What is an anal fistula and how is it treated?

A fistula is a narrow tunnel that connects an organ to somewhere else in the body. Developing fistulas is common amongst adults with Crohn’s disease. In fact, about 35-50% of adults with Crohn’s disease will develop a fistula at some point in their disease journey.

There are quite a few different types of fistulas associated with Crohn’s disease. We take a look at the key characteristics of anal fistulas and how they are treated. 

What is an anal fistula?

Fistulas associated with Crohn’s disease come in a few different forms, but the most common type is the anal or perianal fistula. “Peri” means “around,” and translates to a fistula around the anus. An anal or perianal fistula is when the anal canal or rectum connects to the surface of the skin near the anus. These fistulas often follow an infection or abscess that didn’t heal properly.

A few notable signs and symptoms that you may have an anal fistula include: 

  • a tender swelling or lump in the area around the anus
  • frequent anal abscesses
  • pain and irritation that gets worse when you sit down, move around, defecate, or cough
  • bloody stool or foul-smelling pus from an opening around the anus
  • painful bowel movements

If you have any of the symptoms above, it’s important to reach out to your healthcare provider. They may refer you to a physician who specializes in colon and rectal diseases. During your physical exam, the doctor will look for a fistula opening near your anal opening. They may press on the area to see if pus comes out and will try to determine how deep the tract is and the direction in which it is going.

Your doctor may also perform additional tests to confirm an anal fistula diagnosis, such as:

  • Fistula probe: A long, thin probe that is guided through the outer opening of the fistula.
  • Anoscope: A special scope used to look inside your anus and rectum.
  • MRI or Ultrasound: An MRI makes images of the area by using special magnets and a computer. An ultrasound creates an image of the anal area using sound waves.

Other Crohn’s related fistulas include bowel to bladder; bowel to vagina; bowel to skin; and bowel to bowel. 

Treatments for an anal fistula

A combination of medication and surgery is usually needed to treat anal fistulas. 

Medication doesn’t typically fully heal fistulas, but your doctor may prescribe the following: 

  • Antibiotics may help reduce discharge and make your fistula feel more comfortable. It can take around six to eight weeks for a course of antibiotics to work. In some instances, treatment is continued for some months. But antibiotics rarely lead to complete and lasting healing. 
  • Biologics have been shown to bring about and maintain healing in perianal fistulas. These are usually started when any abscesses have been treated with antibiotics.

Up to 1 in 3 people with Crohn’s who have an anal fistula will need an operation at some time. Surgery is almost always necessary to fully cure an anal fistula. The goal is to get rid of the fistula while protecting the anal sphincter muscles, which control the release of bowel movements. The following surgery options are most common for patients with an anal fistula

  • Fistulotomy: This is the most common (and most effective) for many anal fistula patients. In this procedure, the length of the fistula is cut open. This procedure opens up the fistula in a way that allows it to heal from the inside out. It is usually an outpatient procedure. The healing process may take from a week to several months. 
  • Advancement flap: This procedure is used for more complex fistulas where the sphincter muscles are involved and where cutting the fistula tract open would carry a high risk of incontinence. After the fistula tract has been cleaned (while leaving sphincter muscles intact), the fistula is covered with a flap, or piece of tissue, taken from the rectum. 
  • LIFT (Ligation of intersphincteric fistula tract). This operation tries to avoid cutting the sphincter muscle. The surgeon will make a small cut at the entrance to the anal canal. Once the surgeon has found the fistula tunnel crossing the internal and external anal sphincter muscles, it is cut in two. Both ends are then stitched closed.

Most patients respond well to surgery. After the surgery, your doctor may recommend that you soak the affected area in a warm bath, drink plenty of fluids, wear a pad over your anal area, and take stool softeners or laxatives as needed. There are other, experimental treatment options to treat complex anal fistulas. Consult with your physician about the best plan of action for your specific case. 

Researchers are looking for adults with Crohn’s disease to participate in clinical studies. Crohn’s patients with a history of anal fistulas can help advance research. Your participation may even lead to new treatments down the road. Start your search for a clinical trial below.