Anal Fistula

An anal fistula is an abnormal tunnel that develops between the bowel and skin near the outside of the anus, where feces comes out. The anus has a number of tiny glands that make lubricating fluid. Sometimes these glands can become plugged and infected. This may lead to the development of a fluid-filled pocket (abscess). An anal fistula often develops after this infection or abscess. It is nearly always caused by a past or current anal abscess.


Though an anal fistula is almost always caused by a past or current anal abscess, other causes can include:

  • A complication of surgery.

  • Trauma to the rectal area.

  • Radiation to the area.

  • Other medical conditions or diseases, such as:  

  • Chronic inflammatory bowel disease, such as Crohn disease or ulcerative colitis.  

  • Colon or rectal cancer.  

  • Diverticular disease, such as diverticulitis.  

  • A sexually transmitted disease, such as gonorrhea, chlamydia, or syphilis.

  • An HIV infection or AIDS.  


  • Throbbing or constant pain that may be worse when sitting.  

  • Swelling or irritation around the anus.  

  • Drainage of pus or blood from an opening near the anus.  

  • Pain with bowel movements.

  • Fever or chills.


Your caregiver will examine the area to find the openings of the anal fistula and the fistula tract. The external opening of the anal fistula may be seen during a physical examination. Other examinations that may be performed include:

  • Examination of the rectal area with a gloved hand (digital rectal exam).  

  • Examination with a probe or scope to help locate the internal opening of the fistula.  

  • Injection of a dye into the fistula opening. X-rays can be taken to find the exact location and path of the fistula.  

  • An MRI or ultrasound of the anal area.  

Other tests may be performed to find the cause of the anal fistula.  


The most common treatment for an anal fistula is surgery. There are different surgery options depending on where your fistula is located and how complex the fistula is. Surgical options include:

  • A fistulotomy. This surgery involves opening up the whole fistula and draining the contents inside to promote healing.

  • Seton placement. A silk string (seton) is placed into the fistula during a fistulotomy to drain any infection to promote healing.

  • Advancement flap procedure. Tissue is removed from your rectum or the skin around the anus and is attached to the opening of the fistula.

  • Bioprosthetic plug. A cone-shaped plug is made from your tissue and is used to block the opening of the fistula.

Some anal fistulas do not require surgery. A fibrin glue is a non-surgical option that involves injecting the glue to seal the fistula. You also may be prescribed an antibiotic medicine to treat an infection.


  • Take your antibiotics as directed. Finish them even if you start to feel better.

  • Only take over-the-counter or prescription medicines as directed by your caregiver. Use a stool softener or laxative, if recommended.  

  • Eat a high-fiber diet to help avoid constipation or as directed by your caregiver.

  • Drink enough water to keep your urine clear or pale yellow.  

  • A warm sitz bath may be soothing and help with healing. You may take warm sitz baths for 15–20 minutes, 3–4 times a day to ease pain and discomfort.  

  • Follow excellent hygiene to keep the anal area as clean and dry as possible. Use wet toilet paper or moist towelettes after each bowel movement.  


You have increased pain not controlled with medicines.


  • You have severe, intolerable pain.

  • You have new swelling, redness, or discharge around the anal area.

  • You have tenderness or warmth around the anal area.

  • You have chills or diarrhea.

  • You have severe problems urinating or having a bowel movement.  

  • You have a fever or persistent symptoms for more than 2–3 days.  

  • You have a fever and your symptoms suddenly get worse.  


  • Understand these instructions.

  • Will watch your condition.

  • Will get help right away if you are not doing well or get worse.