Inferior mesenteric artery

At a glance

English

Inferior mesenteric artery

Latin (TA2)

Arteria mesenterica inferior

System

Artery

Region

Trunk

Side

Single, on the midline

About the inferior mesenteric artery

The inferior mesenteric artery is the lowest of the three unpaired gut branches of the abdominal aorta, after the coeliac trunk and the superior mesenteric artery. It leaves the front, slightly left side of the aorta at about the level of the third lumbar vertebra, behind the third part of the duodenum, a few centimetres above the point where the aorta splits into the common iliac arteries.

It runs down and to the left behind the peritoneum, on psoas major, and crosses the left common iliac artery to enter the root of the sigmoid mesocolon. Its branches are the left colic artery, which supplies the descending colon and left end of the transverse colon, two to four sigmoid arteries for the sigmoid colon, and its continuation, the superior rectal artery, which descends into the pelvis to the rectum. Each branch divides and links with its neighbours in arcades that feed the bowel wall at regular intervals.

Its field corresponds to the embryonic hindgut, from the last third of the transverse colon down to the upper anal canal. Where it meets the territory of the middle colic artery near the left colic flexure, the two systems are joined by the marginal artery running along the colon and, in some people, by a more central connecting channel (the arc of Riolan). The inferior mesenteric vein does not follow the artery all the way: it passes up to the left of the duodenojejunal flexure to join the splenic vein, so it drains into the portal system.

The artery or its branches are divided in a left hemicolectomy and in resections of the sigmoid colon and rectum. The weak point in the colic flexure supply makes this region prone to ischaemic colitis. The artery may also be covered over during repair of an abdominal aortic aneurysm. In a horseshoe kidney, the joined lower poles sit beneath the artery, which stops the kidney rising.

Course and supply

Arises from

Leaves the front of the abdominal aorta at about the third lumbar vertebra, below the renal arteries.

Ends in

Gives the left colic and sigmoid arteries and continues into the pelvis as the superior rectal artery.

Supplies

Supplies the hindgut: the left third of the transverse colon, the descending and sigmoid colon, the rectum and the upper anal canal.