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Anal Fistula

An anal fistula is a small channel between the anal canal and skin around the anus that happens as the result of an infection.

What is an anal fistula?

If you have an infection in your anal canal, this can cause pus to form. When the pus then leaves the body, it can also leave behind a fistula (a small tunnel).

An anal fistula can also form due to a persistent infection or inflammation of the bowel.

What are the symptoms of an anal fistula?

Symptoms of an anal fistula include:

  • Irritation around your anus
  • Anal swelling / redness
  • Bad-smelling anal discharge
  • Bleeding or pus when you pass a stool
  • Discomfort / throbbing pain around your anus
  • Diarrhoea
  • Fever
  • Bowel incontinence – difficulty controlling your bowel movements (less common)

What causes an anal fistula?

As mentioned, in most cases anal fistulas develop because of an infection, which becomes an abscess. Other, less common potential causes and risk factors include:

  • Having certain other conditions – either to do with bowel infection/inflammation, such as diverticulitis, Crohn’s, or other conditions such anal cancer, rectal cancer, skin condition hidradenitis suppurativa, HIV or tuberculosis
  • Following surgery / radiotherapy around the anus

How is an anal fistula diagnosed?

If you do feel discomfort from what you think is an anal fistula, see your doctor. To make a diagnosis, your doctor will ask you about your symptoms and give you a gentle rectal exam.

You might be referred for other tests, such as a proctoscopy or imaging tests (a CT scan ultrasound or MRI), if your doctor thinks you may have an anal fistula.

How is an anal fistula treated?

Anal fistulas don’t go away on their own without treatment. The first step is to treat the underlying cause, and therefore you may be sent for some diagnostic tests.

If there is evidence of an abscess, you may require antibiotics or surgery to drain the pus. Typically fistulas require surgery to repair them, and it is not uncommon to require multiple treatments.

Surgical options your doctor is most likely to suggest are:

  • Fistulotomy – where the fistula is cut open so it can heal (this will leave a flat scar)
  • The seton procedure – a surgical thread is left in the fistula, usually for several months. This allow the pus to drain out and the infection to settle down. A follow-up procedure will often be required to definitiely treate the fistula
  • A ligation of internal fistula tract (LIFT) procedure – where the fistula tract is divided between the muscles of the bottom
  • Video assisted anal fistula treatment – surgeon to see inside the anal fistula tract and locate the internal opening using an endoscope light. Sometimes the fistula can be cured with multiple treatments

Other options include the fibrin glue, a fistula plug, ligation or an endorectal advancement flap.

Your doctor will advise you on the surgery that’s right for you.

If you’re unsure what treatment you should go for, or the above treatments don’t work for you, our team of expert specialists are here to help.

This content has been checked and approved by

Mr James Kinross  ›

Mr James Kinross is a consultant colorectal surgeon at King Edward VII’s Hospital.

Find your specialist in anal fistula at King Edward VII's Hospital

If you suspect you have an anal fistula and you’re seeking an expert opinion, you can find the UK’s leading anal fistula specialists here at King Edward VII’s Hospital. Our consultants are hand-picked for you, making it easy to access the best possible care.

Mr Eric Alexandre Chung  ›
Special interests include:
Colorectal cancer (+ 12) more
Mr Alexander Von Roon  ›
Special interests include:
Colorectal cancer (+ 30) more
Mr James Kinross  ›
Special interests include:
Colorectal cancer (+ 8) more

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