Flexible ureteroscopy is characterized as first-line therapy for the treatment of renal stones < 2 cm in size. This involves passing a flexible endoscope into the renal pelvis through the urethra, bladder and ureter in a retrograde fashion. Holmium: YAG laser remains the preferred energy modality to subsequently break stones of this size into fragments small enough to remove or pass spontaneously through the ureter. Advances in the understanding of laser energy delivery have led to the recent commercialization of the "Moses Effect" - the creation of vapor bubbles/cavities between the laser fiber tip and the target through which laser energy can more efficiently travel. Lumenis was the first to optimize this laser phenomenon and market it as "Moses Technology" in their Lumenis Pulse P120H laser system. This system is already FDA approved through the 510K pathway and is commercially available. The purpose of this study is to evaluate the potential of Moses laser technology to reduce operative time compared to non-Moses settings for ureteroscopic treatment of nephrolithiasis.

There is ongoing debate on the optimal means of laser stone fragmentation, and Moses technology is the latest advancement to raise questions regarding clinical utility. Initial preclinical studies demonstrated significantly reduced stone retropulsion and higher stone ablation volume with Moses technology, leading to the conclusion that the system allows more efficient laser lithotripsy. Human studies also showed that laser lithotripsy with Moses technology utilized laser energy in less time for stone fragmentation: 10.0 (2.6-15.0) min without vs 6.0 (2.8-13.0) min with Moses technology.

Others have evaluated the cost effectiveness of Moses technology in their own cohort of 40 patients who underwent standard laser lithotripsy by comparing a 35% projected decrease in procedure time against the cost of the Moses laser fiber and machine. Mean stone size was 10.2 mm in this group of patients, and mean lasing time was 3.0 minutes. While a significant positive association was seen between stone size and laser time, cost analysis failed to show a benefit in using Moses technology across sizes.

To date, there are limited clinical data obtained through rigorous study methodology. In addition, knowledge gaps remain regarding the effect of Moses technology on other clinically meaningful outcomes such as stone-free rate. Therefore, the investigators propose a multi-center, prospective, randomized, double blind clinical trial to further assess the effect of Moses technology for lithotripsy. The investigators aim to study a broader range of outcomes which will be facilitated by being the largest study to date. The investigators also aim to study novel outcomes such as grading retropulsion and visibility by independent blinded review as well as effects of Moses technology on independently reducing surgeon burnout. Indeed, a randomized, double blind clinical trial evaluating Moses technology in 66 patients undergoing ureteroscopy was presented as a 2018 European Association of Urology abstract. While this single center study demonstrated safety and reduced fragmentation time as well as procedure time using Moses technology, it did not show a significant difference in stone-free rates. This study is also yet to be published as a manuscript.

Inclusion Criteria:

• Solitary renal stone 8 to 20 mm in size or in the case of multiple stones the conglomerate diameter (additive maximal diameter of all stones on axial imaging of computed tomography) of 8-20 mm is required
• Must be a suitable operative candidate for flexible ureteroscopy per urologic guidelines
• Must be 18 years or older
• Must be able to give consent

Exclusion Criteria:

• Concomitant stones in the ureter
• Prior ipsilateral upper urinary tract reconstructive procedures or history of ipsilateral ureteral stricture
• Prior radiotherapy to the abdomen or pelvis
• Neurogenic bladder or spinal cord injury
• Pregnancy
• Untreated UTI