Health Library

Anal Fistula

Definition

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Causes

Anal fistulas are caused by damaged tissue. They are often linked to cysts or infections of anal glands. Fistulas can also be caused by sores, ulcers, or other injuries.

Sometimes there is no known cause of an anal fistula.

Risk Factors

Anal fistulas are more common in men. However, women also get them. They are also more common in those 30 to 50 years old. Other things that may raise the risk are:

Symptoms

An anal fistula may cause:

  • Lasting rectal pain, swelling, soreness, or redness
  • A mass in the anal area that moves
  • Discharge from the anal opening
  • Fever or chills

Diagnosis

The doctor will ask about symptoms and health history. A physical exam will be done. The doctor will examine the skin around the anus. This may be enough to make the diagnosis.

Sometimes the doctor wants to do more tests, such as:

  • Anoscopy—exam of the anal canal with a scope
  • Probe—a thin, small probe is inserted into the anal skin to see if a channel is present
  • Imaging tests to view the area, such as:
    • CT scan
    • MRI
    • Fistulography—an x-ray to look at the fistula

Treatment

The first goal is to treat any infection or health problem that caused the fistula. This may include draining the swollen area.

A fistula is repaired with surgery. Sometimes surgery is done in stages. It depends on how severe the fistula is and where it is located.

Surgery may include:

  • Fistulotomy—A trench is created in the fistula. This helps it heal from the inside out.
  • Sealant or plug—A substance is used to fill in the fistula. Both ends of the fistula are closed off. This allows it to heal.
  • Endorectal flap—A flap is created to expose the internal opening of the fistula. The fistula is stitched shut and the flap is put back in place.
  • Ligation of intersphincteric fistula tract (LIFT)—The inner fistula is tied off. Any infected tissue in the anal canal is removed. The fistula is stitched at the outer opening.
  • Fistulectomy—The fistula is completely removed—this is rare.

Some procedures may affect muscles that open and close the anus. Depending on the treatment, this may make it hard to hold stool (poop) sometimes.

Medicine may be given to:

  • Ease pain
  • Treat infection
  • Soften stool (poop)—to decrease straining

Prevention

The risk of anal fistula may be lowered by:

  • Carefully cleaning and treating anal/rectal wounds
  • Managing certain health conditions

Resources

American College of Gastroenterology
http://gi.org

American Society of Colon and Rectal Surgeons
https://www.fascrs.org

Canadian Resources

Canadian Association of Gastroenterology
https://www.cag-acg.org

Health Canada
https://www.canada.ca

References

Abscess and fistula expanded information American Society of Colon and Rectal Surgeons website. Available at: https://fascrs.org/patients/diseases-and-conditions/a-z/abscess-and-fistula-expanded-information. July 26, 2021.

Anal fistula. John Hopkins Medicine website. Available at: https://www.hopkinsmedicine.org/health/conditions-and-diseases/anal-fistula. Accessed July 26, 2021.

Fistula-in-ano and anorectal abscess. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/fistula-in-ano-and-anorectal-abscess. Accessed July 26, 2021.

Garg P. Anal fistula associated with anal fissure. Tech Coloproctol. 2020 Jul;24(7):785.