Magnetic resonance imaging findings in patients with initial manifestations of perianal fistulas

BACKGROUND: Crohn's disease (CD) is a serious cause of perianal disease and the incidence is increasing in Saudi Arabia. MR imaging may document specific features that may help to foresee Crohn's disease in patients making an initial presentation. OBJECTIVE: Present MR imaging findings of perianal fistulas in patients making an initial presentation. DESIGN: Retrospective, observational. SETTING: Radiology clinic in in Dhahran. PATIENTS AND METHODS: All previously undiagnosed and untreated patients who presented for the first time to the outpatient clinics from September 2015-2018 with perianal fistulas were retrospectively evaluated. Previously diagnosed CD patients, post-surgical or intervention cases were excluded. Fistulas were categorized as low or high anal, simple or complex, and were graded per St. James University Hospital Classification. Imaging was interpreted by two experienced readers based on the Van Assche score. MAIN OUTCOME MEASURES: Fistula features on MR imaging and diagnosis of CD. SAMPLE SIZE: 171 patients. RESULTS: Of 171 patients, 139 (81.3%) were males with mean age of 37.2 (12.7) years; the 32 females had a mean age of 35.8 (10.6) years. Twenty-one patients (12.3%) had CD. Fourteen (40.4%) patients with complex fistulas had CD in comparison to only 5 (4.8%) simple fistula patients (P=.0005). More than half of patients with complex and high anal fistulas had CD (P=.0005). Females were more affected than males (P=.0005). CONCLUSION: Complex or high anal fistula on MR imaging may be the initial presentation of CD and warrant further work up to establish the diagnosis. LIMITATIONS: Retrospective, small sample, single center, and short duration study.