BACKGROUND: Previous studies of short-term surgical outcomes after preoperative exposure to anti-TNF therapy in ulcerative colitis (UC) patients who have undergone IPAA have been conflicting. We sought to determine whether preoperative exposure to anti-TNF therapy affects histological measures of fibrosis in the colorectum, which may be a potential factor in adverse anastomosis complications following IPAA surgery.||METHODS: Individuals who received infliximab as maintenance therapy and who received their last dose within 180 days of the first stage of IPAA were selected. The control group comprised UC patients who were not exposed to anti-TNF therapy, matched by age, sex, BMI, disease duration, albumin levels, and post-operative leak outcome. Hematoxylin and eosin- (H&E) and trichrome-stained slides from the most distal, well-oriented, full-thickness section of colorectum from each patient's total colectomy specimen were evaluated. Blinded assessment of the degree of fibrosis in the lamina propria, the submucosa, the submucosa immediately adjacent to the muscularis propria, and the subserosa was performed by a single observer using a semi-quantitative pictorial scale.