Anal fistulae: what they are, symptoms and causes - THDLAB - COM

  • What are anal fistulae
  • Anal fistulae: symptoms
  • Anal fistulae: causes and risk factors

What are anal fistulae

Anal fistulae are lesions which manifest as an orifice in the anal canal and the other usually on the surface of the perianal skin. In most cases, pus, blood and serum leak from this small hole. Anal fistulae are often caused by infections in the anorectal region or by other diseases. Most fistulae connect the inner part of the anal canal with the perineum.


Anal fistulae: symptoms

The symptoms of anal fistulae are local pain, swelling and irritation. These symptoms tend to increase during defecation. Fistulae can also manifest with serous and purulent leaks through the external orifice near the anus and cause fatigue, pelvic pain and fever.


Anal fistulae: causes and risk factors

Fistulae are classified according to their location and to the relationship with the sphincter muscles. There are 5 types of anal fistulae, but the most common are: superficial, intersphincteric and transphincteric fistulae.

Anal fistulae can originate from various diseases and infections of the anorectal region. Anal fistulae are often the evolution of an anal abscess which reaches the skin around the anus.

The anal or perianal abscess is a collection of pus linked to an inflammatory process triggered by an infection.

Often, the abscess and the perianal fistula are two different stages of the same disease. The abscess is the acute phase of an infection which starts from the glands of the anal canal. The fistula is instead the infectious process which becomes chronic and often forms 4-6 weeks after drainage of the pus.

Therefore, the onset of an anal fistula is favoured by the same factors which can cause the onset of an anal abscess, including:

  • inflammatory bowel disorders
  • weakened immune system
  • anal ulcers
  • sexually transmitted diseases
  • post-operative complications
  • rectal cancer

The disorder can also originate from an anal fissure which is not recognised or is neglected and which then becomes infected, evolving into a fistula.