Does Azathioprine induce endoscopic and histologic healing in pediatric inflammatory bowel disease? A prospective, observational study

Background: The new concept of disease remission for pediatric inflammatory bowel diseases (IBD) implies the achievement of mucosal healing. Aims: We aimed to evaluate endoscopic and histologic healing in children with Ulcerative Colitis (UC) and Crohn's disease (CD) in clinical remission after 52 weeks of Azathioprine. Methods: From December 2012 to July 2015 we prospectively enrolled IBD children starting Azathioprine. Enrolled patients in clinical remission underwent colonoscopy after 52 weeks. Macroscopic assessment was described with Mayo score and the simplified endoscopic score for UC and CD, respectively. For microscopic assessment, an average histology score was used. Data on inflammatory markers and fecal calprotectin were also collected. Results: Fourty-seven patients were included in the analysis. Endoscopic healing was detected in 20/26 (76.9%) UC children and 10/21 (47.6%) CD patients. Median Mayo score and simplified endoscopic score were significantly decreased at week 52 (p < 0.001; p = 0.005). Median average histology score was not significantly different at week 52 in both diseases. Fecal calprotectin was directly correlated with simplified endoscopic score (T0: r = 0.4, p = 0.05; T52: r = 0.5, p = 0.01), but not with Mayo score. No correlation was found between endoscopic and histologic scores. Conclusions: IBD children under Azathioprine reach endoscopic healing, but not histological remission.