Time trends in the epidemiology and outcome of perianal fistulizing Crohn's disease in a population-based cohort.

OBJECTIVE: Perianal disease is a debilitating condition that frequently occurs in Crohn's disease (CD) patients. It is currently unknown whether its incidence has changed in the era of frequent immunomodulator use and biological availability. We studied the incidence and outcome of perianal and rectovaginal fistulas over the past two decades in our population-based Inflammatory Bowel Disease South-Limburg cohort.

PATIENTS AND METHODS: All 1162 CD patients registered in the Inflammatory Bowel Disease South-Limburg registry were included. The cumulative probabilities of developing a perianal and rectovaginal fistula were compared between three eras distinguished by the year of CD diagnosis: 1991-1998, 1999-2005 and 2006-2011. Second, clinical risk factors and the risk of fistula recurrence were determined.

RESULTS: The cumulative 5-year perianal fistula rate was 14.1% in the 1991-1998 era, 10.4% in the 1999-2005 era and 10.3% in the 2006-2011 era, P=0.70. Colonic disease was associated with an increased risk of developing perianal disease, whereas older age was associated with a decreased risk (both P<0.01). Over time, more patients were exposed to immunomodulators or biologicals before fistula diagnosis (18.5 vs. 32.1 vs. 52.1%, respectively, P=0.02) and started biological therapy thereafter (18.6 vs. 34.1 vs. 54.0%, respectively, P<0.01). The cumulative 5-year perianal fistula recurrence rate was not significantly different between eras (19.5 vs. 25.5 vs. 33.1%, P=0.28). In contrast, the cumulative 5-year rectovaginal rate attenuated from 5.7% (the 1991-2005 era) to 1.7% (the 2006-2011 era), P=0.01.

CONCLUSION: Over the past two decades, the risk of developing a perianal fistula was stable, as well as its recurrence rate, underlining the lasting need for improving treatment strategies for this invalidating condition.