In vitro fragmentation of gallstones: Comparison of electrohydraulic, electromagnetic and piezoelectric shockwave lithotripters

To compare the fragmentation efficiency of three different shockwave systems, 63 human gallstone triplets were disintegrated in vitro using an electrohydraulic (MPL 9000, Dornier), an electromagnetic (Lithostar Plus, Siemens) and a piezoelectric (Piezolith 2300, R. Wolf) lithotripter. Since each stone triplet was obtained from the same gallbladder, the concrements of one such set were identical in physicochemical parameters. According to the maximal diameter, the calculi were divided into group A (6 to 15 mm) and group B (16 to 30 mm). Shockwave application was terminated when residual fragments measured 4 mm or less. Forty-five triplets were fragmented at energy settings mainly used in clinical treatment of patients with gallbladder stones (MPL 9000: 20 kV; Lithostar Plus: setting 9 (maximal); Piezolith 2300: setting 3). The fragmentation endpoint was achieved in group A (n = 3 × 36) with the Piezolith 2300 after median 150 (range = 50 to 500) pulses and with the Lithostar Plus after 150 (50 to 750) pulses compared with 500 (50 to 1,500) pulses using the MPL 9000 (p < 0.01). In group B (n = 3 × 9) the Lithostar Plus (median = 750, range = 250 to 1,250 pulses) required fewer discharges than the Piezolith 2300 (1,250,250 to 2,500 pulses; p < 0.05) and the MPL (1,500,500 to 1,600 [upper limit] pulses; p < 0.01). At maximal intensities (MPL 9000: 26 kV; Lithostar Plus: setting 9; Piezolith 2300: setting 4), no statistically significant differences between the three tested shockwave systems were observed (Piezolith 2300: 100, 50 to 250 pulses; MPL 9000: 100, 50 to 500 pulses; Lithostar Plus: 100, 50 to 1000 pulses) for group A stones (n = 3 × 12) and group B stones (n = 3 × 6; Piezolith 2300 [500, 250 to 750 pulses], MPL 9000 [625,250 to 750 pulses] and Lithostar Plus [750, 250 to 1,000 pulses]). An adequate degree of fragmentation independent of the physical shockwave system can be achieved in vitro at maximal intensities for each tested stone size. At submaximal energy settings, better results were obtamed in stones up to 15 mm in diameter with the piezoelectric generator than with the electrohydraulic device, whereas in larger stones disintegration efficiency did not differ significantly between these two lithotripters. (HEPATOLOGY 1991;14:301–305.)