A fistula is an abnormal connection between two body surfaces. An anal fistula is an abnormal connection between
either the anal canal (the inside of the anus) or rectum, with the skin around the anus.
An anal fistula is an abnormal connection or tract between the anal canal (the inside of the anus) to the skin around the anus.
Anal fistula usually occurs as a result of a previous perianal abscess.
An anal fistula, almost always the result of a previous abscess, is a small tunnel connecting the anal gland from which the abscess arose to the skin of the buttocks outside the anus.
Some fistulas start as a small pimple around the anus. When it bursts, some pus and/or blood will be discharged out.
It then heals, but after a period of time, the pimple can form and burst again.
Another way that the fistula may manifest would be after an abscess has been drained. The wound heals nicely initially, but even after a long time, does not close completely. In some cases, the skin heals, but soon has a swelling under the scar, and then pus comes out when the point in the scar bursts.
Most of the time, a history of repeated swelling and discharge can point towards the diagnosis of the abscess, and
examination of the area may even reveal the presence of the tract that leads from the skin into the anus.
For some complex fistula, additional imaging such as endoanal ultrasound (by putting a small ultrasound probe into the anus) or magnetic resonance imaging (MRI) may be required to see the entire length of the fistula tract.