Indeterminate colitis: a significant subgroup of pediatric IBD.

Background: Indeterminate colitis (IC) is a subgroup of inflammatory bowel disease (IBD) that cannot be characterized as either ulcerative colitis (UC) or Crohn's disease (CD). Our aims are to determine the prevalence of IC in our pediatric patient population and to describe its clinical presentation, natural history,and disease distribution.

Methods: We performed a retrospective database analysis of all children diagnosed with IBD at the Johns Hopkins Children's IBD Center between 1996 and 2001. Patient demographics, including age, sex, and age at disease onset, were tallied. Disease distribution was identified on the basis of a review of all endoscopic, colonoscopic, histopathological, and radiological records. All of the patients were followed up clinically to determine the extent of disease progression on the basis of the initial diagnosis of IC.

Results: Among 250 children registered in the database, 127 (50.8%) had a diagnosis of CD, 49 (19.6%) had UC, and 74(29.6%) had IC. Patients with IC had a significantly younger mean +/- SEM age (9.53 +/- 4.8 years) at diagnosis compared with patients with CD (12.4 +/- 3.8 years; P < 0.001) but not compared with patients with UC (7.41 +/- 3.5 years). Among the patients with IC, 59 (79.7%) had a pancolitis at diagnosis, and the remaining 15 had left-sided disease that progressed to a pancolitis within a mean of 6 years. Twenty-five patients (33.7%) with an initial diagnosis of IC were reclassified to either CD or UC after a median follow-up of 1.9 years (range 0.6-4.5 years). Forty-nine patients (66.2%) maintained their diagnosis of IC after a mean follow-up of 7 years (SEM 2.5 years).

Conclusions: IC is a distinct pediatric subgroup of IBD with a prevalence that is higher than that observed in adults. Children with IC have an early age of disease onset and a disease that rapidly progresses to pancolitis. Longitudinal studies are needed to determine the clinical implications of this pediatric IBD subgroup.