Colonic & Anorectal Fistulas - NIDDK (2024)

What are colonic and anorectal fistulas?

A fistula is an abnormal passageway, 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 the colon to the surface of the skin or to an internal organ, such as the bladder, small intestine, or vagin*.

An anorectal fistula is an abnormal tunnel from the anus or rectumto the surface of the skin around the anus. Women may have rectovagin*l fistulas, which are anorectal fistulas between the anus or rectum and the vagin*.

How common are colonic and anorectal fistulas?

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

Studies conducted in Europe have found that about 1 or 2 in 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 abscessand 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 about 40.13,14

What are the complications of colonic and anorectal fistulas?

Colonic fistula

Colonic fistulas can cause complications such as

  • problems with the fluid and electrolyte balance in your body, such as dehydration or low levels of certain electrolytes
  • malnutrition
  • infections, such as urinary tract infections
  • peritonitis, an infection of the lining of the abdominal cavity
  • abscesses, which are painful, swollen, pus-filled areas caused by infections
  • sepsis, a serious illness that occurs when your body has an overwhelming immune system response to an infection

Anorectal fistula

Anorectal fistulas cause infections and abscesses around the anus, but they rarely cause severe infection. In rare cases, cancer may develop in an anorectal fistula.

What are the symptoms of colonic and anorectal fistulas?

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

Colonic fistula

Symptoms of colonic fistula vary, depending on the location of the fistula. The contents of the colon may 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, stool, and gaspassing

  • through an opening in the skin
  • in the urine
  • through the vagin*

A fistula that connects the colon to another part of the intestinesmay cause symptoms such as

  • diarrhea
  • pain in the abdomen
  • weight loss

In some cases, colonic 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 rectovagin*l fistula may cause symptoms such as the passage of stool or gas through the vagin*.

What causes colonic and anorectal fistulas?

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

Colonic fistula

The most common cause of colonic fistulas is abdominal surgery. Diseases that cause inflammation of the GI tract, such Crohn’s disease and diverticular disease, can also cause fistulas to form. Other causes include cancer, radiation therapy, and trauma or injury to the abdomen.

Colonic & Anorectal Fistulas - NIDDK (1)

Anorectal fistula

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

Certain health problems may 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 may also cause anorectal fistulas.

How do doctors diagnose colonic and anorectal fistulas?

Doctors diagnose colonic 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 colonic 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 may perform a digital rectal exam and may perform an anoscopy or a proctoscopy to view the inside of the anus and rectum.

Imaging tests

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

  • ultrasound, which uses sound waves to create an image of your organs
  • lower GI series, which uses x-rays and a chalky liquid called barium to view your large intestine
  • computed tomography (CT) scans, which use a combination of x-raysand computer technology to create images
  • magnetic resonance imaging (MRI), which takes pictures of your body’s internal organs and soft tissues without using x-rays
  • fistulography, which involves taking x-rays after injecting contrast media into a fistula to help it show up more clearly on the x-rays

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 vagin*, doctors may order additional tests to examine these organs.

How do doctors treat colonic and anorectal fistulas?

Colonic fistula

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

  • give you fluids and electrolytes
  • give you nutritional support, which may include total parenteral nutrition (TPN), which is intravenous (IV) nutrition, or enteral nutrition, in which 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 not likely to close on its own, doctors perform surgery to close the fistula.

Anorectal fistula

Doctors typically treat anorectal fistulas with surgery. Most anorectal fistulas won’t close on their own without surgery, but some rectovagin*l fistulas may close on their own. If you have a rectovagin*l fistula, your doctor may recommend delaying surgery to see if the fistula will close.

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.


Colonic & Anorectal Fistulas - NIDDK (2024)


What is colonic and anorectal fistula? ›

How common are colonic and anorectal fistulas? Colonic fistulas are rare and may occur as a complication of surgery or of a condition such as diverticulitis, Crohn's disease, or cancer link. Studies conducted in Europe have found that about 1 or 2 in every 10,000 people have anorectal fistulas.

