What Is a Fistula?

An abnormal connection of two body cavities

A fistula is an abnormal connection of two body cavities or a body cavity and the skin. For example, fistulas can occur between the rectum and the vagina or the intestine and the skin. They form when sores caused by inflammation inside the body worsen to the point that they form a tunnel in internal tissues.

There are several causes of fistulas, including abscesses, surgery, and Crohn's disease. Symptoms depend on the location of the fistula. A fistula between the intestine and bladder, for example, may cause cloudy or bloody urine and urinary tract infections.

Fistulas must be treated, but the extent of treatment needed—which can range from medication to surgery—depends on the severity.

Types of Fistulas

Fistulas often occur in the area around the genitals and anus (known as the perineum).

The four types of fistulas are:

  • Enterocutaneous: This type of fistula is from the intestine to the skin. An enterocutaneous fistula may be a complication of surgery. It can be described as a passageway that progresses from the intestine to the surgery site and then to the skin.
  • Enteroenteric or enterocolic: This is a fistula that involves the large or small intestine.
  • Enterovaginal: This is a fistula that goes to the vagina.
  • Enterovesicular: This type of fistula goes to the bladder. These fistulas may result in frequent urinary tract infections or the passage of gas from the urethra during urination.

Where Fistulas Form

Parts of the body that fistulas can form between include:

  • The skin and anus (fistula-in-ano)
  • The neck and throat
  • The bowel and vagina
  • The cervix and vagina
  • The naval and gut

Note that an arteriovenous (AV) fistula, which is a connection between an artery and a vein, is commonly created surgically for patients in need of dialysis. Creating an AV fistula increases blood flow into a vein, providing good access to blood vessels.

What Causes a Fistula?

Fistulas commonly form because of an abscess, a pocket of pus in the body. The abscess may be constantly filling with body fluids such as stool or urine, which prevents healing. Eventually, it breaks through to the skin, another body cavity, or an organ, creating a fistula.

Trauma by way of injury or surgery is another common cause.

Fistulas are also especially common in Crohn's disease. The chronic inflammation associated with the disease can cause sores in the digestive tract that become so significant that they form a channel in the bowel wall. Up to 50% of people with Crohn's disease develop fistulas within 20 years of diagnosis.

Although rare, inflammatory and infectious conditions like diverticulitis and tuberculosis can cause fistulas.

Fistula Symptoms

Fistula common symptoms
Verywell / Nusha Ashjaee

General symptoms of fistulas, which can vary based on the severity of your case, can include:

Additional symptoms can occur depending on the location of the fistula.

For example, a fistula between the vagina and intestine can cause gas or stool to leak through the vagina. A fistula between the intestine and the skin can result in a painful boil or the drainage of fluid or stool through the skin.

How Fistulas Are Diagnosed

Fistulas are usually diagnosed through the use of a physical exam, a computed tomography (CT) scan, and, if needed, other tests such as a barium enema, colonoscopy, sigmoidoscopy, upper endoscopy, or fistulogram.

During a fistulogram, a dye is injected into the fistula, and X-rays are taken. The dye helps the fistula to show up better on the X-rays. The dye is inserted into the rectum, similar to an enema, for fistulas that are in the rectum. The dye must be 'held' inside during the procedure.

With a fistula that opens to the outside of the body, the dye is put into the opening with a small tube. X-rays will be taken from several different angles, so a patient may have to change positions on the X-ray table. As with any other kind of X-ray, remaining still is important.

When it's suspected that a patient has an enterovesicular (bladder) fistula, an intravenous pyelogram (IVP), another type of X-ray, may be performed.

Prepping for this test may include a clear liquid diet or fasting because stool in the colon can obstruct the view of the bladder. The dye (contrast material) is injected into the arm, and several X-rays are taken.

Potential Complications

A fistula may cause complications. In some cases, fistulas might not heal and become chronic. Other potential complications include fecal incontinence, sepsis, perforation, and peritonitis.

Sepsis is a life-threatening illness that results from the body's response to a bacterial infection. Symptoms of sepsis include:

  • Chills
  • Confusion
  • Disorientation
  • Fever
  • Rapid breathing and heart rate
  • Rash

Peritonitis is an inflammation or infection of the peritoneum, the tissue on the abdominal's inner wall that covers the abdominal organs. Symptoms of peritonitis include:

  • Abdominal pain and tenderness
  • Chills
  • Fever
  • Joint pain
  • Nausea
  • Vomiting

Fistula Treatments

Treatments for fistulas vary depending on their location and severity of symptoms. Medical treatments include Flagyl (an antibiotic), 6-MP (an immunosuppressant), or certain biologic therapies (including Remicade and Humira).

