Pattern of mucosal adaptation in acute and chronic pouchitis

PURPOSE: Variant pathological changes have been observed in ileoanal, pouch es, including inflammation, villous atrophy, and crypt hyperplasia. Therefo re, we investigated the type and degree of mucosal adaptation in patients w ith ulcerative colitis and familial adenomatous polyposis. METHODS: Forty-t wo patients With ulcerative colitis and 14 patients with familial adenomato us polyposis with ileoanal pouches were assessed. Samples were taken from t hree months to eight years after creation of an ileoanal pouch. Mucosal arc hitecture was examined by morphometry after microdissection. RESULTS: Struc tural changes of the mucosa can be categorized into three groups. Compared with preoperative values, patients without pouchitis (73 percent) has only minor decrease of villous length (402 mu m vs. 540 mu m) and increase in cr ypt depth (274.5 mu m vs. 177 mu m). In patients with acute pouchitis (20 p ercent), a slight increase in villous length (477 mu m vs. 402 mu m) and pr onounced crypt hyperplasia (376 mu m vs. 274.5 mu m) was observed compared with noninflamed ileoanal pouches. In contrast, in patients with chronic po uchitis (7 percent), severe villous atrophy(62.5 mu m) and crypt hyperplasi a (543 mu m) was found. CONCLUSIONS: Minor structural changes of ileoanal p ouch mucosa develop early as an adaptive response to a new environment. Onl y in a small group of patients with chronic pouchitis does severe villous a trophy and crypt hyperplasia of the ileoanal pouch mucosa develop, most lik ely as a consequence of mucosal inflammation.