Anal Fistula and Anal Fissure

Fistula in Ano

The anus is an external opening through which faeces is expelled out of your body. There are a number of small glands inside the anus. These glands may sometimes become blocked and form an infected cavity called an abscess. Often, anal abscesses further develop into an anal fistula. An anal fistula is a small channel or tunnel that develops from the infected gland and opens out onto the skin near the anus.

Some fistulae have only one opening, while others are branched into many openings. The ends of the fistulae look like holes on the surface of the skin around the anus.

Fistulae may sometimes be connected to the sphincter muscles, the muscles that open and close the anus. If this is the case and the fistulae damage the integrity of these muscles, the risk of faecal incontinence is increased.

Anal fistulae are treated through surgery.

Signs and symptoms

The commonly observed symptoms of an anal fistula are often intermittent and may include:

  • Throbbing pain that may get severe when sitting
  • Irritation of the skin around the anus
  • Swelling, tenderness, redness
  • Bleeding
  • Discharge of malodorous pus followed by an alleviation of the pain
  • Pain during bowel movement
  • Fever and fatigue


Anal fistulae result when an anal abscess bursts into the tissues surrounding the anus. This condition is common in young adults, but can occur at any age. The reason why some people develop a fistula, and others don’t is not known. Smoking and Crohn’s Disease have both been shown to increase your risk of developing a fistula.


  • A full medical history will be taken.

Physical examination to find the fistula opening and to track the path of the channel, felt as a hard cord-like structure below the skin.

This may include:

  • A digital rectal examination (insertion of a gloved finger into the anus) may be performed to find the internal opening of the fistula, the presence of any branching and the functioning of the sphincter muscles.
  • A Fistula probe (a tiny instrument inserted into the rectum) may also be used.
  • Anoscope- a small instrument used to view the anal canal.
  • Less commonly a Computerised Tomography (CT) scan or Magnetic Resonance Imaging (MRI) scan may be ordered for complex fistulae with many branches, to evaluate the exact position of the tracts to determine the most appropriate operative approach.


Due to their proximity to the anal sphincter muscles, surgery on anal fistulae is performed with as little impact as possible to reduce the risk of incontinence: Each patient will therefore be assessed individually, based on their examination results. This will often depend on the fistula’s location and complexity, and the strength of the patient’s sphincter muscles.

For SIMPLE fistulae

Simple fistulae are those with a single tract that involves less than 30% -50% of the internal anal sphincter. The preferred treatment of a simple fistula is to lay it open in a procedure called Fistulotomy. This is a small operation under general anaesthetic. The surgeon first probes to find the fistula’s internal opening. Then the tract is cut open, a probe is inserted, the tract is scaped and infected contents flushed out. The overlying skin is then cut to allow the tract to heal as a shallow ulcer.

For COMPLEX Fistulae

Complex fistulae, are those with multiple tracts, those that involve more than 30-50% of the external sphincter, those that involve the anterior half of the anus (in women), any fistula as a result of radiation or Crohn’s disease, and those arising in someone with already compromised sphincter function (i.e. weak anal tone prone to incontinence). These cannot simply be laid open, and often the first step is to control the sepsis by inserting a Seton (see below).

A more complicated fistula, such as a horseshoe fistula (where the tract extends around both sides of the anal canal and has external openings on both sides of the anus), is treated by usually laying open just the segment where the tracts join and the remainder of the tracts are removed.

The surgery may be performed in more than one stage if a large amount of muscle must be cut. The surgery may need to be repeated if the entire tract can’t be found.

Advancement flap procedures: This procedure is usually preferred if the fistula is complex or if the patient is at a high risk of developing incontinence. The fistula tract is removed. A small piece of tissue (advancement flap) is removed from the rectum or from the skin around the anus and attached over the opening of the fistula.

Seton Placement

A Seton (silk string or rubber band is used to control infection relation to the anal muscles.

The Seton may also aid in the drainage of the fistula.

Fibrin Glue or Collagen plug – In some cases, fibrin glue, made from plasma protein, may be used to seal and heal a fistula as opposed to cutting it open. The glue is injected through the external opening after clearing the tract and stitching the internal opening closed. A plug of collagen protein may also be used to seal and close the fistula tract.

Post-operative care

After the surgical procedure, your doctor will discharge you from the hospital on the same day or after a few days based on your condition. It might take 6 weeks for the wound to heal completely. Your doctor may prescribe analgesics to relieve the pain, antibiotics and laxatives. You will be advised to carefully wash, clean and dry your anal area and not to sit or walk for a prolonged period until healing occurs.

Risks and complications

Anal fistula surgery is generally safe with no major risks. However, like most surgeries, anal fistula surgeries may involve complications such as:

  • Infection
  • Narrowing of anal canal
  • Damage of sphincter muscles leading to incontinence
  • Recurrence of fistula
  • Bleeding

As part of the pre-surgical process, you will be advised to stop smoking, fast for about 6 hours before the surgery, and you may be given an enema an hour before the surgery to empty your lower bowel.

Anal Fissure

An anal fissure is a tear in the skin around the opening of the anus (the last part of the digestive tract that controls the removal of stools). An anal fissure is associated with pain and bleeding during bowel movements. The condition is more common after childbirth but it can happen at any age.

Anal fissures are usually caused by trauma or injury to the anal canal while passing hard or large stools, constipation, diarrhoea or childbirth.
Most anal fissures can be diagnosed by a physical examination which involves viewing the anal region and reviewing your medical history. In some cases, diagnosis is done by digital rectal examination or using an instrument called an anoscope. The anoscope is a short instrument with a lighted tube, which can help the doctor view and examine the fissure.
Anal fissures usually heal spontaneously in a few days or weeks (acute), but in cases when it doesn’t heal even after 6 weeks (chronic), medical treatment or surgery is recommended.

Treatment usually involves adopting simple measures to keep your stool soft such as by increasing fibre and fluid intake. Soaking in warm water for 10 – 20 minutes as often as possible, particularly after bowel movements, also helps with healing and reducing discomfort. If symptoms still persist, therapeutic creams may be recommended by your doctor. Topical anaesthetics and pain medication may also be prescribed to control pain.

Surgery is recommended if the symptoms do not respond to conservative treatment. The surgical procedures include:

Lateral internal sphincterotomy

  • Fissurectomy which involves surgically removing the anal fissure leaving an open wound to heal naturally.
  • Advancement anal flaps which involves replacing broken tissue with healthy tissue derived from a different part of the body

Lateral sphincterotomy is the most common surgical procedure indicated for the treatment of anal fissures. The surgery is performed under general anaesthesia as a hospital day case.

The surgery involves making a small cut or incision in the sphincter muscle to reduce the tension in your anal canal, which allows the anal fissure to heal. The incision can be closed or left open to heal.

After the surgery, you will be prescribed painkillers for pain relief. The dressing needs to be removed before having a bowel movement. Complete recovery from anal fissure surgery might take several months, but this varies between individuals.

As with any surgery, the anal fissure surgery involves certain complications such as risk of infection and anal incontinence, the inability to control gas and loss of solid stool.