Anal Fistula and Treatment

What is an Anal Fistula?

An anal fistula is an abnormal tract connecting the anal canal to the perianal skin. In most cases, it results from the progression of an anal abscess. Patient history often reveals spontaneous or surgical drainage of an abscess. However, it can also develop spontaneously or as a side effect of infectious, traumatic, inflammatory, or neoplastic diseases affecting the anorectum. Normally, Hermann and Desfosses glands play a crucial role in stool elimination by producing lubricating mucus in the small cavities of the anus called "anal crypts." However, when a microorganism enters these glands and blocks the mucus drainage canal, an infection can develop. This infection then spreads to the surrounding tissues and forms a channel connecting the anal gland (source of the abscess) to the skin of the perianal region. If the skin tears, a fistula forms and communicates with the outside.

Anal Fistula: What are the most common types?

Anal fistulas are classified according to their course in relation to the sphincters:

• Superficial anal fistula (16%): When the course is median with respect to the sphincters and does not cross any part of them;
• Intersphincteric anal fistula (56%): When the passage is located between the internal sphincter and the external sphincter;
• Transphincteric anal fistula (21%): If the passage crosses both the internal sphincter and the superficial or deep external sphincter to enter the ischioanal fossae;
• Suprasphincteric anal fistula (4%): If a component of the intersphincteric canal follows a course above the puborectal muscle and in any case below the levator plane;
• Extrasynthetic anal fistula (3%): When there is a direct connection between the perineum and the rectum without involvement of the anal canal;

In recent years, there has been a significant improvement in the accuracy of topographic diagnosis of anal fistulas thanks to the use of techniques such as endoanal ultrasound and magnetic resonance imaging (MRI).

What are the causes and risk factors associated with anal fistula?

Anal fistulas can be triggered by various factors, the same ones that cause anal abscesses:

• Anal ulcers;
• Inflammatory bowel diseases, such as Crohn's disease, diverticulitis, and ulcerative colitis. It is estimated that nearly half of people with Crohn's disease have an anal fistula at least once;
• Impaired immune system: It is important to note that nearly 30% of people with HIV may suffer from anal fistulas due to an impaired immune system;
• Rectal cancer;
• Tuberculosis;
• Sexually transmitted diseases (e.g., chlamydia and syphilis);
• Complication of intestinal surgery;

It is noted that men are more prone to developing anal fistulas than women. Medical data confirms this trend, revealing a higher prevalence among young adult men aged 20 to 40.

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How is the diagnosis of anal fistula made?

Anal fistula causes intense pain in the perianal region, which is even more painful during defecation, and may also be accompanied by fever. Often, the patient notices the discharge of pus at the level of the perineal swelling, which is painful, warm, and reddish. If the abscess process becomes chronic (with a softer and more localized swelling), these symptoms may disappear temporarily, only to reappear weeks or even months later. A fistula can be characterized by a purulent discharge (constant or intermittent) from a skin orifice, resulting in a decrease in pain. A satellite inguinal lymphadenitis may be associated. The skin surrounding the external orifice is indurated. The orifices may be multiple due to secondary pathways.

What are the surgical treatments for anal fistula?

Fistulotomy

Fistulotomy is typically reserved for patients with simple fistulas; this procedure consists of literally flattening the canaliculus. The procedure does not carry a significant risk of incontinence.

Fistulectomy

Fistulectomy consists of dissecting the entire fistula and a micro-portion of the surrounding healthy tissue.

Seton

A seton is a type of thick thread (small tube) inserted into the fistula and then connected at both ends to the outside of the body. The seton has two potential advantages. The first is the continuous drainage of material contained in the fistulous tunnel (such as pus), which escapes to the outside, avoiding the development of complications and facilitating subsequent surgical operations. The second advantage concerns the possibility of periodically putting the elastic in traction to slowly dissect the muscle tissue, incising a new segment as the previous lesion heals. In this way, sharp cuts are avoided and the risk of incontinence is reduced.

Two-stage fistulectomy

As the term indicates, this operation is performed at two different times in order to minimize the risk of complications, such as damage to the anal sphincter and fecal incontinence.

Fistula closure with fibrin glue

The procedure has a modest cure rate, in the order of 20 to 60%. It consists of injecting a soluble mixture inside the fistulous tunnel, after thorough cleaning (debridement), in order to effectively seal it, as glue would do. The advantages of this method lie in its low invasiveness, which eliminates most of the common complications of traditional surgical procedures (such as incontinence), while ensuring a quick return to daily activities. However, there is a high risk of recurrence and the success rates for complete healing of anal fistulas remain low.

LIFT technique

The LIFT technique is a new surgical procedure that aims to safely close the internal duct of anal fistulas (using the intersphincteric space rather than the endorectal route) while simultaneously removing the infected tissue at the origin of these fistulas. This minimally invasive, reliable, and affordable method is relatively new, with high success rates and a low risk of recurrence.

What are the risks associated with anal fistula?

It is rare, but it can happen, that an anal fistula heals spontaneously by transforming the granulation tissue of the fistulous passage into scar tissue, with obliteration of the lumen. In the case of a superficial fistula, the passage is covered with squamous epithelium from the orifices, with closure of the lumen. In general, if left untreated, the fistula persists indefinitely with continuous secretion. Cases of neoplastic transformation have also been described as a late complication of an untreated anal fistula.

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