The anomalous left renal vein: CT appearance and clinical implications.

Persistence of portions or all of the fetal venous drainage of the left kidney may lead to a preaortic, circumaortic, or retroaortic type of left renal vein. The preaortic left renal vein, found in 85% of all cases, is almost always seen on abdominal CT scans. Its absence should alert the radiologist to look for a possible anomalous course. Awareness of associated anomalies such as duplication or transposition of the inferior vena cava makes the CT appearance of the anomalous left renal vein distinguishable from lymphadenopathy or dilated gonadal veins (14). The increased frequency of surgical procedures of the kidneys and the perirenal area has shown the need to recognize and document abnormal renal vasculature on CT scans of the abdomen.