A very small tube or tract that leads from the anal canal
to the skin near the anal opening. Watery pus drains
through this opening and causes irritation to the skin.
Frequent signs and symptoms
Constant or intermittent discharge.
Firm-tender lump.
Pain during or after bowel movement.
Discoloration of skin surrounding fistula.
Causes
Erosion of tissue because of spreading abscess.
Extension from infection from a tear in the anal canal
lining.
May be found occasionally in association with trauma,
rectal infection (including chlamydia), carcinoma and
radiation therapy.
Risk increases with
Puncture wound in anal canal lining (e.g., from
eggshell or fishbone) or injury from an enema tip.