Early changes of ileoanal pouch mucosa in patients with ulcerative colitis

Background/aims Following closure of the protective ileostomy the mucosa of ileoanal pouches undergoes characteristic changes, which are thought to be caused by the new luminal environment. Conventional histopathology and imm unohistochemical markers were compared in serial pouch biopsies from patien ts with ulcerative colitis (UC) in the early period of function. Methods Biopsy specimens were obtained from nine patients during ileostomy closure, 24 h after the first bowel action, then 6 days, 6 weeks and 3 mont hs postoperatively, Cryostat sections were stained with haematoxylin and eo sin (H&E) for assessment of mucosal inflammation and morphometry, and for l ymphocyte subtypes (CD3, CD4, CD8), macrophages (CD68), common leucocyte an tigen (CD45), and HLA-DR, using a three-stage immunoperoxidase reaction. Results Within 5 days of pouch function the index for mucosal atrophy (vill ous height/total mucosal thickness ratio) decreased significantly from a me dian (range) of 0.66 (0.39 - 0.69) to 0.52 (0.37 - 0.61)(P = 0.02), Intraep ithelial lymphocyte counts diminished from 10.1 (5.6 - 21.1) to 7.0 (2.2 - 8.2)(P = 0.007) per 100 epithelial cells and remained so. In the lamina pro pria, apart from a transient increase in CD3 positive cells at 5 days (from 92.7 (58 - 165) to 100.5 (57 - 234) per unit area; P = 0.038), no signifia nt changes were observed. H&E grading and HLA-DR expression remained unchan ged. Conclusions While there was no significant change in mucosal morphology and mucosal leucocyte subpopulations after 24 h of pouch function, the ileal p ouch mucosa in UC patients had responded significantly within 5 days. Furth er studies into cell function and signalling are required. (C) 2000 Lippinc ott Williams & Wilkins.