What is an anal fistula?

The anal canal is the end part of the intestinal tract. It includes the rectum and anus. Sometimes an abnormal passage forms from the anal canal to the skin near the anus. This is called an anal fistula. Anal fistulas can also form from the anal canal to other organs, such as the vagina or urinary tract.

What causes an anal fistula?

An anal fistula most often happens from an anal gland that has developed a pus-filled infection (abscess). A fistula can also happen with certain conditions, such as Crohn’s disease. Or it may happen after radiation therapy for cancer. Injury to the anal canal and surgery can also cause anal fistulas.

Who is at risk for an anal fistula?

Having an anal abscess raises your risk of having an anal fistula. Certain conditions of the lower digestive tract or anal area may also raise your risk. These include:

• Colitis

• Crohn's disease

• Chronic diarrhea

• Radiation treatment for rectal cancer

What are the symptoms of an anal fistula?

The symptoms of an anal abscess and an anal fistula can be similar and may include:

• Pain and swelling around the anal area

• Fever and chills

• Feeling tired and sick

• Redness, soreness, or itching of the skin around the anal opening

• Pus drainage near the anal opening

How is an anal fistula diagnosed?

If you have symptoms that seem like an anal fistula, your healthcare provider may refer you to a specialist for colon and rectal diseases. The specialist will ask about your symptoms and your health history. During your physical exam, the provider will look for a fistula opening near your anal opening. They may press on the area to see if it's sore and if pus comes out. Sometimes, you'll need to have a special exam under anesthesia so the provider can get more information without causing you pain. Different methods may be used to help with the diagnosis. These include: 

• Fistula probe. A long, thin probe is guided through the outer opening of the fistula. A special dye may be injected to find out where the fistula opens up.

• Anoscope. This is a special scope used to look inside your anal canal.

• Imaging tests. These may include an ultrasound, which creates an image of the anal area using sound waves. Or they may include an MRI, which makes images of the area by using special magnets and a computer.

How is an anal fistula treated?

Once you have an anal fistula, antibiotics alone won't get rid of it. You'll need to have surgery to treat the fistula. Surgical treatment includes:

• Fistulotomy. This procedure opens up the fistula in a way that lets it heal from the inside out. It's usually an outpatient procedure. This means you go home the same day.

• Filling the fistula with a special glue or plug. This is a newer type of treatment that closes the inner opening of the fistula. The provider then fills the fistula tunnel with a material that your body will absorb over time.

• Reconstructive surgery or surgery that is done in stages. This may be a choice in some cases.

• Seton placement. This procedure places a stitch (suture) or rubber band (seton) in the fistula that is slowly tightened. It lets the fistula drain and heal behind the seton. It lowers the risk for incontinence.

Anal fistulas are very common in people with Crohn’s disease. For those with both Crohn's disease and a fistula, medical therapy is often tried before surgery.

What are the possible complications of an anal fistula?

Complications of an anal fistula include that it may return after treatment. Another complication is an inability to control bowel movements (fecal incontinence). This is most likely if some of the muscle around the anal opening, called the anal sphincter, is removed.

How do I manage an anal fistula?

When recovering from anal fistula treatment, make sure to take pain medicine as directed by your surgeon. Finish all your antibiotics, even if you're feeling better. Don’t take any over-the-counter medicines without first talking with your provider.

Other important instructions may include:

• Soaking in a warm bath 3 or 4 times a day

• Wearing a pad over your anal area until healing is complete

• Going back to normal activities only when your surgeon says you can

• Eating a high-fiber diet and drinking plenty of fluids

• Using a stool softener or bulk laxative as needed

When should I call my healthcare provider?

Call your healthcare provider if you have symptoms of an anal fistula, especially if you've had an anal abscess in the past. If you've been treated for an abscess or fistula, call your provider or get medical care right away if any of these occur:

• Fever of 100.4°F (38°C) or higher or as directed by your healthcare provider

• Symptoms of the anal fistula return, such as pain or drainage

• Increased pain, redness, swelling, or drainage in or near the anus or rectum

• Trouble controlling your bowel movements

• Hard or painful stools or trouble controlling your bowel movements

• Mucus, pus, or blood (dark or bright red) in the stool

• Belly pain that doesn't respond to treatment or that doesn't go away after a few hours

• Belly swelling that doesn't go away after a few hours

• Vomiting that won’t stop

If the problem returns, see a colon and rectal surgeon. This is a doctor who has completed advanced training in the surgical and nonsurgical treatment of problems of the colon, rectum, and anus.

Key points about an anal fistula

• An anal fistula is an abnormal passage that forms from the anal canal to the skin near the anus.

• Symptoms include pain, swelling, or pus draining from the anal opening.

• This condition often occurs from an anal gland that has developed a pus-filled infection (abscess).

• It can also occur with certain conditions, such as Crohn’s disease. Injury to the anal canal and surgery can also cause it.

• Antibiotics alone won't fix it. You will need to have surgery to cure the fistula.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you don't take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your healthcare provider if you have questions.