Anal fistula

Anal fistula is a pathological connection between the skin of the perineum and the rectum or anal canal. It occurs 8 times more often in men than in women. The total prevalence is about 7 / 100,000 people. The average age is 40 years.

Etiology
In the area of the rectum and dam, there are also fistulas that may not be related to the rectum (from the female genitalia, urethra, prostate). Those that come from anal landscape and rectum can be divided into congenital and acquired.
 * Congenital fistulas – are part of anomalies in rectal development.
 * Acquired fistulas:
 * – 80–90 % arises on the basis of periproctal abscesses caused by infections of the anal glands (so-called cryptoglandular theory).
 * – 10–20 % have a different etiology: dermoid cyst, perineal trauma, Crohn's disease, pelvic inflammation, TBC, carcinomas, radiation therapy, actinomycosis, chlamydial infections, or other sexually transmitted diseases.


 * Rare fistulas – the horseshoe-shaped fistula has long side trunks surrounding the anal canal, most often it is transsphincteric. If unrecognizable, it often relapses.

Divisions
Fistulas can be divided according to their relationship to the rectum - rectal and periproctal (perianal). Furthermore, we divide them into complete and incomplete according to whether they have external and internal orifices (complete) or only one (incomplete, more often external). A complex (complicated) fistula is one whose inner mouth extends above the puborectal muscle or its tract surrounds more than 3/4 of the external sphincter.

According to the anatomical position of the tract, we divide fistulas into:
 * intrasphincteric (subcutaneous, submucosal),
 * intersphincteric,
 * transsphincteric,
 * extrasphincteric.

According to Parks (intrasphincteric, transsphincteric, suprasphincteric, extrasphincteric).

Symptoms
Fistulas are manifested by secretion, itching and wetting of the surrounding, contamination of the laundry with stool or pus. The pain occurs when the contents stagnate when the drainage stops. Swelling and bleeding, feelings of fullness and pressure in the rectum may also occur. Subfebrile symptoms may also occur. It is common to alternate asymptomatic periods with symptomatic periods of various lengths of time. The internal fistula may not appear clinically at all.

Diagnostics
Significant is a thorough anamnesis with a focus on anorectitis and abscesses in this area in the past, the search for symptoms of Crohn's disease. Physical examination is of the greatest importance:
 * Aspection – we find the outer mouth of the fistula. Fistulas may have multiple external orifices, but usually have only one internal orifice. The distance from the anus can tell us what type of fistula it is. Closer to the anus - rather subcutaneous, further from the anus - more complicated fistula
 * Goodsall's rule – if we follow the transverse line, then the fistulas, whose outer mouth is dorsally from this line, run in arc and have an inner mouth at No. 6 (middle back line). Fistulas that have an external oral ventral lead straight and open radially to approximately the same position. But Goodsall's rule does not apply to 100%, there are more deviations for women.
 * Palpation – you can feel stiffer stripe, induration in the surroundings. During the per rectum examination, we can sometimes feel the inner mouth.
 * Anoscopy, rectoscopy, colonoscopy – allows you to evaluate the rectal mucosa, location of the internal oral fistula, tumor exclusion or non-specific intestinal inflammation.
 * Fistula probing – we use a stick probe to determine the course of the fistula in a non-violent manner; If the inner mouth is unclear, we can use a solution of hydrogen peroxide, betadine, or methylen blue.
 * Fistulography – a contrast agent is used for fistulas in Crohn's disease, recurrence or complicated course. We will show the branching, the course and the blind trunks. However, the yield of the examination is low
 * US – endosonographic examination has recently been widely used and replaces CT examination, which is of little use for diagnosis. US can be used for primary diagnosis and perioperatively.
 * NMR – nuclear magnetic resonance is the most accurate method for imaging complicated fistulas, especially in Crohn's disease.

Treatment
History of fistula treatment dates back to antiquity. Hippocrates used already methods similar to today, threaded horsehair (seton) with fistulas, loaded with stones (cutting seton). The first comprehensive treatise on this issue dates from the 14th century (J. Ardern) and fistulas did not escape even the French King Louis XIV.

Conservative techniques:
 * In the past, conservative therapy with the application of sclerosing agents (eg AgNO3), was widely used, but for poor results, it is no longer used.
 * Today, various fibrin tissue adhesives are used, the most successful in treatment are tissue adhesives with intraadhesive ATBs.

Surgical techniques:
 * Fistulotomy, fistulectomy (lay open) – these similar procedures are performed on simple low fistulas without a complicated course. After clarification of the tract and internal orifice, a groove probe is inserted into the fistula and the fistula is dissected, the surrounding tissue is excised and the base is excochleated, and the tissue sample can be taken at histology. The wounds is left for secondary healing or marsupialization. During fistulectomy, excision is performed on the probe. However, these techniques have a larger tissue defect and a higher percantage of postoperative incontinence. Therefore, there are various modifications of operations to preserve the integrity of the external sphincter (Parks fistulectomy).


 * Seton technique – (Hippocratic elastic ligature, cutting seton) is a technique used in higher transsphincteric, extra- and suprasphincteric fistulas. After identification of the outer and inner oral, the non-absorbable, best elastic fiber (silicone, rubber) is threaded through the fistula and knotted under a slight pull. The fiber is gradually cut through the sphincter, it must be tightened to keep approximately the same modification. Healing lasts 6-8 weeks, fibrotic tissue gradually forms behind the cut fiber. The technique can be performed subcutaneously in modification. Indications must be considered, there is a greater risk of incontinence in ventral fistulas in women.
 * Seton drainage is used for complex, multiple fistulas, and fistulas in Crohn's disease. This technique is similar, but the fiber is fistula introduced loosely without tension. Inelastic materials can also be used. Thanks to seton drainage, the fistula gradually matures, followed by its excision. In Crohn's disease, tracing ligatures are used for long-term (weeks to months) drainage of fistulas with abscesses.


 * Mucosal sliding flap (advancement flap) – has the best results, can be used with almost all types of fistulas, is advantageous for complicated fistulas. Healing is preferably per primam. Does not cause anal deformities. the method consists of a fistulectomy outside the sphincters, an excision of the inner mouth, which is followed by the construction of a sliding musocal tube, which is pulled into the defect and mixed with sutures around the circumference. The external defect is left to secondary healing.


 * Anal fistula plug – the use of special biological anal plugs that allow the fistula to heal.

New operating techniques:
 * LIFT – Ligation of the Intersphincteric Fistula Tract – a new, relatively simpler technique of intersphincteric ligation.
 * VAAFT – Video Assisted Anal Fistula Treatment – endoscopic examination of the fistula tract (fistuloscpy) with visualization of branching and possibility of internal oral treatment using a stapler or cutter.
 * Fistula coagulation using RFA or laser.

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