Treatment Options
Coumarin-Dye Laser Lithotripsy

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.

Advantages

1. Laser is safe and effective
2. Laser does not damage the ureteral wall
3. Will not damage guide wires or baskets

Disadvantages

1. Difficulty in fragmenting calcium oxalate monohydrate stones
2. Cystine stones will not fragment
3. Less effective than Holmium laser
4. Requires eye protection
5. The machine requires turning on in advanced (20 minutes) of procedure
6. Maintenance is frequent and expensive
7. Initial capital costs are high

(click table to enlarge)

Suggested readings
Watson G, Murray S, Dretler S, et al: The pulsed dye laser for fragmentation of urinary calculi. J Urol 1987; 138:195.

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.