How serious is a colon fistula? ›

Possible Complications

Fistulas may result in malnutrition and dehydration, depending on their location in the intestine. They may also cause skin problems and infection.

What causes anorectal fistulas? ›

Risk factors for an anal fistula include:
  • Previously drained anal abscess.
  • Crohn's disease or other inflammatory bowel disease.
  • Trauma to the anal area.
  • Infections of the anal area.
  • Surgery or radiation for treatment of anal cancer.
Sep 1, 2022

What is the most common anorectal fistula? ›

Intersphincteric Fistulas:

Inevitably, as most abscesses develop in the place between these sphincters, the most common type is an intersphincteric fistula. That is one that crosses the internal sphincter and then has a tract to the outside of the anus leading.

What are the symptoms of a colonic fistula? ›

Patients with gastrocolic fistulas may present with symptoms of abdominal pain, weight loss, and feculent belching. Enterovesical and colovesical fistulas are easier to diagnose in patients who present with symptoms of pneumaturia, fecaluria, and recurrent urinary tract infections.

Can you poop with a fistula? ›

Complications of a rectovagin*l fistula may include: Uncontrolled loss of stool, called fecal incontinence. Problems keeping the perineum clean. Recurrent vagin*l or urinary tract infections.

Does a fistula always mean Crohn's? ›

Purpose: Though perianal fistulas are commonly seen in patients with Crohn's disease, they can also be seen in patients without inflammatory bowel disease.

Do fistulas hurt when you poop? ›

Symptoms of an anal fistula

It can cause intense pain and swelling around the anus. This pain gets worse with bowel movements. Sometimes there's discharge from the opening around the anus. You may also have a fever and bleeding around the area.

Can a fistula be seen during a colonoscopy? ›

Colonoscopy is not particularly accurate for the detection of fistula. However, colonoscopy is sensitive for the detection of an underlying colonic malignancy, especially colonic malignancies associated with diverticular disease. The use of MRI in diagnosing a fistula has been poorly investigated.

Is a fistula like a hemorrhoid? ›

Since both these conditions affect the same part of the body, they are often confused for being the same. However, that is far from true. Though they both impact the anus, fistula and piles are two very distinct medical conditions.

What is the life expectancy of a fistula patient? ›

The overall median survival of AVFs was 3.1 years (range 0.1–12.3 years), whereas the 3-year and 5-year survival rates were 51.0% (95% confidence interval 45.3%–56.8%) and 34.5% (95% confidence interval 29.0%–40.0%), respectively.

What is worse fissure or fistula? ›

Fissure is a medical term referring to the tearing of the skin, whereas fistula is abnormal tube-like connections or passages between organs. Generally, fissures can get cured in a few days or few weeks, often without even needing any treatment. They are not known to cause much complication.

What will happen if a fistula is left untreated? ›

These are more difficult to surgically repair. In addition, recurrent fistulas are not only painful, but can compromise your immune system. Delaying treatment can cause the development of more abscesses. An untreated fistula can lead to systemic infections which can spread to other parts of the body.

Where is the most common location of a fistula? ›

Fistula Definition: A fistula is an abnormal connection or passageway that connects two organs or vessels that do not usually connect. They can develop anywhere between an intestine and the skin, between the vagin* and the rectum, and other places. The most common location for a fistula is around the anus.

How do you repair a colonic fistula? ›

A minimally invasive procedure, endoscopic fistula closure is used to repair a hole or opening (fistula) with the help of an endoscope — a flexible tubelike imaging instrument. An endoscope helps a doctor look inside the body, locate the fistula and close it.

How long does a colon fistula take to heal? ›

The expected time period for spontaneous closure, if it is to occur at all, varies with the anatomic location of the fistula. Fistulas from the esophagus and duodenum are expected to heal in two to four weeks. Colonic fistulas may heal in 30 to 40 days. Small bowel fistulas may take at least 40 to 60 days.

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