S1480 Characterization of the Clinical Course and Magnetic Resonance Imaging Findings in Isolated Perianal Crohn’s Disease: A Case Series

Introduction: Crohn’s disease (CD) can manifest with perianal symptoms, including abscess/fistulae, which result in significant morbidity. These perianal manifestations of disease can occur despite a complete absence of luminal CD, thus being termed Isolated Perianal CD (IpCD). The natural history and radiographic description of Isolated perianal (IpCD) remains largely uncharacterized. We report a case series of patients diagnosed with IpCD at a tertiary care center, where the aim is to characterize the incidence of IpCD, the delay in CD diagnosis, and the typical imaging findings and clinical course of the IpCD phenotype. Methods: We conducted a retrospective chart review on patients with ipCD and applied descriptive statistics to characterize the incidence, clinical course, and MRI findings of the disease. Results: We identified 19 patients with IpCD between 2017-24 for an incidence of 1.4%. All patients had normal initial colonoscopies and small bowel imaging, and all patients were initially managed by general surgery. The mean time from symptom onset to diagnosis was 3.6 ± 2.9 years. During this period 12/19 (63%) required antibiotics, and 16/19 (84%) required surgical management in addition to 13/19 (68%) presenting to the emergency department and 12/19 (63%) requiring hospitalization for perianal related symptoms. Only 7/19 (37%) of patients were started on anti-TNF biologics within the mean follow-up period of 3.4 ± 2.5 years. 7/19 (37%) of patients reached clinical remission in the study and only 1 developed microscopic findings of luminal CD. For imaging findings, 18/19 patients (95%) had at ≥1 fistula of which 18/19 (95%) were complex with a median maximal St. James classification of 4 (IQR = 2). Conclusion: There is a significant delay between symptom onset and diagnosis of ipCD, with this time characterized by complex perianal fistulas requiring frequent surgical interventions, antibiotics, healthcare expenditure and overall morbidity. Earlier identification of these patients and their starting on gold-standard anti-TNF therapy should be a priority, and further work should focus on the development of prediction models to identify patients at high risk of having IpCD.