Gas-containing gallstones: their influence on ultrasound images.

The ultrasound image of gas-containing gallstones was evaluated in three cases. In two, the stones were studied in vitro in a phantom gallbladder by ultrasound, and then by microradiographic techniques. The third case was investigated in vivo by ultrasound and computerized tomography (CT). The presence of gas-containing fissures, which are not detectable on ultrasound, was demonstrated. In contrast, wider fissures, or a true gas bubble, produce reverberation echoes which depend upon the quantity of gas present within the gallstone.