Anal fistula: definition and diagnosis


What is an anal fistula?

A fistula, in general, is a nonphysiological, that is, not “natural” communication between two surfaces lined by epithelial tissue. It is a channel that communicates two structures, or a structure to the skin. They can be of various types and be located in various places of our body, and their causes and treatments vary greatly depending on all of these factors.

An anal fistula is an abnormal communication that is established between the external region around the anus, or perianal region, and the anal canal, internally.

Causes of anal fistula

Anal fistulas usually originate in the anal canal, internally, from local inflammation, usually from a gland, which causes an abscess – or accumulation of pus – which, after drainage, generates an orifice externally. The fistula is characterized by the perpetuation of a path that connects the infected gland and the orifice from the resulting abscess drainage. This communication can also be generated between the anal canal and another internal organ, such as the vagina, for example.

This process of anal fistula formation is usually quite painful, and may be accompanied by fever and chills. Drainage of the abscess may occur spontaneously, or there may be a need for surgical drainage performed by a specialized coloproctologist. If the underlying disease is not treated, healing of the drainage orifice is not complete, leading to the fistula, which tends to occur in one in three patients after a perianal abscess.

Other less frequent causes of anal fistula include tuberculosis, inflammatory bowel disease, anorectal traumas, rectal or anal canal neoplasms, rectal surgeries, gynecological, obstetrical and infectious diseases, such as lymphogranuloma venereum. Anal fistulas arise randomly in both sexes, at any age. In children, anal fistulas are rare.

Symptoms of Anal Fistula

Once the anal fistula is installed, the most common symptoms are pain in the anal region, presence of purulent secretion in the region near the anus, sometimes accompanied by bleeding or a liquid of chocolate-like appearance. Symptoms tend to improve with drainage, or the patient may notice a temporary closure of the fistula, with subsequent reopening, in the same location or in close proximity, and return of symptoms. Fistulas can exist for a long time without generating symptoms.

Diagnosis of Anal Fistula

The diagnosis of anal fistula is essentially clinical, that is, based on the patient’s symptoms and physical examination. Remembering that it is also fundamental to do the diagnosis of the causal factor of the infection that originated the fistula. It is also important to differentiate fistulas from other diseases and infections that affect the anal canal, such as dermatitis, folliculitis, boils and hidradenitis suppurativa.


The treatment of anal fistulas is surgical, since a fistula scarcely heals permanently once established. The clinical treatment alone is not sufficient for its cure.

There may be a need for administration of antibiotics in addition to surgical treatment in selected cases, such as in diabetic and immunosuppressed patients (such as those transplanted). It is also necessary to treat the infection that first generated the fistula, and the treatment will depend on each case.

The surgical technique employed will depend on each type of fistula, especially the path of it in the body. To define the characteristics of the fistula and its course, an image examination is usually performed, such as ultrasonography of the anal canal.

One of the most important consequences of treating anal fistulas is fecal incontinence. Therefore, in the presence of doubts during the clinical evaluation of anal fistulas, the function of the anal canal before surgery – especially with regard to muscle function – should be clarified through anorectal electro manometry.

Both of the above highlighted assessments can be made shortly before the surgery in order to get a current picture.
Of the most common surgical techniques for the treatment of anal fistulas, the following stand out:

  • Anal fistulotomy at one time: it consists of the identification, opening and curettage, or scraping of the path of the fistula. It is the most commonly performed.
    Two-stage anal fistulotomy: a procedure similar to the previous one, with the addition of the passage of a seton (or sedentem), a flexible material introduced throughout the fistula path, aiming to reduce the occurrence of fecal incontinence after surgery.
  • LIFT, or “intersphincteric ligation of the fistulous path”: a sphincter-sparing technique in which the path of the fistula is identified, attached or “tied” between both sphincters, without being severed. The inner and outer holes are also treated.
  • Use of Filling Substances: filling the path of the fistula with fibrin glue, or, more recently, with a material called Surgisys. Although they generated great expectations when they were described, both techniques are in disuse due to the disappointing results.
  • VAAFT – or Video-assisted Treatment of Fistula Path: described in 2011 by Meinero and collaborators, in Italy, uses optical equipment connected to a micro video camera, which enables not only the identification of the fistulous path, but also its approach and treatment. It can be associated with LIFT as a way to get better results.

At Colono, we have professionals specialized in the detection of anal fistulas. All the exams mentioned, as well as all the techniques currently available, including the most modern sphincter-sparing techniques are at your disposal. Schedule your appointment now!

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