Fistulas are a common complication of Crohn’s disease. These are atypical tunnels that form on the intestinal walls or other organs.

People with Crohn’s disease may experience fistulas forming in different parts of the intestines with another organ, such as the bladder, or through to the skin surface.

Individuals with fistulas may experience undesirable side effects, such as:

  • diarrhea
  • pain
  • discomfort

An anal fistula is the most common type of fistula. Symptoms include a tender swelling or lump around the anus that may drain and pain that worsens with movement.

Learn more about the different types of fistulas, including symptoms, causes, and treatment options.

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Fistulas are very common in people with Crohn’s disease, affecting 1 in 3 individuals.

A fistula is a narrow passage that occurs when inflammation causes sores, or ulcers, to form. These passages can connect one organ to another or to the outside surface of the body.

Various types of fistulas can occur in different places in the body. These include:

  • Anal (perianal): This fistula connects the anal canal or rectum to the surface of the skin close to the anus.
  • Colovesical (bowel to bladder): A rare tract between the colon and bladder, which may allow fecal matter to appear in the urine.
  • Gastrointestinal (bowel to bowel): This fistula connects the intestine to an adjacent organ or surface.
  • Enterocutaneous (bowel to skin): An atypical tract between the intestinal tract or stomach and the skin.

Diagnosing types of fistulas

Diagnosing fistulas varies according to the type. A healthcare professional will have to gather information, such as:

  • where the fistula opens
  • the route of the fistula
  • how many tunnels are present
  • whether the fistula goes through the sphincter muscles
  • whether there is an infection

Read more about how Crohn’s disease affects the body.

An anal fistula is a small tunnel that develops between the end of the bowel and the skin near the anus.

Symptoms of an anal fistula include:

  • skin irritation around the anus
  • a throbbing pain that may worsen with movement, a bowel movement, or coughing
  • smelly discharge near the anus
  • passing pus or blood
  • swelling and redness around the anus
  • difficulty controlling bowel movements

These symptoms are more likely to occur in people with Crohn’s disease.

Other causes may include:


To diagnose this type of fistula, a healthcare professional will conduct a physical examination of the skin surrounding the anus, as fistulas often present as small holes or bumps. They may also press on the skin to determine if there is a leak of puss or feces.

Medical professionals may perform the diagnosis under a general anesthetic so that the area is fully relaxed.

Sometimes, healthcare professionals use a probe to determine where the fistula travels and whether it goes through the sphincter muscles. Several tests can also attempt to determine this, including:

  • a pelvic MRI
  • endoanal ultrasound
  • fistulography, which involves using a dye in the anus to find signs of leakage

Often, healthcare professionals use a combination of these techniques to assess a fistula.

A bladder fistula, or colovesicular fistula, occurs when an opening forms between the bladder and another organ or the skin.

The most common types of bladder fistulas occur between the bladder and the bowel or between the bladder and the vagina.

Symptoms include:

This type of fistula can occur as a result of Crohn’s disease, injury or trauma to the bladder, bowel or gynecologic cancer, or radiation therapy.


To detect this type of fistula, a urologist will perform a physical exam and gather medical history.

They may place a long, thin camera in the urethra to view the bladder — a procedure known as cystoscopy.

They may also use a test called a poppy seed test. This involves individuals eating poppy seeds — if they end up in the urine, it shows there is a fistula from the bowel to the bladder.

X-rays or CT scans can also check the bladder and surrounding areas.

A gastrointestinal (GI) fistula, or bowel to bowel fistula, connects the intestine to an adjacent organ or surface.

Digested food cannot move properly through the body if a person has a GI fistula. The fistula also may cause fluid to leak through.

Symptoms can include:

Around 85% to 90% of GI fistulas occur due to complications with surgery. Other possible causes include:

  • infections or abscesses
  • Crohn’s disease
  • blockage or obstruction in the intestine
  • radiation to the abdomen
  • cancer


A healthcare professional may perform an upper and lower intestinal X-ray. They will administer barium orally or by enema before taking any X-ray images. If there are signs of leaking in the intestines, this will confirm the presence of a fistula.

