Burden of perianal disease in Crohn's disease: Accelerating medical therapy and high rates of perianal surgery over the last four decades - Results from a population-based study over four decades.

Background: Few population-based studies have investigated the prevalence and disease course of perianal manifestation in Crohn's disease.

Aims: To analyse the prevalence and outcomes of perianal Crohn's disease including medical therapies and need for perianal surgery, over different therapeutic eras based on the time of diagnosis; cohort A (1977-1995), cohort B (1996-2008), and cohort C (2009-2018) METHODS: Patient inclusion lasted between 1977 and 2018. We followed patients prospectively, and regularly reviewed both in-hospital and outpatient records. We defined a perianal surgical procedure as any perianal incision and excision, fistulotomy, or abscess drainage.

Results: We included 946 incident patients. Perianal disease at diagnosis was present in 17.4% (n = 165) of the total cohort, with a declining prevalence in cohorts A/B/C, respectively (24.7%/18.5%/13.2%; p = 0.001). By the end of follow-up, an additional 9.3% (n = 88) of the total cohort developed perianal disease. Cumulative immunosuppressive and biologic exposure increased over time; biologic use was higher in patients with perianal disease [pLog Rank < 0.001]. The overall rate of perianal surgery was 44.7% (113/253), with a probability of 28.3% (95% CI: 25.4-31.2) after 10 years, 41.0% (95% CI: 37.5-44.5) after 20 years, and 64.1% (95% CI: 59-69.2) after 30 years. There was no statistically significant difference in the probability of first perianal surgery among cohorts A/B/C [Log Rank = 0.594].

Conclusions: The burden of perianal disease and perianal surgery rates were high in this cohort. Therapeutic strategy was accelerated in patients with perianal Crohn's over time with higher exposure to immunosuppressives and biologics. Surgical management of perianal disease remained unchanged amongst the cohorts.