Fragmentation of biliary calculi by means of extracorporeally generated piezoelectric shock waves

A new extracorporeal piezoelectric lithotripter was tested for its gallstone disintegration capability. A total of 177 surgically removed gallbladder stones were submitted to piezoelectric shock-wave treatment. Prior to shock-wave application, the diameter, weight, and volume of all the stones and CT density and MR signal intensity of selected stones were determined. After shock-wave application, the chemical composition of the stones was investigated by x-ray diffractometry and/or infrared spectrometry. All the stones (maximum diameter 6-30 mm) were successfully fragmented; calculi with a maximum diameter of 17 mm, a maximum weight of 1800 mg, and a maximum volume of 2 cc were regularly disintegrated into fragments less than or equal to 4 mm. The number of shock waves required correlated most closely with volume (r = 0.82, P less than 0.001), weight (r = 0.81, P less than 0.001) and, to a somewhat lesser degree, diameter (r = 0.62, P less than 0.001). No correlation was found between the chemical composition, CT density, or MR intensity of the calculi and the number of pulses needed for fragmentation.