Introduction. The choice of an effective and safe method of disintegration of stones in upper and lower urinary tract is very important in the context of continuous scientific and technological progress. In current clinical urological practice, various lithotriptors with rigid and flexible probes are used for contact disintegration of stones, having both advantages and disadvantages. This study aimed to analyze the first results of the clinical application of the native Tm: fiber Urolaz laser (STA IRE-Polyus, Russia) for contact transurethral lithotripsy.
Materials and methods. The study comprised 56 patients who underwent transurethral contact thulium laser lithotripsy for 68 stones of the upper and lower urinary tracts between April and September 2017. Forty-four patients had kidney and ureteral stones, and twelve patients had urinary bladder stones. Twenty-four kidney stones were removed by retrograde intrarenal surgery using ureteral casing, flexible ureteropyeloscope and thulium laser, 32 stones in various ureteral segments – by rigid contact thulium laser ureterolithotripsy and 12 bladder stones – by thulium laser cystolithotripsy. The size of the upper urinary tract stones varied from 0.6 to 1.8 cm, bladder stones measured from 1.1 to 3.5 cm. Also, experimental studies were carried out to investigate the effects of the fiber thulium and holmium laser on the stone displacement and temperature environment during lithotripsy.
Results. Full stone fragmentation was achieved in 100% of patients. 47.7% of patients required additional lithoextraction of fragments; there was no retrograde migration of large stones. The mean duration of stone disintegration was 19 minutes. Postoperatively, 15.9% of patients had an exacerbation of pyelonephritis, which was successfully managed by conservative measures. The mean postoperative hospital stay was 2.4±1.1 days. At follow-up examination 4–6 weeks after surgery, one patient was found to have a residual symptomatic ureteral stone, which required extracorporeal short-wave lithotripsy. The experimental study showed that fiber thulium laser lithotripsy produced much less propulsion of artificial stone than Holmium laser lithotripsy. With the use of therapeutic power, neither of the lasers resulted in «dangerous» rises of the washing fluid temperature during stone disintegration.
Conclusion. Using the universal thulium laser system «Urolaz» provides a significant improvement in the effectiveness of endourologic upper urinary tract interventions and significantly reduces the likelihood of intraoperative trauma and postoperative complications, which contributes to improving the quality of specialized urological care.

Keywords: ureteropyeloscopy, thulium lithotripsy, laser, urolithiasis