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Anal Fistula: Causes, Symptoms, Treatment, And Prevention

Anal fistula (a.k.a Fistula-in-Ano) is a result of an anal abscess. An anal abscess is a painful pus-filled cavity caused due to a bacterial infection around the anus. Most of the anal abscesses are formed due to an infection in the internal glands of the anus. About 30-50% of patients with an anal abscess develop anal fistula, and 80% of all the anal fistulas are formed due to anal infection.

Anal Fistula

What is an Anal Fistula?

An anal fistula is an abnormal opening between the anal canal and external skin of the buttocks. An anal fistula is formed if an anal abscess bursts before it is treated or if the abscess is not healed completely.

Based on the location, anal fistula is classified into following types, they are:

  • An Intersphincteric Fistula is an abnormal tract that begins between the internal and external sphincter muscles and ends in the anus region.
  • Transphincteric Fistula (a.k.a Horseshoe Fistula) is an abnormal, inflamed tract that crosses the external sphincter and opens outside the anal region.
  • A Suprasphincteric Fistula is an abnormal tract that begins between the internal and external muscle space and crosses the puborectal muscle and opens outside the anus.
  • An Extrasphincteric Fistula is an abnormal tract that begins at the rectum and crosses the muscle and opens around the anus. It is usually caused by appendiceal abscess, Crohn’s disease.

What are the Causes of an Anal Fistula?

An anal fistula is mostly caused due to the development of an anal abscess that does not heal properly even after the drainage of pus.

Other causes of anal fistula include:

  • Crohn’s Disease is a condition which causes inflammation of the intestine
  • Diverticulitis is an infection or inflammation of the tiny pouches that sticks to the sides of the colon.
  • Hidradenitis Suppurativa is an inflammatory skin condition that causes abscesses and scarring

Symptoms of an Anal Fistula:

The most common symptoms of an anal fistula include:

  • Irritation of the skin around the anus
  • Pain around the anal region that gets worse while sitting, walking, coughing
  • Redness of the skin around the anus
  • Fever associated with chills
  • Fatigue
  • Painful bowel movement
  • Foul smell from the anus
  • Rectal bleeding

Risk Factors of Anal Fistula:

 The risk of developing an anal fistula increases if an individual develops an anal abscess. Certain conditions that increase the risk of developing an anal fistula include:

  • Radiation therapy for rectal cancer
  • Diabetes
  • Dermatosis
  • Excessive intake of spicy food
  • Smoking
  • Hyperlipidemia
  • Tuberculosis
  • Sedentary lifestyle
  • Consumption of alcohol
  • Sexually transmitted diseases like chlamydia and syphilis

Diagnosis of an Anal Fistula:

The doctor initiates the diagnosis by reviewing the medical history and signs and symptoms of the individual.

Physical Examination:

A physical examination is performed to detect the fistula opening, tenderness and drainage of pus near the anal region. The doctor gently presses around the fistula to determine the tenderness and bloody discharge.

Locating an external opening of an anal fistula is simple but determining an internal opening is a challenging task. So, the doctor recommends a rectal examination to locate the internal opening.

Rectal Examination:

A rectal examination is performed by inserting a finger covered with a glove and lubricated gel into the anus and rectum to determine:

  • The functioning of the sphincter muscle
  • Area of infection
  • Extension of fistula

Other Diagnostic Tests for Anal Fistula:

Further diagnostic tests are performed to provide appropriate treatment. These tests include:

  • Proctoscopy uses a specialized telescope fitted with a light or a fistula probe (a small instrument inserted through the fistula) to see inside the rectum. It is generally performed under general anesthesia.
  • Anal Endosonography (a.k.a Anal Ultrasound) is a safe procedure that uses high-frequency sound waves for capturing images beneath the surface of the anal canal.
  • Magnetic Resonance Imaging (MRI) Scan uses a powerful magnetic and radio waves to create detailed images of the organ and is usually used in complex or reoccurring fistulae.
  • Computerized Tomography (CT) Scan combines a series of X-ray and a computer to create detailed cross-sectional images of the body, which may also help in evaluating the extent of the inflammation.

Treatment for Anal Fistula:

The treatment for anal fistula depends on the complexity and strength of the sphincter muscles. There are no medications to cure the condition, so surgical procedures are performed that include:

  • Fistulotomy is a most common and effective surgical procedure performed to open and drain an anal fistula.
  • Seton Techniques are performed by inserting a piece of thin surgical thread inside the fistula tract that allows the fistula to drain and heal completely.
  • Advancement Flap Procedure is performed if the fistula passes through the anal sphincter muscles. In this procedure, the hole of the fistula is covered, so that the fistula can heal.
  • Fibrin Glue or Collagen Plug is a non-surgical procedure for treating anal fistula. In this procedure, the surgeon injects special glue under the influence of general anesthesia, which seals the fistula and encourages healing.

Post-surgical complications of anal surgery include:


Infection is the most common complication after any surgery. The infection can be severe and may spread to different parts of the body. In some cases, the patient is hospitalized for providing proper treatment.

Bowel Incontinence:

Bowel Incontinence (a.k.a Faecal Incontinence) rarely occurs due to the damage of anal sphincter muscles, which leads to the leakage of faeces from the rectum. The likelihood of incontinence is based on the position of the fistula and type of surgery performed.

Recurrence of the Anal Fistula:

In some cases, anal fistula can recur even after surgery. The recurrence mainly depends on the type and complexity of the surgery.

Prevention of Anal Fistula:

An anal fistula can be prevented by following certain steps, such as:

  • Drinking plenty of fluids
  • Eating a fiber-rich diet
  • Keeping the anal region dry
  • Avoid straining while passing stools
  • Exercising regularly

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