Parks vs AGA classification for perianal fistula outcomes

What is known

• Parks classifies tracts anatomically (intersphincteric, transsphincteric, suprasphincteric, extrasphincteric; modified to add superficial/submucosal) but does not capture secondary tracts, abscess, or proctitis. ^1–4
• The AGA system divides fistulas into simple vs complex using tract anatomy, number of external openings, and complicating features (abscess, proctitis, stricture, rectovaginal involvement). ^2,5,6
• AGA complexity has prognostic relevance, complex fistulas achieve remission less often and undergo more procedures (median 6 vs 3) than simple fistulas. ^2,7
• Parks is regarded as most useful when combined with internal/external opening location and abscess severity, rather than as a standalone outcome predictor. ⁷

What is unknown / caveats

• No head-to-head study of Parks vs AGA for surgical outcome prediction in the retrieved evidence
• AGA 'complex' category aggregates multiple variables and does not permit individualized treatment stratification
• Retrieved sources are reviews/guidelines, not comparative outcome cohorts
• The excerpts describe the two systems' properties but do not quantify their comparative predictive accuracy for surgical outcomes.

References

1. Pelly T, Anand E, Hanna L, Shakweh E, Joshi S, Lung P, Hart A, Tozer P. Time to classify: a narrative and scoping review of the old and the new classifications of perianal Crohn's disease. Tech Coloproctol. 2025;29(1):123. PMID: 40419817.

2. Lee JL, Yoon YS, Yu CS. Treatment Strategy for Perianal Fistulas in Crohn Disease Patients: The Surgeon's Point of View. Ann Coloproctol. 2021;37(1):5-15. PMID: 33730796.

3. American Gastroenterological Association Clinical Practice C. American Gastroenterological Association medical position statement: perianal Crohn's disease. Gastroenterology. 2003;125(5):1503-7. PMID: 14598267.

4. Gecse K, Khanna R, Stoker J, Jenkins JT, Gabe S, Hahnloser D, D'Haens G. Fistulizing Crohn's disease: Diagnosis and management. United European Gastroenterol J. 2013;1(3):206-13. PMID: 24917961.

5. Lan N, Wu X, Shen B. Stem cell therapy: light in the tunnel for penetrating Crohn's disease. Gastroenterol Rep (Oxf). 2023;11:goac085. PMID: 36974084.

6. Cho WJ, Wong SY. A Guide Through the Tunnel: Updates in the Approach to Classification and Management of Perianal Fistulizing Crohn's Disease. Curr Gastroenterol Rep. 2025;27(1):46. PMID: 40576852.

7. Householder S, Picoraro JA. Diagnosis and Classification of Fistula from Inflammatory Bowel Disease and Inflammatory Bowel Disease-Related Surgery. Gastrointest Endosc Clin N Am. 2022;32(4):631-650. PMID: 36202507.

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Draft, generated by the IBDology RAG and not yet clinician-reviewed. Answers are grounded in the retrieved literature listed above; a high faithfulness score means the answer matches its sources, not that the sources are correct.