الفهرس 
Anatomy of Perianal RegionOnly 14 pages are availabe for public view
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Abstract
Perianal fistula is defined as a tract lined by granulation tissue which may have external opening, internal opening, or both external and internal openings.
They commonly occur in middle-aged men as a result of cryptoglandular infection, Crohn’s disease, radiotherapy, and secondary malignancy.
The most common presenting symptom is discharge (65% of cases), but local pain due to inflammation is also common.The treatment of fistulas requires surgery. While this is successful in most cases, it is associated with a significant prevalence of recurrence.
Perianal fistula may be high level, which opens at or above the level of anorectal ring, or lower level, which opens below the level of the anorectal ring.
The assessment of perianal fistula prior to surgery should include the state of internal and external openings, the fistula course, the side branches and the associated complications.
The most widely used classification of perianal fistula is Parks’ classification which includes intersphincteric, transsphincteric, extrasphincteric and suprasphincteric types.
The diagnosis of perianal fistula can be made out through examination under anesthesia, X ray fistulography, endoanal ultrasound and magnetic resonance imaging.
Endoanal ultrasound can be utilized to assess the sphincteric course of perianal fistula and to expect the site of internal opening, it is simply can’t evaluate the extrasphincteric course due to limited field of view. Other limitations include the operator dependence and absence of a coronal plane of imaging.
MRI is considered the method of choice in evaluation of perianal fistulae due to its ability to display the anatomy of the sphincter muscles with good contrast resolution in addition to its ability to evaluate the complex fistula tracks and to differentiate between pilonidal sinus tracts and perianal fistulas however, it is an expensive technique which can’t be used as a screening tool.