous collar, duplication of the IVC, transposition or left-sided IVC, and preaortic iliac confluence. All six are infrequent, but may be encountered during abdominal aortic reconstruction and pose challenging problems to the operating surgeon. Failure to appreciate these anomalies can lead to inadvertent injury and major venous bleeding. Preoperative diagnosis can be made on a CT scan, but this is not always performed prior to aortic surgery. In this report, we analyze two cases of retroaortic LRV complicating abdominal aortic aneurysmectomy, describe the most common infrarenal venous anomalies encountered during aortic surgery, and briefly review the literature.