DEVELOPMENT OF CROHN'S DISEASE IN PATIENT PRESENTING WITH COMPLEX PERIANAL FISTULA TO A TERTIARY MEDICAL CARE CENTER

Abstract BACKGROUND Approximately 20% of patients with Crohn’s disease (CD) will develop a perianal fistula (PAF), most of which are complex fistulas1-4. Studies have shown that 4-5% of patients with CD present with perianal fistula without luminal disease, termed isolated perianal Crohn’s disease4,5,6. However, little is known about the natural history of isolated complex PAF (iPAF). We therefore aimed to evaluate the clinical course of patients who presented with iPAF including describing those who subsequently developed luminal CD. METHODS We performed a retrospective cohort study of patients seen within the Mount Sinai Health System (New York) with an ICD-10 diagnosis code for PAF between 7/22/2008 and 7/22/2022. Medical record review was conducted to identify patients with complex PAF who did not have evidence of luminal disease and had > 6 months of follow-up (Table 1). Luminal disease was defined as any evidence of ulcers, erosions, or strictures on endoscopic or video capsule exam or MRE with evidence of inflammation consistent with luminal CD. Demographics, comorbidities, imaging, endoscopy, surgeries, hospitalizations and medication data were collected. Descriptive and univariate analyses were performed. Complicated disease course was defined as a composite of any major CD-related surgery, PAF/IBD-related hospitalization or biologic use. RESULTS Among 887 patients with PAF, 62.2% (n=552) patients underwent luminal evaluation, of whom 80 patients (14.5%) were found to have no luminal disease (Table 1). Of these, 57 patients had >6 months of follow-up with 22.8% (n=13) going on to develop luminal disease. Luminal CD was diagnosed at a mean time of 4.2 (SD=3.8) years after iPAF presentation. Compared to patients who developed luminal CD, patients with solely iPAF were less likely to be <30 years old at PAF diagnosis (p=0.0225) or have concomitant autoimmune conditions (p=0.046) (Table 2). Patients with iPAF were less likely to have >2 fistulas (p=0.002) or have CD/PAF-related hospitalization (29.5% vs 61.5%, p =0.0356) compared to those who developed luminal CD (Table 2). Patients with iPAF were significantly less likely to have a complicated disease course than those who later developed luminal CD (2.3% vs 30.8%, p=0.007). CONCLUSION We observed that approximately 1 in 4 patients who presented with iPAF went on to develop luminal CD. Patients who went on to develop luminal CD were more likely to be <30 at PAF diagnosis, have concomitant autoimmune conditions and were more likely to have IBD-related adverse outcomes. The majority of patients with iPAF did not experience a complicated disease course and may represent a specific sub-phenotype of CD.