The natural history of pediatric-onset IBD-unclassified and prediction of Crohn's disease reclassification: a 27-year study.

Objectives: A definitive diagnosis of Crohn's disease (CD) or ulcerative colitis (UC) in patients who were initially diagnosed as inflammatory bowel disease-unclassified (IBDU) remains challenging. Our aims were to describe the natural history of pediatric-onset IBDU patients during prolonged period of follow up and to identify associated predictors for CD reclassification among them. Materials and methods: In this retrospective single center study, out of 723 patients with pediatric onset IBD, we identified 53 patients (7.3%) diagnosed with IBDU at the Schneider Children's Medical Center of Israel between 1986 and 2013. Potential predictors for CD reclassification including age at diagnosis, gender, clinical manifestations, disease extent and laboratory findings were assessed. Results: The median follow-up was 6.8 (6.7) years. Reclassification to CD was observed in 24/53 (45%) of patients. The median interval from diagnosis to CD reclassification was 9.4 years. In 58% of these patients, CD reclassification occurred within 5 years from diagnosis. Multivariate Cox models showed that familial history of CD and hypoalbuminemia at diagnosis were significantly associated with CD reclassification (HR 11.3, p=.02 and HR 5.3, p = .03, respectively). All other assessed clinical, laboratory and endoscopic parameters did not serve as predictors for CD reclassification later on. Conclusions: In our cohort, a substantial high proportion of pediatric onset IBDU patients were later re-diagnosed as CD. Only a family history of CD and hypoalbuminemia could predict reclassification among IBDU patients.