Perianal abscess

What it is

Classification of anorectal abscesses goes by where the abscess sits against the internal and external sphincter and the levator ani muscle. The types are the perianal abscess, the ischioanal (ischiorectal) abscess, the intersphincteric or intramuscular abscess, and the supralevator abscess. The intersphincteric one is marked as the origin, and infection of the anal glands at the dentate line is where the whole thing starts.

How it presents

The usual story is a painful perianal swelling of a few days, with fever that comes and goes. The types do not look alike, and each picture belongs to one of them.

• Perianal abscess: superficial tender swelling.
• Ischiorectal abscess: deep, unable to see swelling, only tender and pain when sitting, so you will need US to localize it.
• Intersphincteric abscess: suggested when the patient feels the worst pain when he passes motion.
• Supralevator abscess: difficult to be diagnosed and usually associated with fever of unknown origin.