Presentation
Perianal discharge and swelling and pain.
Patient Data
Long track extending from the skin of right anal margin, ascending in the medial right ischioanal fossa, penetrating the low right levator to enter the fat posterior to the anorectal junction, and then heading slightly inferiorly in the intersphincteric fat to an internal opening at the 6 o'clock position at the anorectal junction (i.e. a suprasphincteric anal fistula). There are no secondary tracks and no abscess. There is high T2 signal fluid within the lumen of the track, with a cuff of low signal fibrosis. No seton identified. Otherwise rectum and anal canal.
Case Discussion
As this track penetrates the low levator muscle, it is classified as a suprasphincteric track by the Parks classification, although if it penetrated the muscle just a couple of millimeters lower, it would be a high transsphincteric track, and in most instances, the differentiation between a high transsphincteric and suprasphincteric track is academic because the treatment would be the same.
Another distinction is between suprasphincteric and extrasphincteric tracks - the former typically penerate the levator muscle above the sphincters and then the track heads inferiorly to an internal opening at the anorectal junction or within the anal canal, whereas with the latter the internal opening is within the rectum.
The St James University Hospital classification for this particular track would be grade 5 (supralevator or translevator extension).