In human anatomy, the inferior mesenteric artery (IMA) is the third main branch of the abdominal aorta and arises at the level of L3, supplying the large intestine from the distal transverse colon to the upper part of the anal canal. The regions supplied by the IMA are the descending colon, the sigmoid colon, and part of the rectum.

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:

Branch notes left colic artery supplies descending colon sigmoid branches the most superior being described as 'the superior sigmoid artery' superior rectal artery effectively the terminal branch of the IMA (the continuation of the IMA after all other 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.

Clinical significance The IMA and/or its branches must be resected for a left hemicolectomy.

A horseshoe kidney, a common (1 in 500) anomaly of the kidneys, will be positioned below the IMA.

Additional images

See also Superior mesenteric artery

References

External links Lotti M. Anatomy in relation to left colectomy - "Branches of the inferior mesenteric artery." - "Posterior Abdominal Wall: Branches of the Abdominal Aorta"

- "Posterior Abdominal Wall, Dissection, Anterior View"