It is an abnormal track (a fine tube) that develops between the inner lining of the anus and the skin near the anus. It is the result of an untreated abscess. The usual symptoms include pus drainage from the perianal skin, itching and irritation. The treatment is surgical and consists of eliminating the track by laying it open or by excising it. When a fistula lies either too close to the sphincter or goes through it, a thread of nylon or other non-absorbable material is placed through the fistula track (seton) and tied outside the body. The seton is tightened over time, gradually cutting through the sphincter muscle(like the cheese-wire) and healing as it goes by scar tissue.