Ultrasonic detection of calcification in gallstones: "the reverberation shadow".

Observation of reverberations within a gallstone shadow (the "reverberation shadow") resulted in this study. Reverberation shadow was seen in sonograms of 27 patients with gallstones and three patients with milk of calcium bile. Calcification within gallstones was demonstrated by radiography or computed tomography in 22 of the 27 patients with gallstones, associated with the reverberation shadow. Whether the remaining five patients had calcified gallstones remains unknown. This study suggests that the reverberation shadow produced by gallstones indicates the presence of calcification within the gallstones.