Left colic, sigmoid and superior rectal arteries
Mnemonic
“Left colic, Sigmoid, Superior rectal”, three branches for the hindgut:
- Left colic - descending colon
- Sigmoid branches
- Superior rectal - the terminal branch, to the upper rectum
It arises at L3, and supplies from two thirds along the transverse colon to the upper anal canal.
The marginal artery of Drummond runs along the mesenteric border of the whole colon, linking superior and inferior mesenteric territories, with the arc of Riolan as a more central connection.
The splenic flexure is the watershed between the two territories and the commonest site of ischaemic colitis, presenting with left sided pain and bloody diarrhoea, with thumbprinting on abdominal radiograph.
The rectosigmoid junction (Sudeck’s point) is the second watershed, between the last sigmoid branch and the superior rectal artery.
Expansion
Arising from the aorta at L3:
- Left colic artery - to the descending colon and splenic flexure
- Sigmoid arteries - two to four, to the sigmoid colon
- Superior rectal artery - the terminal continuation, to the upper rectum
Its territory is the hindgut: the distal third of the transverse colon, the descending and sigmoid colon, and the upper rectum.
Two boundaries coincide here. The arterial watershed with the superior mesenteric artery lies at the splenic flexure, and the venous watershed between portal and systemic drainage lies in the rectum, where the superior rectal vein (portal) meets the middle and inferior rectal veins (systemic).
The inferior mesenteric artery can be ligated at its origin in colorectal cancer surgery because the marginal artery maintains collateral flow.