The Impact of Integrating Pelvic Magnetic Resonance Imaging at Diagnosis on Early Detection of Perianal Crohn's Disease in Pediatrics.

Introduction: Perianal Crohn's disease (CD) can be a severe manifestation of pediatric CD. Earlier detection may alter outcomes. The aim of this study was to determine if performing pelvic magnetic resonance imaging (MRI) on newly diagnosed pediatric patients with CD would identify asymptomatic perianal CD and lead to earlier biologic use and less perianal surgery.

Methods: Patients were prospectively enrolled into the Edmonton Pediatric Inflammatory Bowel Disease Clinic registry (baseline pelvic MRI since 2018). A retrospective review (2018-2023) was performed. A blinded radiologist re-read the positive MRIs using St. James and Parks criteria.

Results: One hundred thirty-nine patients were included (median age 13 [interquartile range 11-16, range 6-18]). Overall, 19% (n = 27/139) had subclinical perianal disease (MR+/asymptomatic [ASx]). For patients who were both asymptomatic and had a normal perianal examination (n = 86/139, 62%), their subclinical perianal disease rate was similar at 20% (n = 17/86). Compared with MR-/ASx, MR+/ASx patients had a relative risk of 1.40 (95% confidence interval [CI] 1.18-1.68) and 1.32 (95% CI 1.17-1.52) of starting a biologic at 6 and 12 months, respectively. MR+/Sx needed the most and earliest perianal surgery, but MR+/ASx also had higher rates and faster time to perianal surgery than MR-/ASx ( P = 0.02). Perianal side branch fistula was a predictor of surgery (odds ratio 107.6, [95% CI 16.9-2,178] P < 0.0001).

Discussion: One in 5 newly diagnosed pediatric patients with CD had subclinical perianal disease, even when having a normal perianal physical examination. These patients needed more and earlier perianal surgery and had higher biologic use despite their perianal disease being subclinical. Adding routine MR imaging at the time of pediatric CD diagnosis may help inform treatment decisions and improve these outcomes.