I. Concept
Anorectal fistula is a fistula formed when a perianal abscess breaks down or the pus cavity gradually shrinks after incision and drainage.
It is difficult to define a complex fistula, but the Clinical Guidelines for the Management of Anal Fistula (2006 edition) defines a complex fistula as a fistula that crosses more than 30-50% of the external sphincter (between the high sphincter, above the sphincter, or outside the sphincter), multiple fistulas, recurrent fistulas, or fistulas with anal incontinence that may cause anal incontinence after treatment.
II. Etiology
Primary anal fistulae originate from septic infection of the saphenous glands, which spreads between the internal and external sphincters and enters the perianal space, or the perirectal space or the colorectal fossa. It is thought that 95-97% of anal fistulas are caused by infection of the anal glands.
Secondary fistulas are most often caused by systemic diseases such as Crohn’s disease, ulcerative colitis (UC), polypustular sweat glands, tuberculosis, Hiv/AIDS, actinomycosis, leukemia, sacrococcygeal teratoma, intra-abdominal or pelvic disease, tumors, trauma, etc. About 40% of Crohn’s disease has anorectal manifestations.
Recurrence can be caused by misjudgment of the primary fistula (main tube) during surgery, neglect of the branched tube, omission of the true internal orifice, and inappropriate surgery due to the surgeon’s fear of damaging the sphincter, which can eventually lead to CAF.
C. Classification
CT scan photography: useful for deep perirectal abscesses, but poor resolution of soft tissues, cannot show the anal levator and sphincter, and is not significant for the diagnosis of anal fistula.
Magnetic resonance imaging (MRI): Intracavitary MRI is a new technique for the diagnosis of CAF, with multi-planar, multi-volume and high resolution, which can accurately depict the anatomy of the internal and external anal sphincter, anal levator, puborectalis muscle and show the relationship between anal fistula and perianal muscles and make a correct assessment of the postoperative outcome. It is an excellent complement to EAUS.
Anorectal manometry (MAP), which accurately measures anal muscle tone, rectal compliance, anorectal sensation and anorectal inhibition reflexes, provides pathophysiological data before and after anal fistula surgery by means of resting and systolic pressures, which helps in the selection of surgical approach and in determining the extent of postoperative sphincter damage, and TSF detects a decrease in anal resting and systolic pressures due to the incision of both the internal and external sphincters, Approximately 53% to 57% of patients have mild incontinence, which can be treated with medication and biofeedback, while severe damage requires repair.
The following points should be noted during surgery:
1, the search for the internal opening is accurate. The endoguchi of anorectal hoof-shaped abscess is mostly near the 6-point dentate line in the truncated position or with reference to Solomons’ law.
2, intraoperative blunt separation of the interval, anorectal hoof-shaped abscess is easy to spread to the surrounding spaces, the interval is difficult to blunt separation of each gap can also be hung in layers of rubber band to drain.
3.When changing medicine, the wound is separated by Vaseline gauze to ensure that it will not heal bridgingly.
4.Refer to the drug allergy effective choice of antibiotics. Before, broad-spectrum antibiotics or antibiotics against G-bacteria can be used.5 If the efficacy is not satisfactory, tuberculosis or atopic infection and mixed infection should be considered, and diagnostic treatment can help in some cases.
Postoperative management
Avoid spicy food and alcohol, eat more vegetables, and keep stools soft to prevent constipation. Take a daily sitz bath with 1:5000 potassium permanganate solution in warm boiling water. Each time 15-20min, 3-7 times a day, oral antibiotics to prevent infection.
Because of the variable route of complex anal fistula, varying depths and curvatures, there is often no fixed pattern for surgery to follow.
How to prevent
In the past, for the treatment of anorectal abscesses, most of them were treated by incision and drainage, and if an anal fistula was formed six months to one year after the wound healed, the second stage of the operation would be hung, which was a long treatment time, relatively painful for the patient and relatively expensive. After many years of summary of our hospital, for anorectal abscess comprehensive abscess incision and drainage + fistula hanging method, the use of multiple incision segmental hanging line therapy, the efficacy is satisfactory.
The rubber band is taken from the edge of the disposable glove leather band, which is flexible, with less local tissue reaction and easy to clean. The perianal radial incision is made at 3-5 cm intervals, and the rubber band is used for drainage, which is easy to observe. After the inflammation subsides, the wound is filled with growth while draining, leaving no dead space. By transferring the external opening, the incision is made at the closest part of the internal opening and hung with the internal opening, the skin, muscles and ligaments are less damaged, the anus is not deformed, and the function of the anus is rarely damaged.