CT and MRI scans with oral or rectal contrast may also show bowel to bowel fistulas. Some healthcare professionals may also use an endoscopy to help diagnose the issue.

Learn more about gastrointestinal fistulas.

An enterocutaneous fistula, or bowel to skin fistula, is an atypical connection between the intestinal tract or stomach and the skin.

As a result of this connection, contents of the stomach or intestines may leak through to the skin.

Symptoms include:

  • diarrhea
  • dehydration
  • malnutrition

These fistulas usually occur after bowel surgery, but other causes may include:

  • perforated peptic ulcer
  • Crohn’s disease
  • abdominal injury or trauma, such as a stabbing or gunshot


Tests, such as CT scans or a fistulogram, can also help healthcare professionals diagnose this type of fistula.

A barium test, which involves individuals swallowing barium or taking it as an enema before an X-ray, can help confirm the presence of a fistula.

A fistulogram, which involves injecting dye into the fistula area where the skin is open and leaking, can help reveal any blockages.

Treating a fistula depends on the type and whether the individual is receiving treatment for another bowel condition. People can manage most fistulas with medication, surgical procedures, or a combination of the two.


There are different medications that healthcare professionals may prescribe to individuals with fistulas. These include:


Fibrin glue is currently the only nonsurgical treatment for anal fistulas. It involves the surgeon injecting glue into the fistula while a person is under a general anesthetic. The glue helps seal the fistula and encourages it to heal.

This treatment is generally less effective than surgical procedures, and the results may not be long lasting. It may be useful for certain types of fistulas because they do not require cutting.


Doctors can remove anal fistulas via different surgical procedures, including:

  • Fistulotomy: This is an effective strategy for treating most fistulas. However, doctors cannot perform the procedure when the fistula crosses the anal sphincter muscles.
  • Transanal mucosal advancement flap: This method involves removing the fistula and covering the hole with a flap of tissue from inside the rectum. However, this procedure has a lower success rate than a fistulotomy.
  • Ligation of the intersphincteric tract (LIFT): Doctors make a cut in the skin above the fistula and move apart the sphincter muscles. While LIFT has had some promising results so far, more research is necessary to determine its short- and long-term success.
  • Plug: This is a cone-shaped plug consisting of animal tissue that blocks the internal opening of the fistula. It is a suitable alternative for simple fistulas but has a high failure rate of around 44%. Research shows that even though it can be a useful treatment when others have not been effective, it should not be the first treatment of choice.
  • Laser surgery: This treatment involves using a small laser beam to seal the fistula. There are uncertainties around how well it works, but there are no major safety concerns.
  • Seton placement: This is a common treatment for anal fistulas that involves placing a seton, a thin rubber drain, in the fistula, which allows the tunnel to slowly heal. Often, doctors place a series of these over time for gradual healing.

Learn more about fistula surgery.

What to expect from the procedures

Currently, none of the procedures for fistulas have a guaranteed success rate, with 1 in 3 people having a fistula relapse. This means that individuals may need more than one operation to try to treat their fistula.

If a person has a fistula and is considering a surgical option, they can consult a healthcare professional. The following are questions they may wish to ask a healthcare professional about procedures to correct fistulas:

  • What is the success rate of each surgical option?
  • What are the side effects?
  • If there is a fistula relapse, what would be the next step?
  • About how much time passes between a surgical option and a fistula relapse?
  • What can I do to help ensure the procedure is successful?

Atypical tunnels, called fistulas, are a common complication of Crohn’s disease.

Fistulas may go unnoticed or present with symptoms, including pain, discomfort, malabsorption, diarrhea, and more.

There are various treatments to help individuals with fistulas. If a person is experiencing any unusual symptoms, they should speak with a healthcare professional.