Submucosal fistulae pass superficially beneath the submucosa and do not cross either sphincter muscle. Differential diagnosis
Other conditions in which infected perianal "holes" or openings may include pilonidal cyst. Treatment
There are several stages to treating an anal fistula:
Definitive treatment of A fistula aims to stop it recurring. Treatment depends on where the fistula lies, and which parts of the internal and external anal sphincters it crosses. Lay-open of fistula-in-ano – this option involves an operation to cut the fistula open. Once the fistula has been laid open it will be packed on a daily basis for a short period of time to ensure that the wound heals from the inside out. This option leaves behind a scar, and depending on the position of the fistula in relation to the sphincter muscle, can cause problems with incontinence. This option is not suitable for fistulae that cross the entire internal and external anal sphincter. Cutting seton – if the fistula is in a high position and it passes through a significant portion of the sphincter muscle, a cutting seton (from the Latin seta, "bristle") may be used. This involves inserting a thin tube through the fistula tract and tying the ends together outside of the body. The seton is tightened over time, gradually cutting through the sphincter muscle and healing as it goes. This option minimizes scarring but can cause incontinence in a small number of cases, mainly of flatus.
Epidemiology
A literature review published in 2018 showed an incidence as high as 21 people per 100,000. "Anal fistulas are 2–6 times more prevalent in males than females, with the condition occurring most frequently in patients in their 30s and 40s." References


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