Laser lithotripsy: a review of 20 years of research and clinical applications.

Four new technologies have transformed the treatment of urinary calculi: electrohydraulic lithotripsy, ultrasonic lithotripsy, extracorporeal shock wave lithotripsy, and laser lithotripsy. Initial attempts to ablate urinary calculi by continuous wave CO2, ruby, and Nd-YAG lasers failed because of excess thermal injury and inability to pass the laser energy via a flexible fiber. Basic laboratory studies then demonstrated that short pulsed laser energy absorbed by the calculus resulted in fragmentation. The parameters that produced optimal urinary calculus fragmentation were found using the flashlamp pumped tunable dye laser, with the following parameters: wavelength: 504 nm; pulse duration: 1 microsec; fiber: 250 micro silica-coated quartz; repetition: 5-20 Hz. Use of pulsed dye laser caused no tissue damage. The mechanism of fragmentation is light absorption, plasma development, and repetitive acoustic shock wave action with resultant fragmentation. The techniques for application of laser to calculi have been successful, and new, miniature instruments have been developed. Laser lithotripsy is a successful method for fragmenting ureteral calculi. The small caliber of the laser fiber makes this method useful for treating calculi in narrow, tortuous ureters; impacted calculi; distal calculi in ureters that cannot be dilated, via the percutaneous route for stones in calyces or impacted in the upper ureter. Investigations are continuing to optimize fragmentation of harder calculi and to use laser fragmentation within the kidney. Laser lithotripsy may also be used to fragment biliary calculi.