Causes of anorectal abscesses and fistulas
A cryptoglandular origin seems to provide the best explanation. Four to 10 anal glands enter the anal canal at the level of the crypts in the dentate line. The glands extend back into the internal sphincter two thirds of the time and into the intersphincteric space half the time. Blockage of the gland leads to an overgrowth of bacteria with resultant pressure necrosis and abscess formation. An abscess or infection that causes an abnormal communication between two surfaces (such as the anal canal and perianal skin) creates a fistula.
Types and locations of anorectal abscesses
Types and locations are submucosal, intersphincteric, perianal (anal verge), ischiorectal (perirectal), and supralevator.
What is the best treatment for an anorectal abscess?
Prompt incision and drainage. There is little or no role for antibiotics (exceptions are immunocompromised patients and patients with prosthetic heart valves or severe cellulitis) and no reason to wait for the abscess to point or become fluctuant before surgical treatment.