الفهرس 
Anatomy and embryology of the rectum and anal canalOnly 14 pages are availabe for public view
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Abstract
Fistula-in- ano is a track, lined by granulation tissue that connects deeply in the anal canal or rectum and superficially on the skin around the anus. Perianal fistula is characterized by chronic, purulent, malodorous, ulcerating, sinus tracts in the perianal tissue. The cryptoglandular hypothesis is the most accepted theory in its pathogenesis, also there are some other causes e. g Crohn’s disease, ulcerative colitis, actinomycosis, foreign body, lymphogranuloma venerium and trauma. the estimated incidence is about 1: 10. 000. most fistulae occur at the age of 30-60 years. The gender ratio in adults is (male: female) 2: 1 to 4: 1
In the standard classification of anal fistulae, the fistula is classified into two groups; low level fistulae in which the internal opening below the anorectal ring, and high level fistulae in which the internal opening at or above the anorectal ring, but the most widely used classification is that of park’s in which the anal fistulae are clssified into; inter-sphincteric, trans-sphincteric, supra-sphincteric, extra-sphincteric.
Radiological investigation have a limited role in evaluation of fistula in ano, most primary fistulae can be treated on the basis of clinical examination alone. However, when atypical features are present or when prior surgery has failed, radiological evaluation may be useful.
Fistulography can reveal the depth and the branches of the tracks. However, the injection of dye under high pressure carries the risk of sepsis dissemination.
With Three dimention endanal ultrasound, fistula tract is visualized as tube-like hypoechoic lesion, when hydrogen peroxide 3% is introduced into the fistula tract it generates small air bubbles, the ultrasonografic appearance is changed into bright hyperechoic. By comparing the tow images, the fistula tract and its extentions could be identified and discriminated from previous scars.
Pelvic magnatic resonance imaging is accurate in identifying perianal fistula, as it was shown that fistula surgery guided by MRI reduced the recurrence of anal fistula by 75% and therefore, recommended in all patients presenting with recurrent fistula. Performing MRI with contrast allows discrimination of fistulous tracts from adjacent structures.
Surgical strategies to treat anal fistula tend to be guided by their degree of complexity and their underlying aetiology.
For simple low fistula, fistulotomy and lay open may be enough. But for high anal fistula, seton fistulotomy provides good results. This method depends on tightening a seton which encircle the striated muscles that lie superficial to the fistula tract. The striated muscle is slowly divided by a process of ischaemic necrosis, this method in remarkably successful in preserving sphincter function.
Fistulectomy by core out technique is suitable for high anal fistula but not for recurrent or more complex fistula, rerouting method has the benefit of minimal loss of muscle tissue but it is technically difficult and necessitates more than one sitting
Electrocauterization is a simple and easy technique without complication and less expensive, could be performed as an outpatient procedure.
Radio frequency fistulotomy is a technique of performing simultaneous cutting and coagulation of the tissues, using a high frequency alternate current. Advantage of this technique is a nearly bloodless field, minimal postoperative pain and rapid healing
Advancement flap technique has become a popular technique to minimize the incidence of fecal incontinence. The main problem in flap surgery is shrinkage of the flap principally caused by inadequate blood supply, the reason for that might be inadequate dissection, dimension or tention at suture line.
Fibrin glue has the advantage of minimal risk to continence, but it offers a little benefit over other methods in terms of complex fistula healing. The precise role of fibrin glue in the treatment of anal fistula remains unclear due to lack of good quality clinical trials.
The newest modality of therapy for the treatment of fistula in-ano is the Surgisis AFP. The plug is cone shaped and made from porcine small intestinal submucosa. When placed in the fistula tract it is proposed to serve as a bioscaffold for native tissue regeneration and hence occlude the fistulous tract. Advantage of this technique is the simplicity and avoidance of sphincter injury. Limitation of its use is the relatively high cost of the plug and the lack of large scale controlled multi-center trials. Although the early has been positive. Prospective study by Johnson compared the anal plug to fibrin glue and concluded that anal plug is more effective for treating anorectal fistula.