Pediatric IBD-unclassified is less common than previously reported; Results of an 8-year audit of the EUROKIDS registry

Background: Inflammatory bowel disease-unclassified (IBD-U) is diagnosed in ∼10% of pediatric and adolescent onset IBD patients. The EUROKIDS registry (2004) initiated by the Porto IBD working group of ESPGHAN prospectively monitors diagnostic workup of newly diagnosed pediatric and adolescent onset IBD patients. We aimed to describe diagnostic workup, phenotype, and change of diagnosis over time in pediatric IBD-U patients. Methods: Data were collected on children from 52 centers across 20 European countries and Israel, diagnosed with IBD from May 2005 through November 2013. Full endoscopy plus small bowel radiology was considered complete diagnostic workup. Participating centers reporting IBD-U patients were queried in 2014 for follow-up data. Results: IBD-U was the provisional first diagnosis in 265 of 3461 children (7.7%) (91/158 [58%] with pancolitis; 140 [53%] male), diagnosed more frequently under the age of 10 (median age 12.3 years, 89 [34%] under 10 years). Half (48%) had undergone complete diagnostic workup. Lack of small bowel radiology was the prevailing reason for incomplete workup. As a result of reinvestigations (endoscopy in 54%, radiology in 38%) during a median follow-up of 5.7 years (interquartile range, 2.5-7.8), a change in diagnosis from IBD-U to Crohn's disease (12%) or ulcerative colitis (20%) was reported. Conclusions: Only half of patients reported as IBD-U in EUROKIDS had undergone complete diagnostic workup. Follow-up with reinvestigations resulted in a reduction of IBD-U rate to 5.6%. A diagnosis of IBD-U becomes less likely in case of complete diagnostic workup. Implementation of clear diagnostic criteria will further reduce the rate of IBD-U in the future.