Objectives: Few prospective population-based studies have been carried out on the incidence of inflammatory bowel disease (IBD). In a population-based study of pediatric IBD in southeastern Norway, patients <16 years at the time of diagnosis were followed up prospectively. The study reports on changes in diagnosis and clinical outcome 5 years after diagnosis.
Methods: From 1990 to 1993 new cases of IBD were registered in a population of 174,482 children aged less than 16 years. The patients' diagnoses were systematically evaluated 1 year after diagnosis and the patients were followed up clinically for up to 5 years after diagnosis.
Results: Sixteen cases of Crohn's disease (CD), 14 cases of ulcerative colitis (UC) and 3 cases of indeterminate colitis (IND) were initially registered. After 1 year IND were reclassified as UC (n=2) or CD (n=1). Altogether, 18% (6/33) had their diagnosis changed during the 5 years of follow-up, which yielded a mean annual incidence of 2.7/100,000 for CD and 2.0/100,000 for UC. Of the children with CD, more than 80% had relapses during the 5-year period, and 6 of 18 had surgery. Two-thirds of the children with UC had relapses during the 5-year period, and 3 patients underwent colectomy.
Conclusions: An incidence of 4.7/100,000 is comparable to that found in most other studies made in Europe. The relationship between UC and CD in children was found to differ from that in the adult population. One of 5 patients had their diagnosis changed during the follow-up period. Pediatric UC seems to have a more serious course of disease than in the adult IBD population, which may be explained by the higher risk of pancolitis at diagnosis.