Anal Fistula

An anal fistula is a small infected tract that has an internal opening in the anal canal and an external opening in the skin near the anus. Most anal fistulas are the result of an infection that starts in an anal gland. This infection results in an abscess. The abscess may be drained surgically through the skin next to the anus or it may drain spontaneously. The fistula then forms a tunnel under the skin and connects with the infected gland that has not healed completely. It occurs especially when there have been recurring anal abscesses.

It is important to treat the fistula to reduce the risk of infection and relieve symptoms. Surgery is usually needed to treat an anal fistula.

What are the symptoms?

Patients with anal fistula experience symptoms such as:

  • Fever
  • Severe pain in the anal region, especially while sitting down
  • Skin irritation around the anus
  • Swelling and redness in the anal region
  • Pus or bloody discharge while passing stools

The external opening of the fistula is generally easily located and usually red, inflamed, oozes pus and is sometimes mixed with blood. Locating the internal opening can sometimes be a challenge and it is important to be able to find the entire fistula for the treatment to be effective.
Sometimes the fistula can actually be felt but locating its visual path often requires various aids such as:

  • Fistula probe. An instrument specially designed to be inserted through a fistula
  • Anoscope. A small instrument to view the anal canal. If a fistula is potentially complicated or in an unusual place additional diagnostic tools may be used:
  • Diluted methylene blue dye that is injected into the fistula
  • Fistulography: Contrast solution is injected the fistula and x rays are taken.
  • MRI

It is important to also rule out other disorders such as ulcerative colitis or Crohn’s disease with flexible sigmoidoscopy (to view the lining of the rectum and sigmoid colon) or colonoscopy (to examine the entire colon or large intestine).

Anal Fistula Treatment

Treatment needs to be careful to reduce the risk of damage to the anal sphincter muscles. The choice of surgery will depend on the fistula’s location and complexity, and the strength of the patient’s sphincter muscles. Treatment must be tailored to the patient’s condition.


In a fistulotomy the surgeon first probes to find the fistula’s internal opening. Then the tract is cut open and is scraped and the sides are stitched to the sides of the incision in order to lay open the fistula.
The surgery may be performed in more than one stage if a large amount of muscle must be cut. The surgery may need to be repeated if the entire tract 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.

Ligation of the intersphincteric fistula tract (LIFT) is done for complex anal fistula

Seton Placement: A seton is a thin silicone string (similar to an elastic band) which is inserted into the fistula tract. This allows the fistula to drain and heal from the inside out over several weeks. Or the presence of the seton may create scar tissue around part of the sphincter muscle before cutting it with a knife.

Fibrin Glue or Collagen plug

Rather than cutting the fistula open, in some cases, fibrin glue, made from plasma protein, may be used to seal up and heal a fistula. The glue is injected through the external opening after clearing the tract and stitching the internal opening closed. A plug of collagen protein may also be used to seal and close the fistula tract.

How do you prepare for the surgery?

Your doctor will ask you to:

  • take laxatives to empty your stomach the day before surgery
  • avoid solid food from the day before surgery
  • avoid smoking
  • On the day of surgery you will have a simple enema to wash out the colon.
  • Your anaesthetist will meet you to assess you clinically and review your reports.

Since you will be able to go home on the same day of surgery, have a friend or family member be available to take you home. You should not drive as there may be slight residual effects of anaesthesia.

What can you expect post-surgery?

Following your fistula surgery, your surgeon will recommend soaking the affected area in a warm bath and taking stool softeners or laxatives for a week. For the pain or discomfort in the area after surgery, you will be prescribed pain killers. Most fistulas respond well to surgical treatment.