The middle mesenteric artery.

Angiography was performed in a 70-year-old man because of a recurrence of massive hemochezia. The angiogram demonstrated a third mesenteric artery, arising from the aorta between the superior and inferior mesenteric arteries and supplying the splenic flexure. Although many variations of colonic arterial supply have been described, those involving vessels originating from the aorta separate from the celiac, superior mesenteric, or inferior mesenteric arteries are extremely rate.