Inferior mesenteric artery

Structure

Origin

The IMA arises from the anterior aspect of the abdominal aorta.

The vertebral level of its origin is situated at L3 (subcostal plane), below the origins of the two renal arteries, 3.8 cm (1 and a half inches) above the aortic bifurcation, at the level of the umbilicus (transumbilical plane), and posterior to the inferior border of the horizontal (III) part of the duodenum.

Branches

Along its course, the IMA has the following branches:

All these arterial branches further divide into arcades which then supply the colon at regular intervals.

Relations

The IMA is accompanied along its course by a similarly named vein, the inferior mesenteric vein, which drains into the splenic vein. The IMV drains to the portal vein and does therefore not fully mirror the course of the IMA.

Distribution

Proximally, its territory of distribution overlaps (forms a watershed) with the middle colic artery, and therefore the superior mesenteric artery. The SMA and IMA anastomose via the marginal artery of the colon (artery of Drummond) and via Riolan's arcade (also called the "meandering artery", an arterial connection between the left colic artery and the middle colic artery). The territory of distribution of the IMA is more or less equivalent to the embryonic hindgut.