A fistula rarely heals by itself, and surgery is often required, according to the UK's National Health Service. The specific type of surgery depends on the position of the fistula and whether it is classified as simple or complex.
Used in 85 to 95 percent of cases, a fistulotomy is the most common type of anal fistula surgery. During this procedure, the surgeon cuts open the whole length of the fistula, flushes out the contents and flattens it out. After one to two months, the fistula heals into a flat scar, explains the NHS.
In some cases, the surgeon may decide to use a seton, a piece of surgical thread left in the fistula tract to keep the tract open. This allows the fistula to drain properly over the course of several months. A seton is usually considered when the patient is at high risk of developing incontinence because the fistula crosses the sphincter muscles, notes the NHS. A bioprosthetic plug serves the same purpose, blocking the internal opening of the fistula but allowing it to drain through the external opening.
An advancement flap procedure is required for a complex fistula; this involves removing a piece of tissue from the rectum or from the skin around the anus and attaching it to the internal opening of the fistula. Fibrin glue is currently the only nonsurgical option for treating an anal fistula, according to the NHS, but long-term results from this method are not promising.