We report the case of a patient who was transferred to our facility after a CT scan obtained at a local hospital revealed a leaking abdominal aortic aneurysm. Review of the scan showed an aorto-left renal vein fistula. Knowing this fistula was present made the operative repair of the aneurysm and control of the fistula much more straightforward than might otherwise have been the case. Although relatively rare, major anomalies of the renal veins and perirenal vena cava should be borne in mind when operating on the abdominal aorta. This case illustrates the merit of contrast-enhanced CT scanning prior to aortic surgery.