Colonic Metaplasia in the Ileal Pouch is Associated with Inflammation and is Not the Result of Long-Term Adaptation
Abstracts
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Background: Ileal pouch-anal anastomosis (IPAA) is the preferred surgical therapy for chronic ulcerative colitis (CUC.) Previous studies have demonstrated morphologic changes in pouch mucosa such as villous atrophy and crypt hyperplasia. These changes have been labeled colonic metaplasia. The aims of this study were to determine whether these changes represent normal long-term adaptation of the non-diseased pouch or rather are present only in the setting of inflammation. Methods: 55 patients status post IPAA for CUC underwent pouchoscopy five years after IPAA. 24 patients underwent pouchoscopy for surveillance, had no history of pouchitis and no clinical symptoms of pouchitis at the time of evaluation. Thirty-one patients had a history of pouchitis, and clinical symptoms at the time of evaluation. Biopsies were evaluated by a single, blinded pathologist. Degree of epithelitis, cryptitis, stromal inflammation, vascularity, and ulceration were determined, and a summated Inflammation Score was calculated based on these variables (maximum score 28.) Degree of villous atrophy (0-3) and crypt hyperplasia (0-3) were determined and a summated Colonic Metaplasia Score was calculated (maximum score 6.) Maximal colonic metaplasia was represented by a score of 3 for villous atrophy (complete villous atrophy) and a score of least 2 for crypt hyperplasia. Results: The Inflammation Score was greater in the pouchitis group, 12.6?1.2, vs. the non-pouchitis group, 4.04?0.6 (P<0.0001). The Colonic Metaplasia Score was greater in the pouchitis group 4.32?0.26 vs. 1.67?0.34 (P<0.0001). In both groups, the Colonic Metaplasia score strongly correlated with the Inflammation Score, Spearman coefficient r=0.84, p<0.0001. The percentage of biopsies showing maximal colonic metaplasia was 14/31 (45%.) in the pouchitis group vs. 1/25(4%) in the non-pouchitis group (p=0.0007.) The one patient with maximal colonic metaplasia in the non-pouchitis group also had the highest Inflammation Score in this group. There was no evidence of dysplasia in any of the biopsies. Conclusion: Patients without a history of pouchitis or symptoms of pouchitis have only a minimal degree of villous atrophy and crypt hyperplasia. These long-term morphologic changes in the ileal pouch, which have been termed colonic metaplasia, are much more pronounced in the setting of inflammation, and correlate strongly with the degree of inflammation present. Colonic metaplasia does not represent normal adaptation of ileal pouch mucosa. |
