In vitro comparison of shock wave lithotripsy machines

Purpose: We tested the hypothesis that shock wave lithotripsy machines vary in the ability to fragment stones to small size. Materials and Methods: Calcium oxalate monohydrate, calcium hydrogen phosph ate dihydrate, cystine and magnesium ammonium phosphate hexahydrate calculi were fragmented in vitro with the 22 kV. Dornier HM3, 20 kV. Storz Modulit h SLX,\\, 15.6 kV. Siemens Lithostar C, 24 kV. Medstone STS-T,** 26 kV. Hea lthTronics LithoTron 160,dagger dagger 20 kV. Dornier Doli and 22.5 kV. Med ispec Econolith double dagger double dagger lithotriptors. Stones were give n 500 or 2,000 shocks, or the Food and. Drug Administration limit. Post-lit hotripsy fragment size was characterized using sequential sieves and compar ed. Results: Stone mass was statistically similar in the cohorts (p >0.94). Fra gment size decreased as the number of shocks increased when the machine and stone composition were constant. Magnesium ammonium phosphate hexahydrate calculi were completely fragmented by all devices. At Food and Drug Adminis tration treatment limits the mean incidence per device of calcium hydrogen phosphate dihydrate, calcium oxalate monohydrate, cystine and magnesium amm onium phosphate hexahydrate stones rendered into fragments greater than 2 m m. was 0% for the HM3, Modulith SLX and Lithostar C, 10% for the STS-T, 3% for the LithoTron 160, 29% for the Doll and 18% for the Econolith (p = 0.04 ); 0% for the HM3, Modulith SLX, Lithostar C, STS-T and LithoTron 160, 4% f or the Doll and 9% for the Econolith (p = 0.15); 1% for the HM3, 0% for the Modulith SLX, 1% for the Lithostar C, 10% for the STS-T, 14% for the Litho Tron 160, 3% for the Doll and 9% for the Econolith (p = 0.44); and 1% for t he HM3, 0% for the Modulith SLX, 1% for the Lithostar C, 10% for the STS-T, 14% for the LithoTron 160, 3% for the Doll and 9% for the Econolith (p = 0 .44), respectively. Conclusions: Shock wave lithotriptors vary in fragmentation ability. The HM 3, Modulith SLX and Lithostar C machines yield smaller fragments than other machines.