By Kristen Sturt
Toilet with thumbtacks representing fistula, hemorrhoids in IBD patients

Medically reviewed by Jenny Blair, MD 

A common complication of Crohn’s disease (CD) affecting about one of every three patients, a fistula is an abnormal tunnel linking two organs, or linking one organ to the outside of the body. In CD, fistulas typically join different parts of the intestine, or the intestine and the bladder, vagina or skin.

“The simple way to think about it is a connection between two parts of your body that shouldn’t exist,” says Byron Vaughn, MD, a gastroenterologist and assistant professor of medicine at the University of Minnesota Medical School in Minneapolis. They’re caused by inflammation burrowing through your gut wall, he explains, which causes the openings to form.

Fistulas may cause pain and leakage, and often become infected. They can be frustrating and embarrassing, too, damaging self-esteem and impeding overall quality of life. Here’s what you should know about them.

The Basics of Fistulas

Doctors cannot predict for certain who will develop a fistula, but increased CD severity and duration are risk factors. A young age at diagnosis and disease involvement of the rectum or colon are also associated with increased odds. Occasionally, fistulas arise before an official CD diagnosis, meaning some people aren’t aware they have the condition until after one develops.

Fistulas can either be internal, meaning they remain entirely within the body, or external, meaning they break through the skin. They’re most often found in the perianal area. “These are fistulas around the anal canal,” says Manreet Kaur, MD, a gastroenterologist who is medical director of the Inflammatory Bowel Disease Center at Baylor College of Medicine in Houston, Texas. “So, this could be a fistula arising from the rectum out onto the skin.”

Perianal fistulas are always external, and can be simple or complex. Simple ones generally develop below the sphincter muscles and have one tract. They don’t involve complications like abscesses, which Dr. Kaur calls infected “little pockets of pus.”

Complex perianal fistulas are located higher, often involving the sphincter muscles. They often have multiple tracts, says Dr. Vaughn, “and tend to move in horseshoe configurations around the anus and rectum.” They may link to adjacent organs and cause complications, too.

Enterocutaneous fistulas, which link the intestine and skin, are other common external fistulas. Common internal fistulas include:

  • Enteroenteric fistulas, connecting different parts of the intestine
  • Enterovesical fistulas, connecting the intestine and bladder
  • Enterovaginal fistulas, connecting the intestine and vagina, and rectovaginal fistulas, connecting the rectum and vagina
Doctor helping patient, fistulas complication of Crohn's

Fistula Symptoms and Complications

Fistula symptoms are largely determined by its location and severity. Perianal fistulas frequently start with an abscess, presenting with a painful bump or swelling around your anus, along with a fever. “Often, that ends up bursting and creating the fistula,” says Vaughn. After that, he explains, you’ll likely see pus, blood or feces in your underwear.

Enterovaginal fistulas often involve pain, too, along with air, pus or feces in the vagina. With enterovesical fistulas, you may see the same substances in your pee. Plus, says Kaur, “Patients can feel little bubbles of air in their urine, or they may have frequent urinary tract infections.” People with larger enteroenteric fistulas can experience diarrhea and weight loss; smaller ones may be symptomless and heal without treatment.

Though rarely life-threatening, fistulas can trigger additional, serious complications. Chronic active or untreated perianal fistulas may lead to fecal incontinence, for example. And occasionally, fistula-related abscesses can cause sepsis, a severe reaction to bacteria in the body that is sometimes called blood poisoning.

How to Treat and Prevent Fistulas

Fistula treatment is case-by-case and depends on the anatomy of the fistula. Mapping this out for an internal fistula requires imaging, like an MRI or CT scan. For a perianal fistula, you’ll have a physical exam, likely under anesthesia; imaging is often incorporated, as well.

Since it regularly entails both medicine and surgery, fistula management is often a team effort, involving a gastroenterologist and colorectal surgeon. Medications are typically tried first. Antibiotics may be used for healing, lessening discharge and controlling infection. Immunomodulators or anti-TNF drugs are frequently successful for healing and reducing overall inflammation.

While fistulas sometimes heal with medications alone, many require surgery. Perianal fistulas may require surgical abscess drainage, for example. Seton placement, which entails a thread being looped through the fistula to drain bacteria and help prevent further infection, is another common procedure. You can also do a fistulotomy, says Vaughn, “where you basically cut open the fistula and just let it all air out.”

Surgically managing internal fistulas often involves a bowel resection, says Vaughn. During this procedure, a surgeon removes the affected part of the intestine. Flap surgery, in which normal tissue is used to cover a fistula opening, is sometimes helpful, as well.

Complete healing of a fistula can be tough, and they recur in about one-third of patients. Prompt diagnosis and early treatment can keep them from progressing and are crucial to quality of life, so CD patients should reach out to a provider with symptoms. And while there’s no surefire way to prevent fistulas, achieving and maintaining remission goes a long way. “Generally,” says Vaughn, “if you get your Crohn’s under control first, you’ll prevent going on to develop a complication like a fistula.”

Jenny Blair is a writer and journalist covering science, medicine, and the humanities. She earned her MD at Yale University, then completed a residency in emergency medicine at the University of Chicago. After several years in practice, she transitioned to working with words and ideas full-time. Jenny has contributed to Discover, New Scientist, Washington Spectator, and Medtech Insight, among other publications. She lives in New York City.

Oshi is a tracking tool and content resource. It does not render medical advice or services, and it is not intended to diagnose, treat, cure, or prevent any disease. You should always review this information with your healthcare professionals.