First clinical experiences with laser lithotripsy using the partially frequency-doubled double-pulse Neodym-YAG laser (FREDDY)

Purpose: The progressive improvement of flexible ureteroscopes in combinati on with laser lithotripsy allows performance of retrograde lithotripsy in t he entire urinary tract. The disadvantage of dye lasers are their extremely high cost, both in initial acquisition and maintenance, whereas holmium la sers involve the danger of ureteral perforation. We report our first clinic al experiences with the partially frequency-doubled double-pulse Neodym-YAG laser (FREDDY). The purpose of this study is to described the safe use of laser lithotripsy as an enhancement to the therapeutical spectrum for uroli thiasis in clinical practice. Materials and methods: In order to perform li thotripsy using a flexible ureterorenoscope, we introduced the partially fr equency-doubled double-pulse Neodym-YAG laser (Fa. CLYXON, Berlin, www.clyx on.com) in addition to the lithoclast. When partially doubling the frequenc y, a green light is emitted that ignites the plasma on the stone, which, in turn, completely absorbs the simultaneously emitted infrared light that "p umps" the plasma. This results in high disintegration efficiency without da maging soft tissue. 47 patients from an unselected group were investigated. Of the 47 stones, 1 4 (29.8 %) were located in the renal pelvis, 8 (17.0 %) in the upper third of the ureter, 5 (10.6 %) in the middle third of the ureter, 18 (38.3 %) in the lower third of the ureter, 2 (4.3 %) in the bladder. Analysis was perf ormed in respect to disintegration and primary stone-free rates. Three trea tments prematurely discontinued due to a defect of the URS were not include d in the evaluation. Results: Complete disintegration using the laser was achieved in 35 of 44 s tones (79.6 %). The reason for only partial fragmentation was difficult loc alization of the calculi in 3 stones and for six stones an insufficient dis integration capacity of the laser, especially for uric acid and cystine sto nes. In 4 treatments the lithoclast was used additionally. For stones in th e upper third of the ureter, complete disintegration was achieved in 6/7 (8 6 %) cases. in one case, fragments were washed up into the renal pelvis. 5/ 5 (100 %) stones in the middle third of the ureter and 16/17 (94 % ) stones in the lower third of the ureter were completely disintegrated. One cystin e stone showed no disintegration. Primary stone-free rates for ureteral cal culi located in the upper third of the ureter were 29 %, in the middle thir d of the ureter 20 % and 82 % in the distal third. There was no ureteral perforation in any of the cases. 13 of the analysed s tones were located in the renal pelvis. Complete disintegration was achieve d in 11/13 stones. Conclusion: Lithotripsy with the partially frequency-doubled double-pulse N eodym-YAG laser allows the user an easy and low-cost entry into laser litho tripsy. The insufficient disintegration of uric acid and cystine stones is outweighed by the safe laser application without danger of ureteral perfora tion. The relatively low primary stone-free rates - as reported in the pape r at hand - are due to the fact that, after complete disintegration, comple te extraction of the disintegrate is not mandatory. Besides conventional li thotripsy systems, laser lithotripsy via flexible URS will become a substan tial part of clinical practice.