Perianal abscess - Located in the perianal space, superficially at the anal verge and continuous with the ischioanal fossa laterally.
Ischioanal abscess - Located in the ischioanal space with a superior boundary of the levator ani muscle, medial boundary of the external anal sphincter, and lateral boundary of the pelvic side wall.
Ischioanal abscesses may communicate bilaterally via the deep postanal space, resulting in a horseshoe abscess (need to divide anococcygeal ligament to open deep postanal space).
Intersphincteric abscess - Located in the intersphincteric plane between the internal and external anal sphincter muscles.
Supralevator abscess - Located in the extraperitoneal supralevator space, bounded medially by the rectum and laterally by the pelvic side wall.
During bedside drainage, local anesthetic should be injected into the skin surrounding the abscess before injecting into the point of maximal tenderness.
An incision is made in the perianal skin as close to the anal verge as possible to minimize the length of any associated fistula.
An incision is made over the area of maximal fluctuance, and skin edges are excised to prevent the tissue from reapproximating and prematurely sealing off the abscess cavity.
Educational aid only. Verify every dose, indication, and guideline against current institutional protocol. This is not a substitute for clinical judgment.
