Anal Fistula

What is an anal fistula?

An anal fistula is an abnormal connection between the epithelialised surface of the anal canal and usually the perianal skin. Anal fistulae originate from the anal glands which are located between the two layers of the anal sphincters and which drain into the anal canal. If the outlet of these glands becomes blocked, an abscess can form which can eventually point to the skin surface. The tract formed by this process is the fistula.

Here is a short video that show's how anal fistulae develop:

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An anal fistula is most commonly caused by an anal abscess. it can also be caused by conditions that affect the intestines. An abscess is a collection of pus. an anal abscess usually develops after a small glad becomes infected with bacteria. The cause of an abscess is relatively unknown, however, they are more common in people with immune deficiencies. If an anal abscess bursts before it is treated, it can cause an anal fistula to form.

Some other causes include:
  • growth or ulcer
  • a complication of surgery
  • complication of diverticulitis
  • complication of ulcerative colitis
  • complication of Crohn's disease


  • Pain, usually constant but worse when sitting down
  • Skin irritation around the anus (swelling, redness, tenderness)
  • Discharge of pus or blood
  • Fever
  • Constipation or pain when bowel movements occur


The only treatment for anal fistulae is surgery. That being said, the type of surgery will depend on the position of the anal fistula but the options include:
  • Fistulotomy
  • Seton techniques
  • Advancement flap procedures
  • Fibrin glue
  • Bioprosthetic plug

Those affected:

Anal fistulae are a result of the formation of abscesses that go untreated. People with immune deficiencies tend to be more susceptible to forming anal abscesses so they are usually affected. However, anyone can get an anal abscess, and therefore, an anal fistula.


Q. Are antibiotics required to treat this type of infection?

A. Antibiotics alone are a poor alternative to drainage of the infection. Antibiotics are usually only beneficial when used in conjunction with a surgery when the abscess is complicated, however, surgery remains the only effective treatment for anal fistulae.

Q. Is any specific testing necessary to diagnose an abscess or fistula?

A. No. Most anal abscesses or anal fistulae are diagnosed and managed on the basis of clinical findings. Sometimes additional tests suck as MRI, CT scan, or ultrasound can assist in helping guide treatment (i.e. they show where the fistula tunnel is).

Q. What are some signs of an abscess or fistula?

A. A patient with an abscess may have pain, swelling, or redness around the anal area. Fever and chills are common, as well as fatigue. Symptoms are similar for patients with a fistula.

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