3 Mount Elizabeth, #14-15, Mount Elizabeth Medical Centre, Singapore 228510

Anal Fistula

Anal Fistula

What is an anal fistula?

An anal fistula, also known as a perianal fistula, is an abnormal tunnel-like canal that forms between the inside of the anus and the skin surrounding the anus. Anal fistulas can be a source of extreme discomfort and pain, depending on the type. 
Anal fistulas are typically classified based on their location:
  • Intersphincteric fistula: interspincteric fistulas are the most common type of anal fistula. It is characterised by the formation of a tunnel between the inner muscle of the anus (sphincter muscle) and the skin on the outside of the anus.
  • Transphincteric fistula: transphincteric fistulas occur when the tract starts in the space between the internal and external sphincter muscles or the space behind the anus. As it progresses, the fistula then crosses the external sphincter and opens an inch or two outside the anal opening.
  • Suprasphincteric fistula: suprasphincteric fistulas occur when the tract starts in the space between the internal and external sphincter muscles. Then, it turns upward to a point above the puborectal muscle. The fistula then crosses this muscle, extends downward between the puborectal and levator ani muscle, and opens an inch or two outside the anus.
  • Extrasphincteric fistula: extrasphincteric fistula is where the tract starts at the rectum or sigmoid colon. It then extends downward, passes through the levator ani muscle, and opens around the anus.
  • Submucosal fistula: submucosal fistulas are not typically classified with the standard type of anal fistulas listed above. It runs beneath the submucosal layer of the gastrointestinal tract and is less complex than other types of anal fistulas.
    • Anal fistula can induce a lot of pain and discomfort for those affected.

    What causes anal fistulas?

    An anal fistula typically starts when an anal gland becomes infected and blocked, forming an anal abscess. Rather than breaking back into the anus, the infection breaks through the skin and creates a tunnel near the anus.
    Anal fistulas typically develop from complications of the following:

    Anal trauma or surgery:

    surgery or trauma near the anal region may lead to an infection and the formation of an abscess which can result in an anal fistula.

    Anal abscess:

    Anal abscess: anal abscesses occur when an anal gland becomes blocked and infected. If the abscess does not drain and heal completely, an anal fistula will form.

    Medical conditions:

    medical conditions such as irritable bowel syndrome (IBS), diverticular disease, tuberculosis, cancer, sexually transmitted diseases (STDs), and other types of infections can cause abscesses to occur along the gastrointestinal tract. This can lead to anal fistulas.

    What are the symptoms of an anal fistula?

    The symptoms of an anal fistula may include:
  • Passing blood or pus when excreating
  • Intense and throbbing pain in the anal region, especially during bowel movements
  • Foul odour from discharge at the anus
  • Irritation and redness inside or around the skin of the anus
  • Bowel or stool incontinence (link to service page) in extreme cases
  • Fever
    • If you are experiencing any symptoms stated above, make an appointment with Colorectal Care and Cancer Specialists today.
    People suffering from an anal fistula may experience significant pain when seated.

    Who is at risk of developing an anal fistula in Singapore?

    Some factors that may increase the likelihood of developing anal fistulas include:
  • Anal trauma/surgery:
    • a new traumatic injury to the anus or prior injury in the anus.
  • Gastrointestinal conditions:
    • individuals with gastrointestinal conditions such as inflammatory bowel disease (IBD) (link to service page) are more prone to developing anal fistulas.
  • Immunocompromised individuals:
    • individuals with conditions that compromise their immune system, such as HIV, are more prone to infections which may lead to anal fistulas.
  • Infections:
    • history of bacterial infections such as actinomycosis, tuberculosis, and sexually transmitted infections (STIs).
  • Prior treatments:
    • such as radiation therapy for the pelvic region or surgery in the anal area (such as drainage of perineal abscess) could increase the risk of anal fistula formation.
  • Gender:
    • men are more prone to anal fistula compared to women.
    These risk factors increase the pressure and strain on the anus, which can cause tears in the lining, resulting in an anal fissure.
    A digital rectal exam may be necessary when diagnosing for anal fistulas.

    How are anal fistulas diagnosed?

    Anal fistulas are diagnosed with one or a combination of the following procedures:

    Medical history and physical examination:

    your doctor will inquire about your medical history to determine the probable cause of your anal fistula. The area will be examined to check for blood or pus, which may indicate the anal fistula’s opening.

    Anoscope:

    an anoscope is a scope that is often used to look inside the anal canal to determine the presence of fistulas.

    Digital rectal exam:

    a digital rectal exam will be conducted to check for abnormalities characteristic of anal fistulas.

    Fistula probe:

    a fistula probe is a long, thin probe guided through the other opening of the fistula. Additionally, a dye may be injected to help doctors see where the fistula begins and ends.

    Imaging studies:

    imaging studies, such as an ultrasound, are used to create images of the anal to help doctors look for the presence of fistulas.

    Examination under anaesthesia:

    this benchmark diagnostic procedure aids in accurately diagnosing and classifying anal fistulas without causing any pain to the patient.

    What are the treatment options for anal fistulas in Singapore?

    The only treatment for anal fistulas is surgery. As such, there are various types of surgeries available to treat anal fistulas; these include:

    Fistulotomy:

    a fistulotomy is the most common treatment for anal fistulas. It involves opening the length of the anal fistula and allowing it to heal from the inside out. However, this procedure is only suitable for fistulas that do not pass through any anal sphincter muscles.

    Advancement flap procedure:

    an advancement flap procedure is used for more severe anal fistulas. It involves removing part of the rectal wall and using it to block the opening of the anal fistula.

    Seton techniques:

    setons are flexible threads that are placed in the anal fistula tunnel to keep it open. This prevents abscess formation during healing.

    Fibrin glue/plugs:

    fibrin glue can be injected into the fistula and seal it shut. Like fibrin glue, fibrin plugs can be inserted into the fistula to block it.

    Frequently Asked Questions

    Although anal fistulas are not life-threatening, they can lead to severe complications such as systemic infections, which can consequentially compromise your immune system. Additionally, after a prolonged period, you are at higher risk of issues such as bowel incontinence which will significantly impact your quality of life. In worst-case scenarios, untreated, anal fistulas can develop into anal cancer as a result of chronic inflammation.

    The leading cause of a fistula, particularly an anal fistula, is usually an anal abscess that hasn't healed properly or completely.

    No, they do not. Anal fistulas require prompt medical intervention to prevent future complications.

    Recovery from anal fistula surgery can vary depending on several factors, including the type of surgery performed, the complexity of the fistula, the patient's overall health, and how well post-operative instructions are followed. Recovery ranges from four weeks to several months.

    Yes, anal fistulas can recur.

    Anal fistulas are tunnel-like canals, whereas anal fissures are cracks or tears that form in the tissue of the anus.

    Location

    Colorectal Care Specialists (CRCS)

    3 Mount Elizabeth, #14-15, Mount Elizabeth Medical Centre, Singapore 228510

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