7 key questions about anal fistula

What is an anal fistula?

It is an abnormal communication between the inside of the anus and the outer perianal skin.

Anal fistulas are three to seven times more common in men than in women and, although very infrequently, also occur in children.

Anal fistula is the most complex and difficult to treat benign pathology of the anus.

What are the causes of anal fistula?

Inside the anal canal there are glands that produce mucus to lubricate the area, so that when stool comes out it does not cause injury to the anus.

Except for anal fistulas secondary to Crohn’s disease and ulcerative colitis, all other anal fistulas are due to infection of one of these anal glands.

When one of these glands becomes infected, it becomes obstructed. The resulting pus seeks a new outlet to the perianal skin, leading to the appearance of an anal fistula.

What types of anal fistulas are there?

There are multiple ways to classify a fistula but here we are going to simplify it by classifying them in relation to the anal sphincters. These sphincters (internal and external) are two circular muscles that surround the anal canal and are responsible for the continence of stool and gas. The different types of fistulas are:

  • Subcutaneous or submucosal fistula: the path passes under the skin or mucosa of the anal canal. It does not affect the sphincters.
  • Intersphincteric fistula: the tract passes through the space between the two sphincters.
  • Trans-sphincteric and extra-sphincteric fistula: the tract passes through both anal sphincters.
  • Suprasphincteric and extrasphincteric fistula: these are two types of very complex fistulas whose fistulous tracts pass over the two sphincters.
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What symptoms can we identify?

  • Acute phase (abscess): characterized by the appearance of a painful, red and warm lump at the anal margin (abscess), with malaise and fever. The patient cannot sit up and has difficulty walking. The abscess may open spontaneously or require surgical opening to evacuate the pus and relieve symptoms.
  • Chronic phase (fistula): one or more orifices appear in the perianal skin, intermittently draining a purulent or bloody discharge. This discharge irritates the skin causing itching and itching. There may be new episodes of inflammation which generally cause the fistulous tract to branch out, complicating the disease and the treatment.

How is the diagnosis made?

The patient’s history of suppuration already makes us suspect the existence of an anal fistula.

A detailed physical examination is then performed. Visual examination of the area identifies the external perianal orifice. Gently, a rectal examination is performed to palpate the fistula trajectory and the internal orifice, as well as its relationship with the anal sphincters, which is of vital importance to decide the surgical treatment.

The examination is completed with an ano-rectoscopy. In some rare cases a pelvic MRI or endoanal ultrasound may be required.

How is an anal fistula treated?

Treatment is always surgical and must meet two basic objectives:

  • Eliminate all fistulous tracts.
  • To preserve the integrity of the anal sphincters, maintaining their normal function.

Throughout history a multitude of techniques have been described and depending on the different surgical schools, one or the other is performed. In our center we perform the following:

  • Fistulotomy with CO2 laser: consists of canalizing the fistulous tract with a metallic probe and cutting the tissue that remains above the probe with the CO2 laser. This technique is used in submucosal and intersphincteric fistulas.
  • Setton loose: this technique was described by Hippocrates in 400 BC. It consists of placing an elastic line in the fistulous tract. We only use this technique as an intermediate step for definitive surgery. We will use it in case of abscessed fistulas.
  • Intersphincteric fistulectomy with CO2 laser: this technique was introduced in Spain by Dr. Diaz Yanes in 1996. It consists of the complete removal of the fistulous tract without cutting the anal sphincters and then closing the orifices through which the fistula passed. In this way we manage to preserve the anal sphincters intact and therefore their function. This technique is used in complex fistulas.
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What are the advantages of CO2 laser treatment?

We perform these surgical techniques with CO2 laser because it allows us to:

  • Identify with certainty the internal and external anal sphincter.
  • Highly hemostatic and painless.
  • Early hospital discharge, in a few hours.
  • Rapid healing.
  • Return to normal life in 24-48 hours.