Anal fistula


Anal fistula is a chronic abnormal communication between the epithelialised surface of the anal canal and usually the perianal skin. An anal fistula can be described as a narrow tunnel with its internal opening in the anal canal and its external opening in the skin near the anus. Anal fistulae commonly occur in people with a history of anal abscesses. They can form when anal abscesses do not heal properly.
Anal fistulae originate from the anal glands, which are located between the internal and external anal sphincter and drain into the anal canal. If the outlet of these glands becomes blocked, an abscess can form which can eventually extend to the skin surface. The tract formed by this process is a fistula.
Abscesses can recur if the fistula seals over, allowing the accumulation of pus. It can then extend to the surface again – repeating the process.
Anal fistulae per se do not generally harm, but can be very painful, and can be irritating because of the drainage of pus. Additionally, recurrent abscesses may lead to significant short term morbidity from pain and, importantly, create a starting point for systemic infection.
Treatment, in the form of surgery, is considered essential to allow drainage and prevent infection. Repair of the fistula itself is considered an elective procedure which many patients opt for due to the discomfort and inconvenience associated with an actively draining fistula.

Signs and symptoms

Anal fistulae can present with the following symptoms:
Diagnosis is by examination, either in an outpatient setting or under anaesthesia. The fistula may be explored by using a fistula probe. In this way, it may be possible to find both openings. The examination can be an anoscopy. Diagnosis may be aided by performing a fistulogram, proctoscopy and/or sigmoidoscopy.
Possible findings:
Depending on their relationship with the internal and external sphincter muscles, fistulae are classified into five types:
Other conditions in which infected perianal "holes" or openings may appear include pilonidal cyst.

Treatment

There are several stages to treating an anal fistula:
Definitive treatment of a fistula aims to stop it recurring. Treatment depends on where the fistula lies, and which parts of the internal and external anal sphincters it crosses.
LIFT Technique is a novel modified approach through the intersphincteric plane for the treatment of fistula-in-ano, known as LIFT procedure. LIFT procedure is based on secure closure of the internal opening and removal of infected cryptoglandular tissue through the intersphincteric approach. Essential steps of the procedure include, incision at the intersphincteric groove, identification of the intersphincteric tract, ligation of intersphincteric tract close to the internal opening and removal of intersphincteric tract, scraping out all granulation tissue in the rest of the fistulous tract, and suturing of the defect at the external sphincter muscle. The procedure was developed by Thai colorectal surgeon, Arun Rojanasakul, The first reports of preliminary healing result from the procedure were 94% in 2007. Additional ligation of the intersphincteric fistula tract did not improve the outcome after endorectal advancement flap.
Some people will have an active infection when they present with a fistula, and this requires clearing up before definitive treatment can be decided.
Antibiotics can be used as with other infections, but the best way of healing infection is to prevent the buildup of pus in the fistula, which leads to abscess formation. This can be done with a seton.

Epidemiology

A literature review published in 2018 showed an incidence as high as 21 people per 100,000. "Anal fistulas are 2–6 times more prevalent in males than females, with the condition occurring most frequently in patients in their 30s and 40s."