Anal fistula is the medical term for an infected tunnel that develops between the skin and the muscular opening at the end of the digestive tract (anus).
Most anal fistulas are the result of an infection that starts in an anal gland. This infection results in an abscess that drains spontaneously or is drained surgically through the skin next to the anus. The fistula then forms a tunnel under the skin and connects with the infected gland.
Surgery is usually needed to treat anal fistula.
Knowing the complete path of an anal fistula is important for effective treatment. The opening of the channel at the skin (external) generally appears as a red, inflamed area that may ooze pus and blood. This external opening is usually easily detected.
Finding the fistula opening in the anus (internal opening) is more complicated. Specialists use the latest technology, including the following:
- Externally applied nitroglycerinto help increase blood flow to the fissure and promote healing and to help relax the anal sphincter. Nitroglycerin is generally considered the medical treatment of choice when other conservative measures fail. Side effects may include headache, which can be severe.
- Topical anesthetic creamssuch as lidocaine hydrochloride (Xylocaine) may be helpful for pain relief.
- Botulinum toxin type A (Botox) injection,to paralyze the anal sphincter muscle and relax spasms.
- Blood pressure medications, such as oral nifedipine (Procardia) or diltiazem (Cardizem) can help relax the anal sphincter. These medications may be taken by mouth or applied externally and may be used when nitroglycerin is not effective or causes significant side effects.
Anal fissures often heal within a few weeks if you take steps to keep your stool soft, such as increasing your intake of fiber and fluids. Soaking in warm water (sitz bath) for 10 to 20 minutes several times a day, especially after bowel movements, can help relax the sphincter and promote healing.
If your symptoms persist, you’ll likely need further treatment.
Your doctor may recommend:
If you have a chronic anal fissure that is resistant to other treatments, or if your symptoms are severe, your doctor may recommend surgery. Doctors usually perform a procedure called lateral internal sphincterotomy (LIS), which involves cutting a small portion of the anal sphincter muscle to reduce spasm and pain, and promote healing.
Studies have found that for chronic fissure, surgery is much more effective than any medical treatment. However, surgery has a small risk of causing stool incontinence.
Treatment of anal fistula depends on the fistula’s location and complexity. The goals are to repair the anal fistula completely to prevent recurrence and to protect the sphincter muscles. Damage to these muscles can lead to faecal incontinence.
The options include:
- Fistulotomy. The surgeon cuts the fistula’s internal opening, scrapes and flushes out the infected tissue, and then flattens the channel and stitches it in place. To treat a more complicated fistula, the surgeon may need to remove some of the channel. Fistulotomy may be done in two stages if a significant amount of sphincter muscle must be cut or if the entire channel can’t be found.
- Advancement rectal flap. The surgeon creates a flap from the rectal wall before removing the fistula’s internal opening. The flap is then used to cover the repair. This procedure can reduce the amount of sphincter muscle that is cut.
- Seton placement. The surgeon places a silk or latex string (seton) into the fistula to help drain the infection.
- Fibrin glue and collagen plug. The surgeon clears the channel and stitches shut the internal opening. Special glue made from a fibrous protein (fibrin) is then injected through the fistula’s external opening. The anal fistula tract also can be sealed with a plug of collagen protein and then closed.
- Ligation of the intersphincteric fistula tract (LIFT). LIFT is a two-stage treatment for more-complex or deep fistulas. LIFT allows the surgeon to access the fistula between the sphincter muscles and avoid cutting them. A seton is first placed into the fistula tract, forcing it to widen over time. Several weeks later, the surgeon removes infected tissue and closes the internal fistula opening.
In cases of complex fistula, more-invasive procedures may be recommended, including:
- Ostomy and stoma. The surgeon creates a temporary opening in the abdomen to divert waste into a collection bag, to allow the anal area time to heal.
- Muscle flap. In very complex anal fistulas, the channel may be filled with healthy muscle tissue from the thigh, labia or buttock.