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

Table 6 Definitions of anal fistulas

Terms	Definitions
Primary fistula	Main fistulous tract with the internal opening at the dentate line (occasionally the internal opening can be lower or higher than the dentate line)
Single fistula	Fistula without branching (extensions/ramifications)
Multiple fistulas	More than one primary fistula with their corresponding internal openings
Branching fistula	Fistula with branches (extensions/ramifications)
Low fistula[12,25]	Fistula that involves ≤ 1/3 of the external anal sphincter
High fistula[12,25]	Fistula that involves > 1/3 of the external anal sphincter
Simple fistula[12,25]	Low intersphincteric or low transsphincteric primary fistula (Garg grades I/II)[11,12] at low risk of incontinence or recurrence
Complex fistula[12,25]	High inter- or trans-sphincteric, suprasphincteric, extrasphincteric fistula (Garg grades III–V)[11,12], ano/rectovaginal fistula, any fistula in Crohn’s disease, a fistula postradiotherapy, anterior fistula in a female, recurrent fistula, fistulas with multiple tracts, pre-existing sphincter injuries at high risk of postoperative incontinence or recurrence