Structured magnetic resonance imaging and endoanal ultrasound anal fistulas reporting template (SMART): An interdisciplinary Delphi consensus

Table 5 Classifications of anal fistulas

	Parks classification[22]	Garg classification[11,12]	St. James University Hospital classification[36]
Grade I	Intersphincteric	Low trans-sphincteric/low or high intersphincteric: Single tract	Intersphincteric linear
Grade II	Transsphincteric	Low trans-sphincteric/low or high intersphincteric: Multiple tracts, horseshoe or associated abscess	Intersphincteric with extension/s or associated abscess
Grade III	Suprasphincteric	IIIA: High trans-sphincteric: Single tract; IIIB: (1) Anterior fistula in a female or any lower; (2) Grade I or II fistula with associated comorbidities1	Trans-sphincteric linear
Grade IV	Extrasphincteric	High trans-sphincteric: Multiple tracts, horseshoe or associated abscess	Trans-sphincteric with extension/s or associated abscess
Grade V		Suprasphincteric or supralevator or extrasphincteric or RIFIL fistula	Supralevator and translevator extension

¹Comorbidities: Crohn’s disease, existing sphincter injury/weakness or post-radiation Low fistula involves ≤ 1/3 and high fistula involves > 1/3 of the sphincters.

RIFIL: Roof of ischiorectal fossa inside levator.