The jejunal arteries (4-6 branches) and ileal arteries (6-12 branches) arise from the left side of the superior mesenteric artery and run in the mesentery in fan-shaped arcades. The jejunal arcades are typically simple, with long vasa recta, producing a rich mucosal fold pattern. The ileal arcades are more complex, with multiple tiers and shorter vasa recta, reflecting the ileum's greater length. The vasa recta terminate as the terminal arterioles supplying the bowel wall.
The jejunal and ileal vascular arcades determine the safe length of bowel that can be resected while maintaining adequate perfusion to the anastomotic ends. The mesenteric vascular check during bowel resection involves transillumination of the mesentery to identify the arcades and assess viability. Short bowel syndrome results from extensive small bowel resection compromising the remaining absorptive length. In acute mesenteric ischaemia from SMA occlusion, the jejunal and ileal arteries are all affected, causing pan-small-bowel infarction unless rapidly treated.
Embolism or thrombosis of the SMA trunk cuts off flow to the jejunal and ileal arteries simultaneously, producing catastrophic pan-small-bowel infarction with severe abdominal pain out of proportion to signs, requiring emergency SMA embolectomy or thrombectomy and resection of necrotic bowel within hours of onset.
Adequate small bowel resection requires transection of the mesentery at the appropriate arcade tier to ensure the anastomotic ends have viable straight vasa recta; insufficient arcade preservation produces ischaemic ends leading to anastomotic breakdown, while excessive resection risks short bowel syndrome.
