Histological Features of Ileitis Differentiating Pediatric Crohn Disease From Ulcerative Colitis with Backwash Ileitis

Abstract Background/aim Pediatric ileocolonic Crohn disease (CD) may be difficult to distinguish from ulcerative colitis (UC) with backwash ileitis (BWI). The primary aim of the study was to determine the probability of CD in children with a confluent colitis and ileitis when newly diagnosed with inflammatory bowel disease (IBD). Methods A retrospective observational study of 100 newly diagnosed patients with IBD was performed. Two pathologists reviewed ileal biopsy specimens for 8 histological features. Biopsy and clinical features were evaluated for predictive ability of a final diagnosis of CD. Results The presence of crypt distortion, lamina propria (LP) expansion, and acute LP inflammation combined with 4 clinical variables in multivariate regression analysis had adequate discriminative validity when comparing the mean probability of a final CD diagnosis between CD and not-CD groups (0.90 vs. 0.59, p value 0.001). When crypt distortion, LP expansion, and acute LP inflammation are present in any combination, the sensitivity and specificity for presence of CD ranges 38.4–57% and 92.9–100%, respectively. Conclusions Combining histological features of ileitis and clinical variables can adequately discriminate between the presence and absence of Crohn disease in children who present with confluent colitis and ileitis. Combined presence of certain histological features has high specificity for CD.