The pulsed dye laser, emitting at wavelengths of 504 nm. for 1 microsecond. at a frequency of 5 Hz. transmitted via a 250 mu in diameter silicon-coated quartz fiber, was passed into the ureter through the working channel of a 9.5F rigid ureteroscope. Seventeen patients with ureteral calculi too large to be extracted directly, who were unable to be treated by extracorporeal shock wave lithotripsy or who otherwise would have required transureteral or percutaneous ultrasonic stone removal, underwent attempted stone fragmentation by pulsed dye laser application. Of the 17 calculi 16 were fragmented to spontaneously passable or easily extractable fragments. There was no significant ureteral injury, thermal or otherwise, attributable to laser energy action. At 3-month followup 15 of the 17 ureters had improved and 2 showed evidence of ureterscopic injury. The mechanism of stone fragmentation by laser is small volume "shock wave" formation.

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