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What is a Crohn’s Perianal Fistula?

Crohn's disease is a type of inflammatory bowel disease that causes inflammation in the digestive tract, which includes the stomach and intestines. If the inflammation isn't managed well, then it can lead to a perianal fistula—an abnormal connection between the rectum and the skin around the anus. It’s like a tunnel, going from one place to another, that shouldn’t be there. About 20% of people with Crohn's disease will develop a fistula during their lifetime.

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Crohn’s perianal fistulas can be very bothersome and even painful. Symptoms that people may have include oozing of pus, blood or stool from the tunnel opening. They can have pain in the rectum or anus, especially when sitting, passing stool, or doing physical activities. Some people may even have a fever and develop an infected, painful lump or boil near the anus called an abscess.


Most Crohn’s perianal fistulas happen because inflammation inside the rectum or anus spreads to areas outside of the gastrointestinal tract. This causes the fistula, or tunnel, to form. We're still trying to understand why some people with Crohn’s disease develop perianal fistulas while others don’t. It might be due to differences in people’s genetics or the type of bacteria that live in their intestines (i.e., microbiome). Either way, it is very important to treat the inflammation from Crohn’s disease. By stopping the inflammation, it will help stop the fistulas from forming in the first place.

I was in lots of pain [from my fistula], a lot of gas and bloating. I was embarrassed to go out with my friends.

First Step—Talk to Your Doctor! 

It’s common to feel embarrassed or nervous to talk to your doctor about your symptoms... and that’s okay. However, since the fistula generally won’t close on its own, it’s very important to have it checked by a doctor so you can get treated. Fistulas can get better with medications and/or surgical procedures. The first step to healing is to talk to your doctor, who will ask questions to learn more about your symptoms and exam the area.


Successfully treating a fistula usually requires working with a gastroenterology doctor and/or colorectal surgeon. The gastroenterology doctor may recommend medicines to treat your Crohn’s disease and perianal fistulas. The colorectal surgeon, on the other hand, may need to do an outpatient surgical procedure to help close the fistula. If you are looking for a gastroenterology doctor or colorectal surgeon who specializes in diagnosing and treating Crohn’s perianal fistula, click below to find one in your area. 

Diagnosing Crohn’s Perianal Fistula

The first thing your doctor will do is look at the skin around your buttocks and anus. They will check for any small holes or raised red spots that could be a fistula. They may press on the skin to see if any pus, stool, or mucus leaks out.


Sometimes, a colorectal surgeon may need to take a closer look during an outpatient procedure called an “exam under anesthesia.” After giving you sleeping medicine, they closely exam the area and may use a special probe to follow the fistula’s path and see where it begins. During this procedure, the surgeon may also drain any abscesses they see and/or thread a small, soft flexible tube called a seton through the fistula (more on this later).


Imaging Tests

Your doctor may also recommend imaging tests to better look at the fistula. These tests may include:

Pelvis MRI

An MRI machine takes 3D pictures of your pelvis

Endoanal Ultrasound

An ultrasound machine takes images of the area around your anus


Special liquid (i.e., contrast) is injected into the fistula and X-ray pictures are taken afterwards (this is less common nowadays)

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