An anal fistula is when a tunnel forms from the anal canal to the skin or organs near it. If left untreated, fistulas can cause problems such as infections.
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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.
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:
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
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
- Fistulography—an x-ray to look at the fistula
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
The risk of anal fistula may be lowered by:
- Carefully cleaning and treating anal/rectal wounds
- Managing certain health conditions
American College of Gastroenterology
American Society of Colon and Rectal Surgeons
Canadian Association of Gastroenterology
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.
Last reviewed July 2021 by EBSCO Medical Review Board Dan Ostrovsky, MD Last Updated: 7/26/2021