Most anal fistula result from pyogenic anorectal abscesses  some are secondary to specific causes such as Crohn,s disease TB or carcinoma rarely they are secondary to actinmomycosis or lymphogranuloma venerum

Clinical features and diagnosis

anal diseases
anal fistula and abscesses
the most frequent symptoms are anal discharge pain and swelling .discharge tend to occur intermittently while swelling and pain are usually associated with abscess formation when the external opening is closed clinical examination may reveal the presence of one or more external openings discharge and soiling of underclothes .bidigital
examination placing the index finger inside the anal canal and the thumb on the outside may reveal the induration of the tract and occasionally the induration of the internal opening .Goodsall,s rule is useful in determining the possible location of the internal opening based on the location of the external opening although exceptions occasionally occur. Goodsall,s rule .when the external opening lies anterior to a transverse line between ischial tuberosities the internal opening tends to be located radially .conversely when the external opening lies posterior to this plane and those less than 3 cm from anal verge usually open internally in midline posteriorly. all patients must have rigid sigmoidoscopy to exclude inflammatory bowel disease and neoplasia  Radiological assessment is limited to selected cases if clinical assessment is difficult as in cases of complex or recurrent fistula MRI scan of the anal canal and perianal area can be invaluable in delineating the anatomy of these fistula final assessment is done intra operative by initial examination under anaesthesia using anoscopy to search for the internal opening as well as probing using mlleable probes injection techniques using methylene blue indigo carmine milk and hydrogen peroxide may also help to locate elusive tracts anal fistula have a primary tract but may also have an associated abscess cavity and or a secondary tract or tracts . some of these secondary tracts may be in the form of horseshoe extensions successful treatment depends on identification and dealing with all theses  tracts during surgery,

Classification and types anal fistula

have been traditionally classified according to the location of internal opening into low anal fistula (below puborectalis) or  high anal fistula (at or above puborectalis) and anorectum.SirAllanParks classified them according to the location of primary tract into 1- intersphincteric 2- transsphincteric 3- extrasphincteric 4- suprasphinteric

primary internal opening is on the dentate line runs through the internal sphincter and then between internal and external sphincters to open on the perineal skin . it may have a secondary high blind tract or rarely a second opening upward
higher than the dentate line

primary internal opening is on the dentate line runs through both the internal and external sphincters into the ischiorectal fossa and then to perineal skin it may have secondary tracks horizantally (horseshoe)or blind vertical secondary tracks infra- or supralevator

 primary internal opening is on the dentate line runs through the internal sphincter and then upwards intersphinterically and discharge through the levator ani into the ischiorectal fossa and then perineal skin .the tract curves above the puborectalis sling

the internal opening is above the levators and the track runs external to the external sphincter this type may be secondary to pelvic sepsis as diverticulitis and Grohn,s disease rectal trauma and rectal Grohn,s disease it may be secondary to development of a secondary supralevator tract in a transsphincteric fistula

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