Injury to the superior mesenteric artery (SMA) during nephrectomy is a rare but potentially catastrophic complication. SMA injury during nephrectomy most commonly occurs with large tumors or bulky lymphadenopathy, with inadvertent injury or mistaken ligation of the SMA instead of the renal artery. Failure to recognize and repair an SMA injury results in ischemic bowel and death for most patients. We report a case of SMA ligation during left nephrectomy for xanthogranulomatous pyelonephritis, review the intraoperative evaluation of suspected SMA injury, and describe our vascular repair using a vein patch from the native left renal vein.