An anal fistula is an abnormal tunnel under the skin that connects the anal canal in the colon to the skin of the buttocks. Most anal fistulas form in reaction to an anal gland that has developed an abscess, or a pus-filled infection.
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
Drainage of pus near the anal opening
Who's at risk
If you develop an anal abscess, you have about a 50 percent chance of developing an anal fistula. Even if your abscess drains on its own, you have about the same risk for a fistula.
Certain conditions that affect your lower digestive tract or anal area may also increase your risk. These include:
If you have symptoms that suggest an anal fistula, your doctor may refer you to a specialist who deals with colon and rectal diseases. The specialist will ask about your symptoms and your medical history. During your physical exam, the doctor will look for a fistula opening near your anal opening. He or she may press on the area to see if it is tender and if pus comes out. Various techniques may be used to help with the diagnosis, such as:
Guiding a long, thin probe through the outer opening of the fistula and possibly injecting a special dye to find out where it opens up on the inside
Using a scope to look inside your anal canal
Imaging studies, such as ultrasound, which creates an image of the anal area using sound waves, or MRI, which makes images of the area through the use of special magnets and a computer
Once you have an anal fistula, antibiotics alone will not cure it. You will need to have surgery to cure the fistula.
Surgical treatment options include:
Opening up the fistula in a way that allows it to heal from the inside out. This is called a fistulotomy and is usually an outpatient procedure.
Filling the fistula with a special glue or plug, which is a newer type of treatment that closes the inner opening of the fistula. The doctor then fills the fistula tunnel with a material that your body will absorb over time.
In some cases, having reconstructive surgery or surgery that is done in stages.
Complications include a fistula that recurs after treatment and an inability to control bowel movements, called fecal incontinence. This is most likely if some of the muscle around the anal opening, called the anal sphincter, is removed.
When to call the doctor
Call your doctor if you have symptoms of an anal fistula, especially if you have a history of a previous anal abscess. If you have been treated for an abscess or fistula, let your doctor know right away if you have any fever, chills, redness, swelling, bleeding, discharge, constipation, or trouble controlling your bowel movements.
Managing anal fistula
When recovering from anal fistula treatment, make sure to take pain medication as directed by your surgeon. Finish all antibiotics and do not take any over-the-counter medications without first talking to your doctor.
Other important instructions may include:
Soaking in a warm bath three or four times a day
Wearing a pad over your anal area until healing is complete
Resuming normal activities only when you are cleared by your surgeon
Eating a diet high in fiber and drinking plenty of fluids
Using a stool softener or bulk laxative as needed