The Left colic vein assists the body in the management of the blood supply of the intestines. As blood travels through the intestines it is carried away from the heart by arteries and back toward the heart by veins. The Left colic vein is a system of the inferior mesenteric vein responsible for draining the left flexure and descending colon. The left flexure is a sharp bend under the spleen where the transverse colon joins the descending colon. The descending colon is part of the large intestine. It sits on the left side that extends from the left flexure to the sigmoid colon. The inferior mesenteric vein returns blood from the rectum, sigmoid colon and descending colon, emptying the blood into the spleenic vein. The spleenic vein carries the blood away from the spleen. The valves of the Left colic vein avoid reflux by keeping the blood moving efficiently in the right direction through the bend of the left flexure and the crooked path of the sigmoid colon.