Factors Associated with Fistulizing Crohn's Disease in Children at Diagnosis: A Cross-Sectional Study.

Background: Perianal manifestations are common at diagnosis of Crohn's Disease and include perianal fistulas, abscesses, fissures, and inflammatory anal skin tags. Perianal fistulizing Crohn's disease (PFCD), involving fistulas and abscesses, is associated with a poor prognosis in children.This study aimed to identify the factors associated with PFCD at diagnosis. Secondary aims were to: assess factors associated with the severity of PFCD according to the Van Assche score, characterize the prevalence of perianal Crohn's disease in a Canadian cohort, and evaluate its management at diagnosis.

Methods: We collected data from patients aged 4-18 years diagnosed with Crohn's disease between 2009 and 2021 at our IBD center who underwent perineal magnetic resonance imaging within three months of diagnosis. Perianal Crohn's disease was assessed clinically and through MRI results.

Results: Among 489 patients (57.9% male, median age 13.8 years), 229 (46.8%) had perianal Crohn's disease. Perianal fistulizing Crohn's disease was identified in 115 patients (23.5%), including 13.0% without any clinical signs. The median Van Assche score was 13.0 in patients with PFCD versus 2.0 in those without. Male sex, granulomas on intestinal biopsies, and anal fissures were associated with both the presence and increased severity of PFCD.

Conclusion: This study emphasizes the importance of performing perianal MRI early at the diagnosis as occult perianal fistulizing Crohn's disease may be discovered. Male sex, granulomas on intestinal biopsies and anal fissures were associated both with the presence of PFCD and increased severity.