The goals of treatment of a fistula-in-ano are the elimination of sepsis and of the fistula tract, the prevention of recurrence, and the preservation of continence. A fistula-in-ano always traverses or passes through a portion of the internal anal sphincter and usually some, if not all, of the external anal sphincter.
Treatment of an anal fistula requires surgery in an operating room under general or regional anesthesia. The majority of fistulae can be managed by simply laying open the fistula tract. This involves dividing the overlying tissue, which includes a portion of the sphincter complex. The chronic inflammatory tissue is removed and the wound is allowed to heal secondarily by scar tissue formation.
For fistulas that involve the internal anal sphincter or only a small portion of the external anal sphincter there is a small risk of incontinence postoperatively. The greater the amount of external sphincter traversed by the fistula, the greater the risk of postoperative incontinence after the lay-open technique.
Alternative treatments are available for persons in whom the risk of incontinence would be too great using this technique. The most commonly used method is the use of a seton.
A seton is a thread passed around the fistula tract. It can be made of many different materials including silk or nylon suture, rubber, or plastic. Setons can be used in many different ways. They can act as drains to prevent recurrent infections. They can mark the site of a fistula tract to permit it to be divided in stages, thus reducing the chance of postoperative incontinence. Finally, they can be intermittently tightened to slowly cut through the sphincter muscles. The rationale here is that healing and scarring occurs as the seton cuts through the muscle, preventing division of the muscle all at once.
For a patient with a fistula that is not amenable to either the lay-open technique or treatment with a seton, there are a number of more complex surgical procedures available. The most commonly used is the creation of a flap of tissue in the anal canal to cover the internal opening in combination with drainage of the external opening and fistula tract.