Anal fistula

Also commonly called fistula-in-ano

Anal fistulas are small tunnels that develop between the end of the bowel and the skin near the anus

What is an anal fistula?

An anal fistula is a small, hollow tunnel that develops between the end of your rectum and the skin near your anus. They are normally caused by an infection or inflammatory condition.

Anal fistulas can be unpleasant, leading to discomfort and discharge. Quite often, surgery is the only way to get rid of anal fistulas.

Need to know

  • What are the symptoms of an anal fistula? icon plus

    Symptoms of anal fistulas can range in severity, from mildly bothersome to distressing. They might include:

    • irritated skin around your anus
    • swelling and redness around your anus
    • fever if you also have an abscess
    • constant, throbbing pain
    • unable to control bowel movements
    • smelly discharge from near your anus
    • pus or blood in your stools
  • How is an anal fistula diagnosed? icon plus

    Your GP will discuss your symptoms with you. They may also carry out a physical examination of your back passage. Depending on your symptoms, they may also recommend other tests for a later date.

    These might include:

    • an MRI scan: MRI scans also produce high-quality images but they tend to be used for recurrent fistulas or complex fistulas brought on by Crohn's disease. 
    • an endoanal ultrasound: An endoanal ultrasound is a quick scan that can produce high-quality images of your insides. It tends to be used if anal fistulas are of some clinical concern. 


  • Potential treatment options icon plus

    Quite often, the only way to get rid of anal fistulas is surgery. Your consultant may recommend inserting a seton (a loop of thread that allows drainage and healing of the fistula) or a fistulotomy, which involves cutting the anal fistula so that it heals into a flat scar.

    There are other surgical options, including covering the end of a fistula tunnel with a flap of tissue, small clip or filling it with a special glue. Your consultant will recommend the best course of action for you.

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This content is intended for general information only and does not replace the need for personal advice from a qualified health professional.
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