An enteral diet may be prescribed for enterovaginal, enterocutaneous, and enterovesicular fistulas. An enteral diet is liquid nutrition that is taken by mouth or given through a feeding tube.

Liquid nutrition formulas replace solid food and contain vital nutrients. With no solid food, there is less stool passing through the anus, which helps the fistula heal and maybe even close.

However, many fistulas will not respond to any of the above therapies and will require surgery and/or wound care. If the fistula is in a healthy part of the intestine, it may be removed without taking out any part of the intestine. If the fistula is in a very diseased part of the bowel, a resection may have to be performed.

A resection may result in a temporary ileostomy. Stool is diverted through the ileostomy, giving the part of the intestine with the fistula time to heal. This type of surgery is most often done on rectovaginal or enterovesicular fistulas. Generally, wounds from fistula surgery can take several weeks to several months to heal.


The location and severity of the fistula play a major role in determining treatment. A fistula is a sign of serious inflammatory bowel disease (IBD), and without proper care, it can lead to serious complications.

Seeing a gastroenterologist on a regular basis and taking medication as prescribed is vital to the management and prevention of IBD complications.

Frequently Asked Questions

  • Is a fistula cancerous?

    Fistulas are generally not cancerous. Anal fistulas that remain inflamed for up to 10 years or more have led to very few instances of cancer (less than 0.2% of anal fistula cases).

  • How long does a fistula take to heal?

    Healing times for a fistula can vary, especially when non-surgical treatments are used. When a fistula requires surgery, the surgical wound generally takes several weeks to several months to heal.

  • Does a fistula bleed?

    Although rare, a fistula can bleed. Bleeding is more common for specific types of fistulas, such as one between the small or large intestine and the skin or a fistula between the aorta (main artery) and the small or large intestine.

18 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Crohn’s & Colitis Foundation. Fistula Removal

  2. Stanford Health Care. Conditions Treated by Fistula Repair

  3. University of California San Francisco. Enterocutaneous Fistula

  4. Scozzari G, Arezzo A, Morino M. Enterovesical fistulas: diagnosis and management. Tech Coloproctol. 2010;14(4):293-300. doi:10.1007/s10151-010-0602-3

  5. MedlinePlus. Fistula.

  6. National Institute of Diabetes and Digestive and Kidney Diseases—UCSF Department of Surgery. Vascular access for hemodialysis.

  7. Schwartz DA, Tagarro I, Carmen Díez M, Sandborn WJ. Prevalence of fistulizing Crohn’s disease in the United States: estimate from a systematic literature review attempt and population-based database analysis. Inflammatory Bowel Diseases. 2019;25(11):1773-1779. doi:10.1093/ibd/izz056

  8. Mount Sinai. Fistula.

  9. NIH National Institute of Diabetes and Digestive and Kidney Diseases. Colonic & Anorectal Fistulas.

  10. Medline Plus. Intravenous Pyelogram (IVP)

  11. Johns Hopkins Medicine. Anal Fistula

  12. MedlinePlus. Sepsis

  13. National Kidney Foundation. Peritonitis

  14. Gold SL, Cohen-Mekelburg S, Schneider Y, Steinlauf A. Perianal fistulas in patients with Crohn’s disease, part 1: current medical management. Gastroenterology & Hepatology. 2018;14(8):470-481.

  15. Yan D, Ren J, Wang G, Liu S, Li J. Predictors of response to enteral nutrition in abdominal enterocutaneous fistula patients with Crohn's disease. Eur J Clin Nutr. 2014;68(8):959-963. doi:10.1038/ejcn.2014.31

  16. Crohn’s & Colitis Foundation. Small and Large Bowel Resection

  17. Osone K, Ogawa H, Katayama C, et al. Outcomes of surgical treatment in patients with anorectal fistula cancerSurg Case Rep. 2021;7(1):32. doi:10.1186/s40792-021-01118-6

  18. Wu L, Ren J, Liu Q, et al. Risk factor and outcome for intra-abdominal bleeding in patients with enterocutaneous fistula. Medicine (Baltimore). 2016;95(47):e5369. doi:10.1097/MD.0000000000005369

Additional Reading

By Amber J. Tresca
Amber J. Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16.