The natural history of fistulizing Crohn's disease in Olmsted County, Minnesota.

BACKGROUND & 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.