We studied 25 patients with gangrenous cholecystitis and observed a new sonographic finding - striated thickening of the gallbladder wall - and three patterns of pericholecystic fluid collections. Heterogeneous thickening of the gallbladder wall was characterized by either multiple striations (alternating hypoechoic and hyperechoic layers) or irregular mass-like protrusions projecting into the gallbladder lumen. We observed striated thickening far more frequently (in 10 of 25 patients) than other findings reported previously as being associated with gangrenous cholecystitis, such as intraluminal membranes (1 in 25 patients) and mass-like protrusions into the gallbladder lumen (1 in 25 patients). Although the sensitivity and specificity of this finding cannot be determined by our study, we believe that mural striations in cases of acute cholecystitis should raise the question of gangrenous changes. Additionaly, we found that two subtypes of pericholecystic fluid collections (types II and III) were associated with gallbladder wall perforation and abscess formation more frequently than type I collections.