Re: What causes an ischiorectal fistula?

An ischiorectal fistula is a communication from the rectum or sigmoid colon
through the fatty tissue in the ischiorectal fossa to the skin in the perianal 
area. That means that stool drains through this fistula to an open sore in 
the buttocks or next to the anus.

This can be caused by an abcess that developed in the rectum or lower 
colon. The abcess could be the result of an infected internal hemorrhoid
or rectal diverticulum. People with a disease called ulcerative colitis
may also develop fistulas. Any process that results in injury to the rectum
or lower colon can cause an abcess if it gets infected. When the abcess
disects through the fatty tissue to drain at the skin, a fistula is the result.