Background: Both Crohn's disease ileal ulcers and indomethacin-induced jejunal ulcers in the rat have a predilection for the mesenteric margin of the bowel wall. Unlike the anti-mesenteric margin, the mesenteric margin is supplied by small end-arteries that might render it more sensitive to ischaemic injury.
Aim: To examine, in both situations, the histological relationship between the precise localization of small bowel ulcers and the mesenteric margin.
Methods: Ileal Crohn's disease ulcers identified in surgical resection specimens (n=5) and indomethacin-induced lesions in the rat jejunum (n=6) were examined macroscopically and histologically.
Results: In both the human ileum and the rat jejunum, ulcers occurred consistently along the mesenteric margin, with the most extensive mucosal injury occurring at two adjacent sites on either side of the midline of this margin. At these two sites, feeding arteries entered the muscularis propria.
Conclusions: For anatomical reasons apparently related to the vasculature of the human and rodent small bowel, specific sites along the mesenteric margin are susceptible to Crohn's disease ulceration and NSAID damage, respectively.