An anal fistula often follows drainage of an abscess and is an abnormal tube-like passageway from the anal canal to a hole in the skin near the anus’s opening. Body wastes traveling through the anal canal are diverted through this tiny channel and out through the skin, causing itching and irritation. Fistulas also cause drainage, pain, and bleeding. They rarely heal by themselves and usually need surgery to drain the abscess and “close off” the fistula.
Other perianal infections
Sometimes the skin glands near the anus become infected and need to be drained. Just behind the anus, abscesses can form that contains a small tuft of hair at the back of the pelvis (called a pilonidal cyst).
Sexually transmitted diseases that can affect the anus include anal warts, herpes, AIDS, chlamydia, and gonorrhea.