Inferior mesenteric vein

At a glance

English

Inferior mesenteric vein

Latin (TA2)

Vena mesenterica inferior

System

Vein

Region

Trunk

Side

Single, on the midline

About the inferior mesenteric vein

The inferior mesenteric vein is part of the portal system. It collects blood from the distal third of the transverse colon, the descending and sigmoid colon, the rectum and the upper anal canal, and returns it to the liver by way of the splenic and portal veins. It is the venous partner of the inferior mesenteric artery, although the two separate as they climb.

It starts in the pelvis as the superior rectal vein, which leaves the rectum and crosses the left common iliac vessels. The vein then ascends behind the peritoneum on psoas major, lying to the left of its artery and further from the midline. Higher up it passes lateral to the duodenojejunal flexure, under the peritoneal fold there, and slips behind the body of the pancreas. Its usual ending is in the splenic vein, behind the middle of the pancreatic body. The splenic vein in turn meets the superior mesenteric vein, and the portal vein begins there.

Its tributaries match the branches of the inferior mesenteric artery: the left colic vein from the descending colon, several sigmoid veins, rectosigmoid veins and the superior rectal vein. In some people the vein drains instead into the angle where the superior mesenteric and splenic veins meet, or directly into the superior mesenteric vein.

The superior rectal vein connects within the wall of the rectum and anal canal with the middle and inferior rectal veins, which drain to the systemic circulation. This makes the anorectal region one of the sites where portal and systemic veins meet and where varices may form in portal hypertension. The vein runs close to the pancreas, so it can be injured when surgeons operate on the pancreatic body or tail; if it is badly torn it can be tied off safely, because the large bowel has other drainage routes. Surgeons also use it as a landmark when mobilising the left colon, and it is often divided near the duodenojejunal flexure during colectomy.

Course and drainage

Begins at

Begins in the pelvis as the continuation of the superior rectal vein.

Drains into

Ascends on the left side behind the peritoneum and usually opens into the splenic vein behind the body of the pancreas; sometimes it joins the splenomesenteric confluence or the superior mesenteric vein.

Drains

Drains the left third of the transverse colon, the descending and sigmoid colon, the rectum and the upper anal canal into the portal system.