The "coffee bean" sign in periappendiceal and peridiverticular abscess.

Four cases of right lower quadrant abscess, each a clinical diagnostic dilemma, were recognized as abscesses surrounding a perforated viscus by application of the "coffee bean" sign on sonographic examination. The appearance in the right lower quadrant of a brightly echogenic finger-like projection extending into a cystic mass, with or without scattered internal echoes, should suggest the possibility of periappendiceal or diverticular abscess.