Abstract Background Perianal fistulas are a common manifestation of Crohn’s disease (CD) and occur in ∼10% of patients with ileal pouch-anal anastomosis (IPAA). It is unclear whether these fistulas share the same pathophysiology and respond similarly to medical therapy Aims To compare the anatomy and complexity of IPAA-related fistulas (IPAA-RF) with perianal Crohn’s disease (PFCD) fistulas Methods A retrospective comparative cohort study was conducted at The Ottawa Hospital (01/01/2004–01/01/2025). Adults (17 years) with IPAA were matched 1:1 to PFCD patients by age and sex. Perianal, rectovaginal and rectogenitourinary fistulas were included; luminal, pouch-body fistulas and fistulas within six months of ileostomy takedown were excluded. Patients were identified by chart review using ICD-10 codes (Crohn’s, Ulcerative colitis). Fistula anatomy was classified by Park’s (anal sphincter) and complexity defined per AGA criteria. Results We identified 66 IPAA patients and 66 matched PFCD controls. Age at diagnosis was similar (IPAA 38±11vs.PFCD 37±12 years). Smoking was more common in PFCD(40%vs.12%). PFCD patients were more likely to have multi-organ fistulas (p = 0.0006), whereas rectovaginal fistulas were more frequent in IPAA (38%vs.24%,p=0.009). There were no significant differences in anal sphincter involvement per Park’s classification. Overall rates of complex fistulas were comparable (78%vs.68%), but branching tracts were more frequent in PFCD(31%vs.12%). Conclusions In this single-center cohort, IPAA-RF differed from PFCD, being more often rectovaginal, while PFCD showed greater multi-organ involvement and branching tracts. Although overall complexity was similar, these anatomic differences may influence management. Further studies are warranted to assess long-term outcomes in IPAA-RF. A286 Table 1: Fistula Characteristics Funding Agencies None
Kandel et al. (2026) studied this question.