Incidence, Paris classification, and follow-up in a nationwide incident cohort of pediatric patients with inflammatory bowel disease.

OBJECTIVES The aim of the study was to evaluate the incidence, baseline disease characteristics, and disease location based on the Paris classification in pediatric inflammatory bowel disease (IBD) in the Hungarian nationwide inception cohort. In addition, 1-year follow-up with therapy was analyzed. METHODS From January 1, 2007 to December 31, 2009, newly diagnosed pediatric patients with IBD were prospectively registered. Twenty-seven pediatric gastroenterology centers participated in the data collection ensuring the data from the whole country. Newly diagnosed patients with IBD younger than 18 years were reported. Disease location was classified according to the Paris classification. RESULTS A total of 420 patients were identified. The incidence rate of pediatric IBD was 7.48/10⁵ (95% confidence interval [CI] 6.34/10⁵-8.83/10⁵). The incidence for Crohn disease (CD) was 4.72/10⁵ (95% CI 3.82-5.79), for ulcerative colitis (UC) 2.32/10⁵ (95% CI 1.71-3.09), and for IBD-unclassified 0.45/10⁵ (95% CI 0.22-0.84). Most common location in CD was L3 (58.7%); typical upper gastrointestinal abnormalities (ulcer, erosion and aphthous lesion) were observed in 29.9%. Extensive colitis in patients with UC (E4, proximal to hepatic flexure) was the most common disease phenotype (57%), whereas only 5% of children had proctitis. A total of 18.6% of patients had ever severe disease (S1). Frequency of azathioprine administration at diagnosis was 29.5% in patients with CD, and this rate increased to 54.6% (130/238) at 1-year follow-up. In UC, only 3.3% received azathioprine initially, and this rate elevated to 22.5% (25/111). Use of corticosteroid decreased from 50% to 15.3% in patients with UC. Rate of bowel resection in patients with CD during the first year of follow-up was 5%. CONCLUSIONS The incidence of pediatric IBD in Hungary was among the higher range reported. This is the first large, nationwide incident cohort analyzed according to the Paris classification, which is a useful tool to determine the characteristic pediatric CD phenotype