Restorative proctocolectomy with ileal reservoir: pathological and histochemical study of mucosal biopsy specimens.

Mucosal biopsy specimens from the ileal reservoirs of 92 patients who had undergone restorative proctocolectomy (12 with familial adenomatous polyposis, 78 with ulcerative colitis, and two with functional bowel disease) were studied. Chronic inflammation was found in almost all, as was villous atrophy of varying severity. Other changes included pyloric metaplasia and mucosal prolapse. Acute inflammatory changes and ulceration were less common but, when present, corresponded to the clinical condition of "pouchitis". A grading system was devised to score acute and chronic inflammatory changes. There was a significant increase in acute inflammatory scores in ulcerative colitis compared with those in familial adenomatous polyposis, and pouchitis was present only in patients who had had ulcerative colitis; the morphological features of pouchitis are similar to those seen in the colorectal mucosa in ulcerative colitis. Histochemical studies of mucin in the reservoirs of mucosa showed that there may have been a change from small intestinal mucin to colonic mucin.