Inferior pancreaticoduodenal, jejunal and ileal, ileocolic, right colic and middle colic arteries
Mnemonic
“Middle, Right, Ileocolic, Jejunal and Ileal”, working round the midgut:
- Inferior pancreaticoduodenal artery, the first branch
- Middle colic - transverse colon
- Right colic - ascending colon
- Ileocolic - terminal ileum, caecum and appendix, via the appendicular artery
- Jejunal and ileal branches, from the left side, forming the arcades
“The colics come off the right, the small bowel branches off the left.”
It arises at L1, supplies the midgut from the ampulla of Vater to two thirds along the transverse colon, and crosses the third part of the duodenum, which is why it causes superior mesenteric artery syndrome in cachectic patients who lose the retroperitoneal fat pad.
Acute occlusion causes mesenteric ischaemia, classically pain out of all proportion to the signs with a raised lactate, and it is most often embolic in atrial fibrillation.
Expansion
Arising from the aorta at L1, just below the coeliac trunk:
From the right side
- Inferior pancreaticoduodenal artery - the first branch
- Middle colic artery - to the transverse colon
- Right colic artery - to the ascending colon
- Ileocolic artery - to the terminal ileum, caecum and appendix (via the appendicular artery)
From the left side
- Jejunal and ileal branches - 15 to 18 of them, forming arcades and vasa recta
The artery passes anterior to the third part of the duodenum and the left renal vein, and posterior to the neck of the pancreas, relations that explain both superior mesenteric artery syndrome and nutcracker syndrome.
Because it arises at a shallow angle and carries high flow, it is the commonest site of embolic mesenteric ischaemia, causing pain out of proportion to the physical signs.