740 Prevalence of Anorectal Fistula's in Crohn's Disease: A National, Population-Based Study

Abstract

INTRODUCTION: Perianal fistulizing disease is associated with significant morbidity and impairment in the quality of life in patients with Crohn's disease (CD). However, there is limited national level data on the prevalence of anorectal fistulas (AF) in CD. Similarly, there is a paucity of data on the prevalence of CD in patients with an initial presentation of an AF. METHODS: The aim of this study was to investigate the prevalence of AF in patients with CD, and to estimate the prevalence of CD in patients with an initial presentation for AF in a large, national database. Data was collected from a commercial database (Explorys Inc, Cleveland, OH) that provided electronic health records from 27 major integrated US healthcare systems from 1999 to June 2019. In this dataset, we identified all CD and AF based on Systemized Nomenclature of Medicine - Clinical Terms “Crohn's disease” and “Anorectal fistula.” We conducted searches with CD as the index event prior to the development of AF, and searches with AF as the index event prior to CD to identify the temporal relationship between CD and AF. We determined the prevalence of the second diagnosis at 30 days, 3 months, 6 months, 1 year, 3 years, and 5 years after the index event. RESULTS: Of the 63,036,150 individuals in the database, we identified 187, 070 patients with CD. Of these, 7,160 patients had a had a diagnosis of an AF after the diagnosis of CD, with an overall prevalence of 3.27%. The prevalence rate of AF in Caucasians, African Americans and Asians with CD was 3.79%, 5.08%, and 2.92% respectively. The prevalence of AF in CD varies with age (Figure 1) and the highest prevalence of AF was in the 35-49 year age groups. The majority (96%) of anorectal fistulas were identified within the first 30 days of CD diagnosis. Among the 63,036,150 individuals in the database, we identified 45,060 patients with anorectal fistulas. In this cohort, the prevalence of CD was 15.9%. The majority of cases of CD were diagnosed within 30 days of diagnosis of AF (6,630 out of 7,160, or 93% of CD cases). The overall prevalence ratio of CD in those with AF compared to those without AF was 55.6 [95% CI 54.4 to 56.9, P < 0.0001]. CONCLUSION: In this large, cross sectional population database study, we determined that nearly 3.3% of CD patients have perianal fistula. Furthermore, 16% of all perianal fistulas are associated with a diagnosis of CD. Therefore, it is reasonable to screen all patients who are diagnosed with anorectal fistulas for CD.