[Experimental results and initial clinical experiences with the alexandrite laser lithotripter].

Although extracorporeal shock wave lithotripsy has become the standard therapy for urolithiasis, there are still indications for endoscopic stone treatment. Laser lithotripsy in association with flexible or semirigid "miniscopes" has become increasingly important for this form of therapy. So far the Nd: YAG and the pulsed dye laser have been used for laser lithotripsy in clinical applications. Since each system has its specific drawbacks, the new solid state alexandrite laser was developed to combine the advantages of the two existing systems. In order to evaluate the lithotriptic potential of the alexandrite laser, a stone model and eight human calculi were exposed to the laser in an experimental setting. Results with the stone model were comparable to those obtained with a reference Nd: YAG system. Adequate destruction was possible in all the human calculi except for one monohydrate stone. In the second part of the study, bladder and ureteric wall were exposed to the laser in ten female pigs, with different numbers of shock waves at various energy levels. While there was a relatively high incidence of early changes, late histological specimens 4-5 weeks after the exposure did not reveal any significant pathology. There was no stricture-formation in the ureter. Finally 12 patients were treated with ureteroscopical laser lithotripsy, and 8 of these were evaluatable. All were stone free without any additional lithotripsy and did not develop any secondary changes in the ureter. The alexandrite laser can therefore be expected to become a safe, reliable and cost-effective alternative for endoscopic stone treatment.