Background and Aims: Little is known about the cumulative incidence and natural history of fistulas in Crohn's disease in the community. Methods: The medical records of all Olmsted County, Minnesota residents who were diagnosed with Crohn's disease from 1970 to 1993 and who developed a fistula were abstracted for clinical features and outcomes. Six patients denied research authorization. The cumulative incidence of fistula from time of diagnosis was estimated by using the Kaplan-Meier product-limit method. Results: At least 1 fistula occurred in 59 patients (35%), including 33 patients (20%) who developed perianal fistulas. Twenty-six (46%) developed a fistula before or at the time of formal diagnosis. Assuming that the 9 patients with fistula before Crohn's disease diagnosis were instead simultaneous diagnoses, the cumulative risk of any fistula was 33% after 10 years and was 50% after 20 years (perianal, 21% after 10 years and 26% after 20 years). At least 1 recurrent fistula occurred in 20 patients (34%). Most fistulizing episodes (83%) required operations, most of which were minor. However, 11 perianal fistulizing episodes (23%) resulted in bowel resection. Conclusions: Fistulas in Crohn's disease were common in the community. In contrast to referral-based studies, only 34% of patients developed recurrent fistulas. Surgical treatment was frequently required.
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