Morphology, mucin histochemistry and crypt cell kinetics of ileal mucosa in an experimental model.

An animal model was used to investigate the morphology, mucin hisotchemistry and crypt cell kinetics of ileal pouch mucosa. Forty-eight Sprague Dawley rats underwent control laparotomy with ileal transection and reanastomosis, leocolic transposition of a 3 cm segment of ileum or colectomy and ileal pouch rectal anastomosis. Animals were sacrificed 20 weeks later. Partial villous atrophy and chronic inflammation were found in both transposed and pouch ileum. Although mucin histochemistry showed patchy colonic type changes, overall there was preservation of a small bowel pattern in both transposed and pouch ileum. Crypt cell mitosis, measured by bromodeoxyuridine labelling index, was reduced in ileal pouch mucosa. These data indicate that predominantly villous atrophy, rather than colonic metaplasia occurs in ileal pouch mucosa and suggest that there is a low propensity for dysplastic change in such mucosa.