Indeterminate colitis: clinical spectrum of disease.

A diagnosis of indeterminate colitis (IC) is based on endoscopic, histologic, and radiologic findings when the criteria for either Crohn's colitis or ulcerative colitis (UC) cannot be definitively established. Population-based studies have demonstrated that the average annual incidence of IC ranges 1.6 to 2.4/100,000 versus 7.3 to 13.6/100,000 for UC. At the time of initial diagnosis of inflammatory bowel disease, up to 10% to 15% of patients will be diagnosed as having IC. Over time, greater than 50% of patients with IC will be given a diagnosis of UC or Crohn's, with the majority being diagnosed with UC. Therefore, approximately 4% to 5% of all patients with inflammatory bowel disease will be left with the diagnosis of IC. Clinically, patients with IC seem to have a more severe course with a greater chance of colectomy and pouch failure. No studies have been undertaken to determine the optimum treatment regimen for IC. Recent studies have shown that patients with IC are still appropriate candidates for ileal pouch anal anastomosis. In conclusion, the current data support the premise that IC may be a separate entity, but future studies will have to focus on the genotypic and phenotypic characterization of these patients.