The initial management of a fistula is to drain it. This is a small surgical procedure performed under general anaesthetic where a silastic seton similar in size and consistency to a rubber band is passed through the fistula tract and tied in place. This allows any pus to drain, and inflammation to settle figure 1.
A course of antibiotics may also be required. Within 6 weeks, the condition should be much improved, and you will need to be re-examined by a colorectal surgeon. There are 5 options at this point which include:.
This is best done before 6 weeks, as waiting longer than this can result in the formation of skin epithelium within the fistulous tract which can prevent its spontaneous closure. If the fistula tract involves a significant proportion of the anal sphincter muscle, it may not be safe to lay open the fistula tract, as that would involve cutting too much of the anal sphincter muscle, and this could potentially result in some degree of faecal incontinence.
Therefore, the seton may be left in place awhile longer or even indefinitely. This ensures further drainage of any abscess and settling of inflammation. Sometimes a loose seton is re-tightened until it is snug with the aim of slowly cutting through the anal sphincter muscle tight cutting seton.
With repeated tightening, the seton slowly lays open the fistula tract, with the seton eventually falling out on its own without need for incising the anal sphincter. This slow process can take up to a year. Occasionally, the seton eventually works its way out without the need for tightening loose cutting seton , with the seton slowly cutting through the anal sphincter muscle.
However, this can take years, but is safer than a tight cutting seton, as the sphincter has time to heal and repair itself as the fistula tract is slowly laid open[6]. If the seton involves less than a third of the internal anal sphincter muscle, then it may be reasonable to remove the seton by laying open the fistula tract and cutting the overlying muscles.
This allows cleaning curetting of the fistula tract, to promote its healing. If the seton involves a large amount of anal sphincter, the seton may be removed, and a formal excision of the fistula tract performed. This is an operation best performed after 12 weeks or even longer , to allow complete resolution of sepsis and the formation of a definite epithelial-line or fibrous fistula tract that is well defined and therefore easier to surgically remove.
This may involve simple ligation and excision of a portion of the fistula tract, without the use of a flap i. LIFT procedure or may involve excision of the entire length of fistula tract followed by a formal flap repair to cover the internal opening. If the internal opening is high in the anal canal a rectal advancement flap is performed using a flap of mucosa and the underlying muscle to cover the internal opening. If the internal opening is low in the anal canal, an anoderm V-Y advancement flap may be preferable.
Both these flap repairs also involve repairing the sphincter, and cleaning curetting the external opening to allow ongoing drainage until the repair has healed. A vast number of plugs and glues have been used to try to seal fistula tracts.
The benefit of these techniques is that they preserve the anal sphincters. Initial results with fibrin glue were promising. Several products are commercially available and treatment involves single or repeated injection into the external opening. Treatment of an anal fistula is attempted with as little impact as possible on the sphincter muscles. It will often depend on the fistula's location and complexity, and the strength of the patient's sphincter muscles.
In a fistulotomy the surgeon first probes to find the fistula's internal opening. Then the tract is cut open and is scraped and its contents are flushed out, then its sides are stitch to the sides of the incision in order to lay open the fistula. A more complicated fistula, such as a horseshoe fistula where the tract extends around both sides of the body and has external openings on both sides of the anus , is treated by usually laying open just the segment where the tracts join and the remainder of the tracts are removed.
The surgery may be performed in more than one stage if a large amount of muscle must be cut. The surgery may need to be repeated if the entire tract can't be found.
A surgeon may core out the tract and then cut a flap into the rectal wall to access and remove the fistula's internal opening then stitches the flap back down. This is often done to reduce the amount of sphincter muscle to be cut. In some cases, fibrin glue, made from plasma protein, may be used to seal up and heal a fistula as opposed to cutting it open.
The glue is injected through the external opening after clearing the tract and stitching the internal opening closed. A plug of collagen protein may also be used to seal and close the fistula tract. Anal Fistula Anal fistulas are generally common among those who have had an anal abscess.
In order of most common to least common, the various types include: Intersphincteric fistula. The tract begins in the space between the internal and external sphincter muscles and opens very close to the anal opening. Transphincteric fistula. The tract begins in the space between the internal and external sphincter muscles or in the space behind the anus.
It then crosses the external sphincter and opens an inch or two outside the anal opening. These can wrap around the body in a U shape, with external openings on both sides of the anus called a horseshoe fistula.
Suprasphincteric fistula. The tract begins in the space between the internal and external sphincter muscles and turns upward to a point above the puborectal muscle, crosses this muscle, then extends downward between the puborectal and levator ani muscle and opens an inch or two outside the anus.
Extrasphincteric fistula. The tract begins at the rectum or sigmoid colon and extends downward, passes through the levator ani muscle and opens around the anus. These fistulas are usually caused by an appendiceal abscess, diverticular abscess or Crohn's disease.
Diagnosis It is usually simple to locate the external opening of an anal fistula, meanwhile locating the internal opening can be more challenging. Tools often used in diagnosis include: Fistula probe. An instrument specially designed to be inserted through a fistula Anoscope.
A small instrument to view the anal canal If a fistula is potentially complicated or in an unusual place, these tools may also be used: Diluted methylene blue dye. Injected into a fistula Fistulography. Injection of a contrast solution into a fistula and then X-raying it Magnetic resonance imaging Tools used to rule out other disorders such as ulcerative colitis or Crohn's disease include: Flexible sigmoidoscopy.
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