PARAMETERS INFLUENCING PIEZOELECTRIC SHOCK-WAVE LITHOTRIPSY OF BILIARY CALCULI

A total of 225 human gallbladder stones were. divided into sets of two , three, or four identical calculi (with maximum diameters of 6-26 mm) and submitted to piezoelectric shock wave lithotripsy in vitro in ord er to investigate the influence of the following parameters on stone d isintegration: shock wave intensity, pulse frequency, and various phys icochemical parameters such as the volume and viscosity of the fluid s urrounding the stone, the hardness of the calculus, and its chemical c omposition. The fragmentation efficacy increased with enhanced shock w ave energy (P < 0.01). If the volume of the fluid (30 mL) surrounding the calculus was small, the disintegration end-point (defined by maxim um fragment diameters less-than-or-equal-to 4 mm) was achieved after a lower number of pulses (median: 250 pulses) than in the case of a lar ge fluid volume (80 mL) (500 pulses; P < 0.01). On the other hand, how ever, factors such as the shock wave pulse rate (0.9 Hz vs 1.6 Hz), va riations in viscosity of a water-jelly mixture surrounding the stone, the chemical composition of the stones as determined by X-ray diffract ometry, and stone hardness were found to have no significant influence on the fragmentation efficacy.