['Commonly accepted risk factors for colorectal carcinoma (CRC) in ulcerative colitis are duration and extent of disease. By identifying still unknown risk factors, surveillance strategies may be improved further. We investigated whether backwash ileitis is also a factor associated with CRC in ulcerative colitis.', 'Five hundred ninety consecutive patients with ulcerative colitis who received restorative proctocolectomy were classified into 3 groups: (1) pancolitis with backwash ileitis, (2) pancolitis without backwash ileitis, and (3) left-sided colitis. The association with CRC was analyzed in these 3 groups of patients. As further risk factors, we investigated disease duration, dysplasia, primary sclerosing cholangitis, age at diagnosis of disease, disease activity, and gender. Univariate and multivariate logistic regression were used for analysis.', 'CRC was diagnosed in 11.2% of all patients. CRC was found in 29.0% of 107 patients in group 1, compared with 9.0% of 369 patients in group 2, and in 1.8% of 114 patients in group 3 (P < 0.001). Cancer patients in group 1 showed significantly more multiple tumor growth (45.2%) than patients in group 2 (24.2%) and group 3 (0%) (P = 0.041). Estimating the relative risk for CRC in the multivariate analysis, patients in group 1 showed a significantly higher odds ratio than patients in groups 2 and 3 (odds ratio: 19.36 vs. 9.58 vs. 1; P < 0.001). High-grade dysplasia, low-grade dysplasia, disease duration of more than 10 years, and disease duration of less than 10 years in patients older than 45 years were further factors with significantly increased risk (odds ratios: 21.69, 6.36, 3.63, 4.37), but primary sclerosing cholangitis was not (P = 0.080). However, primary sclerosing cholangitis was strongly associated with backwash ileitis.'] Is backwash ileitis strongly associated with colorectal carcinoma in ulcerative colitis?