A perianal abscess (also calle anorectal abscess) is a collection of pus outside the anus. It arises from an infection at one of the anal crypts of Morgani which leads to inflamation and abscess formation. Most cases of perianal abscesses are sporadic, though there are certain situations which elevate the risk for developing the disease, such as diabetes mellitus, crohn's disease, chronic steroid treatment and others. Ischiorectal, inter and intrasphincteric abscesses have been described.