What are colon and anorectal fistulas?

A fistula is an abnormal passage or tunnel in the body. An internal fistula is an abnormal tunnel between two internal organs. An external fistula is an abnormal tunnel between an internal organ and the outside of the body.

A colonic fistula is an abnormal tunnel from colon to the surface of the skin or to an internal organ, such as bladder, the small intestineor vagina.

An anorectal fistula is an abnormal tunnel from anus or rectum to the surface of the skin around the anus. Women can have rectovaginal fistulas, which are anorectal fistulas between the anus or rectum and the vagina.

How common are colon and anorectal fistulas?

Colonic fistulas are rare and can occur as a complication of surgery or from a condition such as diverticulitis, Crohn’s diseaseor cancer.

Studies conducted in Europe have found that about 1 or 2 out of every 10,000 people have anorectal fistulas.¹³ Anyone can get an anorectal fistula, which usually starts as an infection in a gland inside the anus. Anorectal fistulas are more likely to occur in people who have had an anorectal abscess and in people with Crohn’s disease.

Anorectal fistulas are more common in men than in women. While anorectal fistulas can occur in people of any age, the average age of people with anorectal fistulas is around 40.^13,14

What are the complications of colon and anorectal fistulas?

Colon fistula

Colon fistulas can cause complications such as

Anorectal fistula

Anorectal fistulas cause infections and abscesses around the anus, but they rarely cause serious infection. In rare cases, cancer can develop into an anorectal fistula.

What are the symptoms of colon and anorectal fistulas?

You should see a doctor if you have symptoms of a colonic or anorectal fistula.

Colon fistula

Colon fistula symptoms vary depending on the location of the fistula. The contents of the large intestine can enter the fistula and pass to the other end, which may be in the skin or in an internal organ.

Symptoms of colonic fistula may include fluid, fecesand gas passes

• through an opening in the skin
• in urine
• through the vagina

A fistula that connects the large intestine to another part of the intestines can cause symptoms such as

In some cases, colon fistulas do not cause symptoms.

Anorectal fistula

Symptoms of an anorectal fistula may include

• drainage of pus from an opening in the skin around the anus
• swelling and pain near the anus that may come and go, sometimes with redness or fever
• anal pain

In women, a rectovaginal fistula can cause symptoms such as passage of stool or gas through the vagina.

What causes colon and anorectal fistulas?

Most colon and anorectal fistulas are acquired, meaning they are not present at birth and develop at some point in a person’s life.

Colon fistula

The most common cause of colonic fistulas is abdominal surgery. Diseases that cause inflammation of the gastrointestinal tract, such as Crohn’s disease and diverticular diseasecan also cause fistula formation. Other causes include cancer, radiation therapyand trauma or injury to the abdomen.

Anorectal fistula

Anorectal abscesses, caused by infections of the anal glands, are the most common cause of anorectal fistulas.

Certain health problems can also cause anorectal fistulas, including Crohn’s disease, cancer and some infections such as tuberculosis and HIV. Damage to the anorectal area due to surgery, childbirth, injury, or radiation therapy can also cause anorectal fistulas.

How do doctors diagnose colon and anorectal fistulas?

Doctors diagnose colon and anorectal fistulas based on symptoms and medical history, a physical exam, and imaging tests.

Medical history

Your doctor will ask about your symptoms and history of conditions that may cause fistulas, such as abdominal surgery, Crohn’s disease, diverticular disease, radiation therapy, or injury.

Physical exam

Your doctor will check for tenderness or pain in your abdomen and may listen to sounds inside your abdomen using a stethoscope. Your doctor will examine any opening in your skin to determine if you may have an external colon fistula.

To check for an anorectal fistula, your doctor will check the skin around your anus for abnormal openings, pain, and signs of inflammation or infection. Your doctor can perform one digital rectal examination and can perform a anoscopy or a proctoscopy to see the inside of the anus and rectum.

Imaging tests

Doctors may use several different imaging tests to diagnose or investigate colonic or anorectal fistulas. The type of test depends on the suspected location of the fistula. Tests may include

Doctors may order additional tests to check for complications or to diagnose conditions that can cause fistulas, such as Crohn’s disease or cancer. If a fistula connects to an internal organ, such as the bladder, small intestine, or vagina, doctors may order additional tests to examine those organs.

How do doctors treat colon and anorectal fistulas?

Colon fistula

Some colon fistulas will close on their own without surgery. Your doctor can only treat or prevent complications to help the fistula heal. Depending on your needs, your doctor may

• give you fluids and electrolytes
• give you nutritional supportwhich may include total parenteral nutrition (TPN) which is intravenous (IV) nutrition or enteral nutrition, where you receive liquid food through a tube placed in your nose, stomach, or small intestine
• prescribe antibiotics and drain any abscesses to treat infection
• protect your skin from the fluid draining from the fistula if you have an external fistula

If a fistula is unlikely to close on its own, doctors perform surgery to close the fistula.

Anorectal fistula

Doctors typically treat anorectal fistulas with surgery. Most anorectal fistulas do not close on their own without surgery, but some rectovaginal fistulas can close on their own. If you have a rectovaginal fistula, your doctor may recommend delaying surgery to see if the fistula closes.

If you have an anorectal fistula with an abscess, your doctor will drain the abscess to treat the infection. In some cases, doctors may prescribe antibiotics to treat the infection.

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