Laparoscopic surgery for rectal cancer with a coexisting Retzius shunt and inferior mesenteric arteriovenous malformation: A case report.

A coexisting short-circuit from the inferior mesenteric vein (IMV) to the inferior vena cava, known as a Retzius shunt, and arteriovenous malformation (AVM) of the inferior mesentery are extremely rare conditions. We encountered a case of rectal cancer with coexisting Retzius shunt and inferior mesenteric AVM successfully treated with laparoscopic surgery. Contrast computed tomography (CT) in a 62-year-old man with rectal cancer showed multiple dilated veins at the mesenterium of the descending sigmoid colon. These dilated veins were connected between the IMV and the left renal vein. A diagnosis of Retzius shunt was made, and laparoscopic low anterior resection with lymph node dissection was performed. A pathological examination of the colonic mesenterium revealed AVM communicating with the dilated IMV and Retzius shunt. The preoperative evaluation of aberrant vessels by three-dimensional CT is particularly useful for patients with vascular malformations to ensure safe laparoscopic surgery.