Background: Most incidence studies of ulcerative colitis (UC) and Crohn disease (CD) have dealt with adults and there are have been few population-based prospective studies of the incidence of inflammatory bowel disease (IBD) in children. The aim of this study was to determine the incidence after re-evaluation of the diagnosis of UC and CD in childhood and adolescence in a prospective population-based survey.
Methods: From 1 January 1990 to 31 December 1993, all newly diagnosed patients with UC and CD under the age of 16 years were registered. On 1 January 1992 there were 174,482 children in the study population. The diagnosis was based on internationally accepted criteria and all clinical data were reviewed by two gastroenterologists independently of each other. All patients were subjected to a second evaluation 1 year after inclusion in the study. Patients initially diagnosed as indeterminate colitis (IND) were also reassessed.
Results: A total of 14 cases of UC, 13 cases of CD and 2 cases of IND were registered during the study period. At re-evaluation of the two patients diagnosed as IND, one was reclassified as having UC and one as having CD. This yielded a mean annual incidence of 2.14 (95% CI 1.20-3.54) per 100,000 for UC and 2.00 (95% CI 1.10-3.36) per 100,000 for CD. The male:female ratio in UC was 4.0 and 1.8 in CD. Median time interval from onset of symptoms to diagnosis was 4 months for UC and 5 months for CD. A high proportion of the children with UC (80%; 12/15) had extensive colitis. Four patients with CD had a first-degree relative with IBD.
Conclusion: This study does not support an increased incidence of paediatric CD over the past decade. The incidence of paediatric UC seems to have remained stable over the past 30 years. In the CD group, we find a high incidence of IBD in first-degree relatives.