Disease characteristics, outcomes, and poor prognostic factors of perianal fistula in Korean patients with Crohn’s disease: a multicenter, retrospective observational study

Background/Aims A high proportion (39%-50%) of Korean patients with Crohn's disease (CD) suffer from perianal fistula, and real-world data on clinical practice remain limited. This study aimed to identify characteristics of perianal fistulizing CD (pfCD), treatment patterns, disease outcomes, and factors associated with poor prognosis in clinical practice in Korea. Methods This was a multicenter, retrospective, observational study using chart reviews and clinical assessment of adult patients with pfCD from 15 medical centers. Patients were aged ≥ 19 years and had been treated for a newly diagnosed perianal fistula after January 1, 2011, with ≥ 1 year of follow-up. At enrollment, patient demographics, characteristics, treatments, and clinical outcomes were assessed. Results Between September 2022 and August 2023, 487 patients met the inclusion criteria. Median age at initial diagnosis of perianal fistula was 21.7 years; 65.1% of patients had complex pfCD and 26.5% had multiple fistulas. Most patients (62.4%) had fistula-related surgical intervention (minor: 90.8%, 276/304; major: 22.4%, 68/304). Fistula recurrence was common (36.8%); median time to recurrence was 0.9 years (range, 0.01-10.8 years). Complications of perianal fistula including abscess (hazard ratio [HR], 1.67) and stricture (HR, 3.23), and fistula-related surgical intervention during the recurrence period (HR, 1.50) were positively associated and use of biologics (HR, 0.38) was negatively associated with recurrence events. Conclusions This study highlights the high burden of disease, with most patients receiving multiple treatments and over one-third experiencing fistula recurrence. Biologics may be associated with lower risk of fistula recurrences.