Anal fistula

An anal fistula is an abnormal tunnel between the inside of the anus and the skin around the anus. It usually forms after an anal abscess has drained or burst. The fistula remains open and can continue to discharge pus or faecal material.

Anal fistulae do not heal on their own and require medical treatment. Some people develop an anal fistula due to conditions such as Crohn’s disease.

​

Symptoms of an anal fistula

 

Common symptoms include:

• A small opening near the anus, which may be visible or felt

• Persistent discharge of pus, sometimes mixed with blood

• Pain and discomfort around the anal area

• Skin irritation due to ongoing drainage

 

If you notice these symptoms, it is important to seek medical advice to prevent complications.

 

How is an anal fistula diagnosed?

Your consultant will:

• Take a detailed medical history

• Perform a clinical examination, which may include:

  • Rigid sigmoidoscopy – a short camera examination of the rectum

  • Proctoscopy – a closer examination of the anal canal

 

Additional tests may be needed if:

• The fistula cannot be easily located

• The condition is longstanding or recurrent

• You are aged over 40 years and have bleeding or changes in bowel habit, in which case an endoscopic examination (flexible sigmoidoscopy or colonoscopy) may be advised to check bowel health

 

If the area is too painful to examine, your consultant may recommend an examination under anaesthetic (EUA).

 

Treatment for an anal fistula

Surgical options

 

Since anal fistulae rarely heal on their own, treatment usually requires surgery under general anaesthetic. The goal is to remove or close the fistula while protecting the anal sphincter muscle, which controls bowel movements.

 

Types of fistula surgery

• Seton drainage

  • A small drainage tube (seton) is placed through the fistula to allow infection to clear

  • Often used before definitive surgery

​

• Fistulotomy (Laying open the fistula)

  • The fistula is cut open and left to heal naturally

  • Best for simple fistulae that do not pass through the sphincter muscle

 

• Fistula plug or paste

  • A collagen plug or paste is inserted to close the fistula

  • Minimally invasive, but higher risk of recurrence

 

• Cutting seton technique

  • A tight seton is placed through the fistula and gradually tightened

  • Slowly cuts through the sphincter muscle while allowing controlled healing

 

• LIFT procedure (Ligation of Intersphincteric Fistula Tract)

  • Involves tying off both ends of the fistula to close it

  • Suitable for complex fistulae involving the sphincter muscle

 

Some patients may need more than one procedure to fully heal. For guidance on post-surgical care, please refer to our aftercare guide for anal surgery for detailed recovery instructions and tips.