Congenital anomalies of the inferior vena cava.

Congenital anomalies of the inferior vena cava (IVC) and its tributaries are increasingly recognized in asymptomatic patients due to the more frequent use of cross-sectional imaging and computed tomography (CT) in particular. IVC development is a complex process involving formation of anastomoses between three pairs of embryonic veins in the 4th to 8th week of gestation. Various permutations occur in the basic venous plan of the abdomen and pelvis resulting in variants such as isolated left IVC, double IVC, and retroaortic left renal vein. The majority of these anomalies are asymptomatic but occasionally present clinically with thromboembolic complications. However, awareness of their existence is important to avoid important diagnostic pitfalls and in preoperative surgical and interventional radiological planning.