Anal fistulas are common conditions that require specialized care by a surgeon well trained in the management of anorectal problems. An anal fistula is a tunnel covered with rectal and skin lining called epithelium that presents either as an acute infection or recurrent pain and passage of purulent secretion. Patients presenting with recurrent abscesses are often suspected to have a fistula as the underlying cause. Most fistulas are believed to be related to an infection in an anorectal mucus secreting gland that spreads and forms a tunnel lined with granulation or inflammatory tissue that fails to close after the infection has cleared. But fistulas at times can also be associated with other diseases like Crohn’s disease, pilonidal disease, hydradenitis, trauma or cancer. They are more commonly found in males than in females and are present more often in the third to fifth decade of life.
Proper examination of an anal fistula involves evaluation of the perianal skin by carefully feeling the area with the use of specialized probes. Some imaging techniques like MRI and Endoanal Ultrasound are useful sometimes in the evaluation of complex and recurrent anal fistulas.
Most fistulas are preceded by an infectious process called abscess, but most abscesses are not associated with fistulas. If a fistula is found during the drainage of an abscess, it is often better to drain the abscess and place a loose rubber band, known as a Seton, through the tunnel (to keep it open and avoid a recurrence of the infection) until the inflammation has resolved. This allows better assessment of the fistula to determine the best treatment for it. In some instances simple fistulas involving little or no sphincter muscle can be treated at the same time as the abscess.
The best way of getting an anal fistula to heal is called Fistulotomy. It consists of laying open the tissues over the fistula, removing its lining and allowing it to heal on its own (also called healing by secondary intention). More often than not the muscles tasked with keeping the anal orifice closed (called sphincters) are involved in the fistula. If a significant amount of these muscles must be cut to treat the fistula, the patient may develop incontinence. In those cases the use of a less effective, but function preserving sphincter sparing technique is preferred.
There is wide variety of sphincter sparing procedures available, results may vary widely from one study to another likely due to several factors including patient population differences, variability of fistula classification, inadequate follow up, surgeon preference and skills. Some of the most common sphincter sparing procedures performed are Advancement Flaps which consist on mobilization tissues to close the internal orifice. A LIFT procedure involves accessing the fistulous tract between the sphincter muscles, then it is divided and ligated. Cutting Setons are strings passed through the tract around the sphincter muscles, then the seton is slowly tightened over several weeks to allow for the slow division of the muscle, preventing its ends from springing apart which is often cumbersome and a painful process. Bioprosthetic Plugs can be placed in the fistulous tract to induce healing, this techniques comes to replace the use of Fibrin Glue. The use of Fistulotomy with Immediate Reconstruction of the muscle and Fistulectomy are less commonly used. The simplest method of managing a fistula with sphincter preservation is a Permanent Loose Seton, which preserves continence and prevents most infections but it is not well tolerated by most patients. There are multiple variations of these procedures and their use depends on the particular characteristics of each patient.