Perianal magnetic resonance imaging findings and their potential impact on outcome in children with perianal fistulizing Crohn disease

Background: Children with perianal fistulizing Crohn disease require intensive medical management but also have a higher risk for subsequent surgical interventions. Objective: We performed a retrospective study to identify patient factors and perianal anatomical features by pelvic MR that are associated with surgical interventions in these children. Materials and methods: We included children with Crohn disease and perianal fistula who underwent pelvic MR with available, archived images and collected demographic, clinical and laboratory data. Radiologists reviewed pelvic MR exams and identified Park classification and additional anatomical features of perianal fistulas, including fistula branching, horseshoe ramifications, abscess, inflammatory mass, supralevator extension, anal sphincter damage, proctitis and posterior anal space involvement. We performed univariate and subsequent multivariate analysis to determine features associated with subsequent surgical intervention. Results: Ninety-nine children with Crohn disease underwent pelvic MR. In this cohort, 69 children had no surgical interventions prior to baseline MRI, with subsequent median clinical follow-up of 5.5 years. Univariate analysis demonstrated that branching (P=0.009), supralevator extension (P=0.015) and anal sphincter damage (P=0.031) were significantly associated with subsequent surgical intervention. Age at baseline MRI was also associated with intervention (hazard ratio [HR] every 5 years: 2.13; 95% confidence interval [CI]: 1.18–3.83; P=0.012). A multivariable model identified only fistula branching (HR: 2.31; 95% CI: 1.28–4.15; P=0.005) and age (HR: 5.18; CI: 1.57–17.14; P=0.007) as independent predictors of subsequent surgery. No demographic, clinical or laboratory parameter predicted subsequent surgical intervention. Conclusion: Age and anatomical MR features indicating fistula complexity (branching, supralevator extension) and sphincter damage confer a higher risk of subsequent surgical intervention in children with perianal Crohn disease.