OBJECTIVES: Perianal fistula (PAF) is the most disabling complications of Crohn’s disease (CD). As there is limited information about the journey of CD patients with PAF in Japan, this study was performed to describe the diagnosis patterns of PAF associated with CD contemplating the size of facilities.

METHODS: A retrospective longitudinal cohort study was conducted, in which all subjects with a diagnosis of PAF and/or CD between January 2005 to August 2019 were determined by ICD-10 codes. A descriptive analysis was conducted. The data source was an anonymized claims database of Japanese company employees and their family members. Patients diagnosed with PAF between October 2013 and August 2019 after diagnosis of CD were defined as pattern A. Patients diagnosed with CD during the same period after diagnosis of PAF were defined as pattern B. Facilities in which the initial diagnosis of either PAF or CD was made were categorized into 3 groups of size depending on the number of beds (small: ≤199, medium: 200-499, and large: ≥500).

RESULTS: 1,135 CD patients and 12,456 PAF patients were considered during the study period (dataset population: 7,438,470, as of January 2020 and 269 patients were counted as CD-associated PAF. Of these patients, 42 and 184 patients belonged to Pattern A and B, respectively. In the remaining patients, PAF and CD diagnosis were made in the same month. The rate of patients in small, medium and large-scale facilities were 26, 31, and 43% in pattern A, respectively, and 82, 8, and 10% in pattern B, respectively.

CONCLUSIONS: This study shows that most of the patients from the pattern B were diagnosed as PAF in small-sized facilities as opposed to pattern A, suggesting that the certified coloproctological small-sized facilities play an important role in the diagnosis of PAF with CD in Japan.

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