Isolated Perianal Fistulas: When and How Should I Investigate for Inflammatory Bowel Disease?

Key Takeaways: • Approximately, 5–10% of all perianal fistulizing Crohn’s disease (PFCD) patients will have isolated PFCD. High or complex tracts, multiple internal openings, chronicity, and refractoriness to treatment—along with patient factors—should raise suspicion for PFCD (isolated or not). • A negative initial luminal evaluation does not exclude CD — surveillance is key. Up to 25% of patients presenting initially with isolated complex fistulas develop luminal CD over time (median 2.5 years). Periodic reassessment with imaging, endoscopy, and symptom monitoring is critical to avoid missed or delayed diagnosis. • Diagnosis and management of isolated PFCD requires a multidisciplinary, patient‑centered approach. TOpClass criteria offer practical diagnostic guidance using clinical, radiologic, and histologic features. For patients with significant symptoms and complex isolated PFCD, anti-TNF therapy may be considered, though evidence is limited and optimal duration remains unclear.