Perianal fistula is an abnormal tract that breaks through the skin around the anus. It can form when anal glands are infected and have abscess. It serves as a passageway for the pus to drain to the skin’s surface. Drainage of pus through the abnormal tract will continue as long as the infection persists.

The condition is often treated with surgery. Its goal is to close the abnormal tract while minimising damage to the sphincter muscles. These muscles are responsible for opening and closing the anus. Any damage to these muscles increases the risk of bowel incontinence.

The prognosis for patients with fistula is very good after surgery. But the procedure does not guarantee that the condition will not occur again in the future. In around 7-21% of cases, the abnormal tract recurs months or years after treatment. The risk of recurrence depends on the complexity and location of the abnormal tract.

Causes of Condition

The condition occurs when bacteria or stool become trapped in small glands just inside the anus. It is a common complication of Crohn’s disease. This condition is marked by the chronic inflammation of the gastrointestinal (GI) tract. It can also occur when pressure causes pockets of tissue to bulge inside the large intestine. These sacs can cause infection if they rupture. Other causes include cancer and trauma to the anus or rectum. Patients with tuberculosis and STDs also have an increased risk of the condition.

Key Symptoms

Perianal abscess causes pain. The pain can be so intense that patients may find it difficult to sit still. This symptom is often relieved when the abscess is drained. Perianal fistulas, on the other hand, do not cause pain but they can be itchy. They can continuously drain pus as long as there’s an infection. Their external opening is often inflamed and red in colour. Patients also have a bump in the anal area that does not heal.

Who to See and Types of Treatments Available

The condition can be diagnosed by a general doctor. For treatment, patients are referred to a general or colorectal surgeon.

A simple rectal examination is often enough for doctors to make a diagnosis. But they often need to perform tests to trace the internal opening of the tract. These can be done by:

  • Inserting a scope into the anus to assess the anal and rectal areas. This procedure is called anoscopy.

  • Injecting a contrast solution to the tract. The patient then undergoes an x-ray. This provides the doctor with an image that shows the origin of the fistula. Magnetic resonance imaging (MRI) may also be used. This test provides more detailed information than x-rays.

Treatment of the condition depends on many factors. The most important is the location of the fistula. Doctors have to ensure that the patient’s sphincter muscles will not be damaged in the process. Otherwise, patients may suffer from bowel incontinence.

The condition can be treated with fibrin glue and bioprosthetic plugs. Fibrin glue is injected into the fistula so it will close and heal. Bioprosthetic plugs, on the other hand, can be used to block the internal opening of the tract. This prevents pus from entering the tract, allowing it to dry and heal. These treatment methods provide short-term symptoms relief. However, they often do not cure the condition. They are used if surgery is not an option. This is the case if the tract runs through the sphincter muscles. Surgeons may elect not to surgically treat it to avoid permanent damage to the said muscles.

Surgery to treat the condition is called fistulotomy. In this procedure, the surgeon cuts open the entire tract. This causes it to dry and heal as a flat scar. Another option is the use of seton. This surgical thread is inserted and left inside the tract. It keeps the tract open, allowing the pus to drain completely. Seton threads may then be used to cut through the tract slowly.

Advancement rectal flap is also another option. For this procedure, the tract is cut open. The surgeon will then cut a flap into the rectal wall. After removing the internal opening of the tract, the flap is stitched back down. This option minimises the amount of sphincter muscle that needs to be cut during the procedure.

Patients are often allowed to go home after the procedure. They are advised to soak the treated area in warm baths several times a day. This helps speed up the healing process. They are also advised to eat soft foods to prevent constipation. Doctors also prescribe medications to treat any pain or discomfort caused by the surgery.

Recovery time takes between two to four weeks. But many patients are able to go back to work a week after the procedure. They may be advised to make a follow-up with their doctor to ensure that their wound is healing well. Doctors also want to make sure that no complications have developed.

References:

  • Wald A, Bharucha AE, Cosman BC, Whitehead WE. ACG clinical guideline: management of benign anorectal disorders. Am J Gastroenterol. 2014 Aug. 109(8):1141-57; (Quiz) 1058.

  • Hamalainen KP, Sainio AP. Incidence of fistulas after drainage of acute anorectal abscesses. Dis Colon Rectum. 1998 Nov. 41(11):1357-61; discussion 1361-2.

  • Perry WB, Dykes SL, Buie WD, Rafferty JF. Practice parameters for the management of anal fissures (3rd revision). Dis Colon Rectum. 2010 Aug. 53(8):1110-5

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