Anal fistula


An anal fistula describes a small channel which forms between the end of your bowel (the anal canal) and the skin near your anus. The anus is the outward opening through which faeces are eliminated from your body. 

The end of the fistula may appear to look like a hole in the skin around your anus. It can cause bleeding and discharge while passing stools, which can cause pain and discomfort.  Anal fistulas can be classified as:

  • Simple or complex – this is based on whether you have one fistula tract, or a number of interlinking connections, or

  • Low or high – this depends on the position of the fistula and how near it is to your sphincter muscle (the rings of muscle which open and close the anus).

​An anal fistula is most often due to an anal abscess, which is a painful collection of pus which usually develops following the infection of a gland inside the anus. After an anal abscess bursts, and if the infected fluid has not been entirely drained, it often causes an anal fistula. 

The only real cure for anal fistula is surgical intervention. The GI and Surgery Service Line  at The Aga Khan University Hospital are equipped to assist you with any symptoms that you may be experiencing, whether it be related to an anal fistula or any other problem.

Potential symptoms of an anal fistula include:

  • Irritated skin – the skin around your anus may be irritated, swollen, red and tender.
  • Discharge – you may experience discharges of either pus or blood, especially while passing stools.
  • Recurrent anal abscesses 
  • Fever, chills or generally feeling fatigued 

​You should visit your doctor if you notice any symptoms of an anal fistula, or that worry you.

​Your time with your doctor maybe limited, so make sure to prepare for your visit beforehand. Here​ are some tips to help get you started.

​When you visit your doctor, they will ask about your symptoms and take a look at your medical history. They will then perform a physical and rectal examination. This is nothing to be embarrassed about, and is quite essential for a proper diagnosis. In some cases you may require a proctoscopy to further examine inside your rectum. These are usually sufficient for the doctor to make a diagnosis of an anal fistula. 

However in some cases your doctor may need you to undergo further diagnostic tests, such as an ultrasound, Magnetic Resonance Imaging (MRI) test or Computerized Tomography (CT) scan. This is in order to rule out any other possible underlying causes (e.g. Crohn’s disease or tuberculosis) or necessary if there are several channels (fistula tracts) in order to define their position.  

Most cases of anal fistulas need to be operated on, because they rarely ever heal on their own if not treated. 

There are several different surgical options, and the form of surgery that your surgeon will recommend for you will be dependent on the position of your anal fistula, and whether it is classified as simple or complex. The possible surgical options include:

  • Fistulotomy – This is the most common surgical treatment for anal fistulas and involves making an incision along the entire length of the fistula in order for your surgeon to be able to flush out its contents. 

  • Seton techniques – A seton refers to either a piece of silk thread or rubber band which is used to either aid the removal or part of the sphincter or aid in the drainage of the fistula. 

  • Advanced flap procedures – this is where the fistula is removed and covered with a flap of tissue which is removed from either the rectum or from the skin around your anus. 

Different types of surgery have different indications. Your doctor can help you choosing better treatment option for you depending on your condition.

​Please click here​ for some guidelines on “what to do before your surgery”

Please click here ​for some guidelines on “what to do on the day of your surgery”

​The possible complications of a surgical treatment to treat anal fistulas include:

  • Heavy bleeding

  • An increase in pain, swelling or discharge or pus or blood

  • A high fever

  • Nausea

  • Trouble with passing urine 

  • Worrisome scarring 

  • Constipation 

  • Infection 

  • Bowel incontinence (this refers to the temporary or permanent loss of bowel control)

  • Recurrence 

​Please click here​ for some guidelines on “what to do on after your surgery”

The Aga Khan University Hospital offers various support services to help with managing or recovering from the disease or condition. These include but are not limited to nutrition, physiotherapy, rehabilitation, specialized clinics and some patient support groups. Your doctor or nurse will advise you accordingly.

The Aga Khan University Hospital offers financial assistance to those who are in need and fulfil the eligibility criteria. For further information, you can contact the Patient Welfare Department. You can find the contact number of the Patient Welfare Department in the ‘Important Numbers’ section on the website homepage.

The financial counselling staff is available during office hours, at the main PBSD (Patient Business Services Department), to answer your financial queries on treatments’ costs and authorize admissions on partial deposit as per hospital policies allow. The financial counsellor in the emergency room is open 24/7. You can find the contact number of the Patient Business Services in the ‘Important Numbers’ section on the website homepage.

Your doctor and or nurse will give you specific instructions about the prescribed medication. Please ensure that you take or use the prescribed medicine as advised. It can be dangerous to your health if you self-prescribe. Please inform the doctor or nurse beforehand if you have experienced any adverse reactions to any medications in the past. If you experience any symptoms of drug poisoning, overdose or severe reaction please contact the Pharmacy Service at The Aga Khan University Hospital immediately. You can find the contact number of the Pharmacy Services in the ‘Important Numbers’ section on the website homepage.



The information provided on our website is for educational purposes and not intended to be a substitute for medical advice, diagnosis or treatment. You should always seek the advice of your doctor or other healthcare professional provider. ​