Key Points about Anal Fistula

  • Anal fistulas are infected channels that develop when an anal gland becomes blocked. About 50% of patients with an abscess infection that doesn’t heal properly get an anal fistula.
  • Pain, swelling and sometimes rectal bleeding can be symptoms of anal fistulas.
  • During a physical exam of the rectal area, a fistula is usually easy to spot.


An anal fistula is a small channel that connects a gland inside the anal canal to the outside skin near the anus. Sometimes these glands get clogged and become infected. Once infected, it creates an abscess, or a cavity filled with pus. After the pus drains from the abscess, it can leave behind a narrow channel or tunnel.

I feel like we could mention the openings internal/external here if you wanted. You mention “identify internal openings” in the diagnosis section, but we don’t mention what that is. Wikipedia says: “Internal opening in the anal canal and external opening in the skin near the anus.”

An anal fistula usually occurs due to a past or current anal abscess. About 50% of patients with an abscess infection that doesn’t heal properly get an anal fistula.

Anal fistula causes

In most cases, an anal fistula starts with an infection in an anal gland. Other conditions that can cause an anal fistula include:

  • Cancer
  • Crohn’s disease(an inflammatory disease in the digestive tract)
  • Diabetes
  • Diverticulitis(an infection of pouches that form in the intestine)
  • Radiation therapy to treat the anal area
  • Sexually transmitted diseases
  • Trauma to the anal area
  • Tuberculosis

Anal fistula risk factors

The glands around your anus produce fluid and when they get blocked, an infection can occur. When this happens, you’re at risk of developing an anal fistula. Although rare, there are other risk factors, including:

  • Crohn's disease
  • Diverticulitis
  • Sexually transmitted diseases
  • Other conditions such as tuberculosis or cancer
  • Trauma
  • History of radiation therapy

Anal fistula symptoms

Pain, swelling and sometimes rectal bleeding can be symptoms of anal fistulas. Other symptoms include:

  • Bloody pus that comes from an opening in your skin near your anus
  • Feelings of fatigue
  • Fever and chills
  • Frequent anal abscesses
  • Irritation around the anal skin
  • Pain with bowel movements
  • Soreness to the touch in the anal area

Anal fistulas diagnosis

A fistula is usually easy to spot during a physical exam of the rectal area. However, sometimes there are no visible signs except redness. If this is the case, you may need to see a specialist.

A specialist can perform additional tests such as an internal rectal exam, an endoanal ultrasound or pelvic MRI to map the fistula tract and identify internal openings.

After a diagnosis, the doctor might perform other tests to make sure there aren’t any serious conditions.

Anal fistulas treatment

Treatment for anal fistulas can include non-surgical and surgical options. If an abscess is present, it’s important to have it drained. Once drained, a fistula may persist and some will experience recurring pain, swelling and drainage.

An anal fistula is almost always removed through surgery and if an abscess is present, both often can be removed at the same time. If the fistula can be treated without surgery, then the doctor may prescribe medicine or warm baths to help reduce pain and discomfort.

When to seek care

If you are experiencing pain, discomfort or bleeding in the anal area, please talk to your doctor about your concerns. Your primary care doctor may suggest seeing a gastroenterologist for more specialized treatment.

Find a gastroenterologist near you

Bon Secours locations that can treat you