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Background & Aims: Irritable bowel syndrome (IBS) is regarded as a functional bowel disorder. Few studies have looked for histopathologic changes in the gut and only then in biopsy specimens from intestinal mucosa. Because bowel function is governed mainly by nerve plexuses in the bowel wall, we have investigated full-thickness bowel biopsy specimens in patients with severe IBS. Methods: We used a laparoscopy-assisted technique to obtain full-thickness biopsy specimens from the proximal jejunum. Tissue specimens were investigated with light microscopy using routine stainings and immunohistochemical techniques. Horizontal sectioning was done to visualize large areas of the myenteric plexus. Fifteen autopsy specimens were used as controls regarding the myenteric plexus. Colorectal adenoma controls with terminal ileum biopsy specimens and full-thickness jejunal biopsy specimens from patients with degenerative enteric neuropathy were used as control groups for intraepithelial lymphocyte counts. Results: Ten patients (2 males, 8 females) were studied. In 9 patients, we found low-grade infiltration of lymphocytes in the myenteric plexus. Lymphocytes had peri- and intraganglionic location. The mean number of lymphocytes per ganglion ranged from 1.9 to 7.1 per patient, with an overall mean of 3.4. No intraganglionic lymphocytes were found in the control group and only a few periganglionic lymphocytes (mean, 0.2). Four patients had concomitant intraepithelial lymphocytosis. Neuron degeneration was evident in 6 of 9 patients with and 1 patient without ganglionic lymphocyte infiltration. Conclusions: Our findings indicate that inflammation and neuronal degeneration in the myenteric plexus are involved in the pathogenesis of IBS. GASTROENTEROLOGY 2002;123:1972-1979

BACKGROUND & AIMS: Some patients with ulcerative colitis (UC) receiving an ileal pelvic pouch with ileoanal anastomosis (IPAA) develop persistent severe villous atrophy in the pouch mucosa. To investigate if mucosal atrophy indicates a risk for subsequent neoplastic transformation of the ileal pouch mucosa, a follow-up study was undertaken. METHODS: Seven patients with UC and an IPAA in whom persistent severe atrophy (type C) developed and 14 control patients with no or only slight atrophy (type A) were prospectively surveyed by flexible videoendoscopy with multiple biopsies for assessment of possible neoplastic changes. RESULTS: The median time of the pouch in function was 9 years for both groups. Dysplasia was found in 5 of 7 patients in the type C group (71%) compared with none in the type A group (P < 0.001). Four patients had low-grade dysplasia, and 1 patient had sequential multifocal development into high-grade dysplasia. Multifocal DNA aneuploidy was found in 2 patients, 1 with low-grade and 1 with high-grade dysplasia. CONCLUSIONS: Patients with UC and a long- standing IPAA who develop persistent severe mucosal atrophy are at risk also of neoplastic transformation of the pouch mucosa. (Gastroenterology 1997 May;112(5):1487-92)