High complex anal fistula managed by the modified transanal opening of the intersphincteric space via the inter-sphincteric approach: A case report

Figure 1 Representative images showing the surgical procedure for anal fistulas; the red shaded area indicates the surgical wound, and the green arrow denotes the surgical approach and operating path. A: Drainage from the intersphincteric infection contaminates the anal glands and perianal space through the glandular branches, creating an anal fistula and intersphincteric abscess; B: Fistulectomy involves the surgical removal of fistula tissues and surrounding muscles, fat and connective tissues, resulting in a large wound area; C: Transanal opening of the intersphincteric space (TROPIS) involves the identification of the internal opening by injecting methylene blue or using a probe, followed by opening the fistula tract in the intersphincteric plane through the transanal route, resecting the lower part of the internal sphincter and scraping out the remaining branching fistulas; D: Modified TROPIS involves the widening of the intersphincteric plane through the transanal route and the identification of the internal opening easily and precisely, followed by drainage of the fistulas passing through the intersphincteric plane and tunnel-like fistulectomy of fistulas located lateral to the external sphincter. Branching fistulas with larger curvatures located lateral to the external sphincter are scraped out.