a fistula with its internal opening in the anal canal and its external opening in the skin near the anus
they originate from the anal glands which are located between the internal and external anal sphincter, and which drain into the anal canal
blockage of these glands can result in an perianal abscess which can extend to the anal skin and result in a fistula tract
if the fistula tract seals over, a further abscess may form
fistulae can be a cause of ano-rectal pain and can cause distress due to the chronic drainage of pus and the risk of recurrent abscess formation and a source for systemic haematogenous spread infections
most patients prefer to have elective surgical repair
begin at the rectum or sigmoid colon and proceed downward, through the levator ani muscle
Suprasphincteric fistulae
begin between the internal and external sphincter muscles, extend above and cross the puborectalis muscle, proceed downward between the puborectalis and levator ani muscles, and open an inch or more away from the anus
Transphincteric fistulae
begin between the internal and external sphincter muscles or behind the anus, cross the external sphincter muscle and open an inch or more away from the anus
Intersphincteric fistulae
begin between the internal and external sphincter muscles, pass through the internal sphincter muscle, and open very close to the anus
Submucosal fistulae
pass superficially beneath the submucosa and do not cross either sphincter muscle
