Anal Fistula: Causes
What is an anal fistula?
Generally speaking, a fistula is a small tunnel or tract that connects one surface in the body to another. When such a tunnel occurs between the internal anal canal and the exterior skin of the body near the anus, it is called an anal fistula.
What causes an anal fistula?
An anal fistula is usually caused by an anal abscess, an infection-filled cavity occurring in the underlying tissues of the anal canal. When an abscess bursts or is opened, and the pus or fluid drains from it, an anal fistula is often formed. It then remains open, even after the abscess has healed.
If you have an inflammatory bowel disease (IBD)—such as diverticulitis, colitis, or Crohn’s disease—you are more likely to develop an anal abscess and fistula. Individuals with diseases that reduce the body’s immunity—such as AIDS or cancer—are also at a higher risk.
Does an abscess always result in a fistula?
Many anal abscesses do not result in anal fistulas. In fact, a fistula develops in only about half of all anal abscess cases.