What is a gastrointestinal fistula?

A gastrointestinal fistula (GIF) is an abnormal opening in your digestive tract that causes gastric fluids to seep through the lining of your stomach or intestines. This can result in infection when these fluids leak into your skin or other organs.

GIF most commonly occurs after intra-abdominal surgery, which is surgery inside your abdomen. People with chronic digestive problems also have a high risk of developing a fistula.

There are four main types of GIFs:

1. Intestinal fistula

In an intestinal fistula, gastric fluid leaks from one part of the intestine to the other where the folds touch. This is also known as a “gut-to-gut” fistula.

2. Extraintestinal fistula

This type of fistula occurs when gastric fluid leaks from your intestine to your other organs, such as your bladder, lungs, or vascular system.

3. External fistula

In an external fistula, gastric fluid leaks through the skin. It’s also known as a “cutaneous fistula.”

4. Complex fistula

A complex fistula is one that occurs in more than one organ.

There are several different causes of GIFs. They include:

Surgery complications

About 85 to 90 percent of GIFs develop after intra-abdominal surgery. You’re more likely to develop a fistula if you have:

  • cancer
  • radiation treatment to your abdomen
  • a bowel obstruction
  • surgical suture problems
  • incision site problems
  • an abscess
  • an infection
  • a hematoma, or blood clot under your skin
  • a tumor
  • malnutrition

Spontaneous GIF formation

A GIF forms without a known cause in about 15 to 25 percent of cases. This is also called a spontaneous formation.

Inflammatory bowel diseases, such as Crohn’s disease, can cause GIFs. As many as 40 percent of people with Crohn’s disease develop a fistula at some point in their lives. Bowel infections, such as diverticulitis, and vascular insufficiency (inadequate blood flow) are other causes.


Physical trauma, such as gunshot or knife wounds that penetrate the abdomen, can cause a GIF to develop. This is rare.

Your symptoms will be different depending on if you have an internal or external fistula.

External fistulas cause discharge through the skin. They’re accompanied by other symptoms, including:

  • abdominal pain
  • painful bowel obstruction
  • fever
  • elevated white blood cell count

People who have internal fistulas may experience:

  • diarrhea
  • rectal bleeding
  • a bloodstream infection or sepsis
  • poor absorption of nutrients and weight loss
  • dehydration
  • worsening of the underlying disease

The most serious complication of GIF is sepsis, a medical emergency in which the body has a severe response to bacteria. This condition may lead to dangerously low blood pressure, organ damage, and death.

Contact your doctor if you experience any of these symptoms after surgery:

  • a significant change in your bowel habits
  • severe diarrhea
  • fluid leakage from an opening in your abdomen or near your anus
  • unusual abdominal pain

Your doctor will first review your medical and surgical history and assess your current symptoms. They might run several blood tests to help diagnose a GIF.

These blood tests will often assess your serum electrolytes and nutritional status, which is a measure of your levels of albumin and pre-albumin. These are both proteins that play an important role in wound healing.

If the fistula is external, the discharge may be sent to a laboratory for analysis. A fistulogram may be done by injecting contrast dye into the opening in your skin and taking X-rays.

Finding internal fistulas can be more difficult. Your doctor may run these tests:

  • An upper and lower endoscopy involves the use of a thin, flexible tube with a camera attached. This is used to view possible problems in your digestive or gastrointestinal tract. The camera is called an endoscope.
  • Upper and lower intestinal radiography with contrast medium may be used. This can include a barium swallow if your doctor thinks you might have a stomach or intestinal fistula. A barium enema may be used if your doctor thinks you have a colon fistula.
  • An ultrasound or CT scan can be used to find intestinal fistula or abscessed areas.
  • A fistulogram involves injecting a contrast dye into the opening of your skin in an external fistula and then taking X-ray images.

For a fistula involving the major ducts of your liver or pancreas, your doctor may order a special imaging test called a magnetic resonance cholangiopancreatography.

Your doctor will do a thorough assessment of your fistula to determine the likelihood of it closing on its own.

Fistulas are classified based on how much gastric fluid is seeping through the opening. Low output fistulas produce less than 200 milliliters (mL) of gastric fluid per day. High output fistulas produce about 500 mL per day.

Some types of fistulas close on their own when:

  • your infection is controlled
  • your body is absorbing enough nutrients
  • your overall health is good
  • only a small amount of gastric fluid is coming through the opening

Your treatment will focus on keeping you well-nourished and preventing wound infection if your doctor thinks your fistula may close on its own.

Treatments may include:

  • replenishing your fluids
  • correcting your blood serum electrolytes
  • normalizing an acid and base imbalance
  • reducing the fluid output from your fistula
  • controlling infection and guarding against sepsis
  • protecting your skin and providing ongoing wound care

GIF treatment can take weeks or even months. Your doctor may recommend surgically closing your fistula if you haven’t improved after three to six months of treatment.

Fistulas close on their own about 25 percent of the time without surgery in people who are otherwise healthy and when smaller amounts of gastric fluid are being produced.

GIFs most often develop after abdominal surgery or as a result of chronic digestive disorders. Talk to your doctor about your risks and how to spot symptoms of a developing fistula.