Complications from an anal fistula are usually the result of fistula surgery. They can include infection, bowel incontinence or the fistula reoccurring.

Infection

Any type of surgery carries a risk of infection. If the fistula is not completely removed, for example because you are having the surgery carried out in several stages, an infection in the tract (channel) can sometimes spread to other parts of the body.

If this happens, you may require a course of antibiotics (medication to treat infections that are caused by bacteria). If the infection is severe, you may need to be admitted to hospital so that antibiotics can be administered through a drip in your arm (intravenously).

Incontinence

In some cases, surgery can damage the anal sphincter muscles (the ring of muscles that open and close the anus). If the muscles are damaged, you may lose control of your bowels, leading to faeces leaking uncontrollably from your rectum (the area where they are stored). This is known as faecal or bowel incontinence.

The likelihood of incontinence occurring after surgery will depend on the type of surgery you had and the position of your fistula. If you had some bowel incontinence before surgery, this may get worse.

Incontinence after a fistulotomy (surgery that opens up the fistula) is more common in women and in people with Crohn's disease, a condition that causes inflammation of the lining of the digestive system. Rates of incontinence vary, although most studies report incontinence in between 3% and 7% of people.

After using seton techniques, the incontinence rate is 17%, and after an advancement flap procedure the incontinence rate is around 6-8%. Ask your surgeon about the risks associated with your procedure.

Reoccurrence of the anal fistula

In some cases, the fistula can reoccur despite surgery. After having a fistulotomy, the reoccurrence rate is 21%. After an advancement flap procedure, the reoccurrence rate may be as high as 36%.