HOLMIUM-YAG LITHOTRIPSY YIELDS SMALLER FRAGMENTS THAN LITHOCLAST, PULSED DYE-LASER OR ELECTROHYDRAULIC LITHOTRIPSY

Purpose: The mechanism of lithotripsy differs among electrohydraulic L ithotripsy, mechanical lithotripsy, pulsed dye lasers and holmium:YAG lithotripsy. It is postulated that fragment size fl om each of these l ithotrites might also differ. This study tests the hypothesis that hol mium:YAG lithotripsy yields the smallest fragments among these lithotr ites. Materials and Methods: We tested 3F electrohydraulic lithotripsy , 2 mm. mechanical lithetripsy, 320 mu m. pulsed dye lasers and 365 mu m. holmium:YAG fiber on stones composed of calcium hydrogen phosphate dihydrate, calcium oxalate monohydrate, cystine, magnesium ammonium p hosphate and uric acid. Fragments were dessicated and sorted by size. Fragment size distribution was compared among lithotrites for each com position. Results: Holmium:YAG fragments were significantly smaller on average than fragments from the other lithotrites for all composition s. There were no holmium:YAG fragments greater than 4 mm., whereas the re were for the other lithotrites. Holmium:YAG had significantly great er weight of fragments less than 1 mm. compared to the other lithotrit es. Conclusions: Holmium:YAG yields smaller fragments compared to elec trohydraulic lithotripsy, mechanical lithotripsy or pulsed dye lasers. These findings imply that fragments from holmium:YAG lithotripsy are more likely to pass without problem compared to the other lithetrites. Furthermore, the significant difference in fragment size adds evidenc e that holmium:YAG lithotripsy involves vaporization.