An anal fistula is a tunnel, or a tract, that runs from an internal opening on the anal wall and exits the skin near the anus. The disease is caused by infection of one of the numerous mucus glands circumferentially ringing the anus that usually make mucus for lubrication. The condition can form into an abscess. Half of these abscesses may turn into an anal fistula as they gradually burrow their way out through the perianal skin. The outer end of the fistula is visible as a small opening in the skin near the anus.
Symptom
Anal fistulas can cause the following unpleasant symptoms:
- Fluid oozing out or bloody drainage from an opening near the anus
- Recurrent anal abscesses
- Bloody, fetid purulent drainage from an opening near the anus.
- Irritated skin around the anus because of drainage
- Pain during bowel movements
- Fever, chills, and fatigue
Consult your doctor immediately if these symptoms are present.
Cause
The most common cause of anal fistula is an obstructed anal gland forming an anal abscess. Other causes include:
- Inflammatory bowel disease (IBD) such as Crohn's disease
- Radiation exposure during the treatment of cancer
- Trauma
- Sexually transmitted diseases
- Tuberculosis
- Diverticulitis, a disease of the colon.
- Cancer
Diagnosis
The doctor will examine the skin around the anus to look for a skin opening of a small tunnel. If found, the doctor will determine how deep it is and in what direction it is going by palpating for the presence of a fibrous tract leading away from the opening. Some patients may have drainage from the external opening.
However, fistula opening cannot be seen with the naked eye in some patients in the usual perianal skin location. In this case, you will be advised to undergo some additional tests as follows:
- Your doctor may use an anoscope to inspect the inside of your anus and rectum.
- You may be asked to undergo an ultrasound and MRI of the anal area.
- In some cases, examination in the operating room under anesthesia may be necessary.
Patients with complex anal fistula may need further tests, especially if they have symptoms suggestive of Crohn’s disease because statistically, 25 % of people with Crohn’s disease develop fistulas. As a result, some anal fistula patients may be asked to do a blood test, X-ray, and colonoscopy.
Treatment
Most patients with anal fistula require surgery to cure the fistula. The surgery should be designed to circumvent significant damage to anal sphincter muscles that can cause "fecal incontinence," an uncontrollable bowel movement with stool leaking out of the rectum at an unwanted time.
In the case where there is no or little sphincter muscle overlying the fistulous tunnel, fistulotomy in which all skin and muscle over the tunnel is cut to lay open the entire length of the tract would be done, allowing it to heal from the bottom up and close the tract during the healing process.
In a more complex case, a special drain called a seton would be inserted into the fistula tract for at least 6 weeks for drainage. With the seton use, some follow-up operations are almost always needed, including:
- Fistulotomy
- A flap advancement procedure wherein a flap of tissue from the lining of the rectum is raised and moved to cover the internal opening of the tract.
- A “LIFT” procedure to open up the anal skin, separate sphincter muscle fibers, core out the fistulous tract and then suture both cut ends of the tract closed.
Stem cell injection into the fistulous tract is a new treatment for fistula associated with Crohn's disease. A colorectal surgeon will discuss all options with the patient before the surgery. Typically, the patients can go home on the day of surgery, as it is a day surgery procedure. However, those with extensive and deep tunnels may require a short stay in the hospital. In addition, multi-stage operations may be necessary for some patients with complex, high fistula types to avoid loss of sphincter control and fecal incontinence.
