The inferior mesenteric artery (IMA) brings oxygen-rich blood to the large intestine, specifically to the upper region of the rectum and the left colic flexure, a bend at the intestine’s left side.

The upper part of the rectum should not be confused with the anus itself. The IMA serves the part of the rectum near the descending and sigmoid colons.

As it runs its course, the IMA branches into the left colic and the superior rectal arteries, as well as the sigmoid branches.

The IMA also has a similarly named venal counterpart, the inferior mesenteric vein. This vessel drains deoxygenated blood from areas within the large intestine and it feeds into the splenic vein. From there, blood eventually moves back to the heart, pulmonary artery, and lungs for a fresh supply of oxygen and nutrients, as well as recirculation.

There is one congenital disorder that affects the inferior mesenteric artery. Some people are born with their kidneys fused. This alters the anatomy around the large intestines, and part of the resulting 'horseshoe kidney' is located below the IMA.