The pulse-dye laser is safe and effective in the treatment of impacted ureteral stones. However, this laser is relatively ineffective against cystine calculi. Moreover, the fragments produced by Ho: YAG lasers are smaller than those produced by pulsed dye lasers. The differences between the Pulse-dye laser and the Ho:YAG laser are summarized in Table below.
Coumarin dye (wavelength of 504 microns) laser lithotripsy is a flash-lamp pump laser using coumarin green dye as a laser medium. At this wavelength, this laser will have the maximum effect on the stone and a minimal effect of the ureteral wall. When the stone absorbs the laser light, a smaller amount of heat is generated which creates a cavitation bubble. The expansion and contraction of this bubble creates acoustic waves, which pass into the stone resulting in fragmentation.
Segura JW: Pulsed dye laser for treatment of ureteral calculi. Urol Clin N Am 1988; 15(2): 257-262.
Grasso M, Bagley DH: Endoscopic pulsed dye laser lithotripsy: 159 consecutive cases. J Endo 1994; 8:25-27.