An anal fistula is an abnormal communication between the anal canal and another surface, usually the skin around the anus.
Following drainage of perianal abscess, about 50% heal and 50% will develop a fistula, presenting usually with a discharge (chronic and/or intermittent) from a perianal opening. The abscess is caused in 90% of cases because of infection of anal glands (cryptoglandular therory) which number 10 to 15 in humans.
Fortunately, most anal fistula are simple and do not have much anal muscle below them, allowing them to be “laid open”, known as a fistulotomy.
If the fistula has a lot of muscle below it and there is concern about incontinence in association with a fistulotomy, a seton (derived from the Latin setae=bristle) may be placed. Setons may be loose, cutting or fibrosing, and are usually made from thin silastic rubber.
Complex anal fistula include those where incontinence is of concern if a fistulotomy was performed, meaning about 30 to 50% of anal muscle below, anterior (vaginal side) fistula in a female, and those with multiple tracts and those associated with Crohn’s disease.
Various treatments are used for complex fistula because of imperfect results for all of them, and are best discussed with your doctor. They include setons, fibrin glue, anal fistula plug, mucosal advancement flap, rectal advancement flap, LIFT procedure and BioLIFT procedure.