This research study is being conducted to assess the ability and efficiency of two laser systems to break up kidney stones during ureteroscopy with laser lithotripsy for kidney stone treatment.

Ureteroscopic stone treatment is a minimally invasive procedure commonly performed for kidney stones. Recently, the thulium fiber laser (TFL) has demonstrated effectiveness in this procedure. A new laser system developed by Dornier, the Thulio pulsed Thulium:YAG (p-Tm:YAG ) is beginning to be studied in vitro and in vivo. Dornier Thulio p-Tm:YAG may represent an attractive new laser platform, with comparable properties to TFL including decreased retropulsion, smaller dust, and improved ablation efficiency relative to Ho:YAG. Moreover, the p-Tm:YAG laser has been shown to be effective in treating a wide range of human stone types. The Dornier Thulio p-Tm:YAG laser has been tested clinically in a limited fashion via pilot studies in URS and the RevoLix Hybrid Thulium Laset (HTL) was studied in mini-PCNL. However, limited research has directly compared its efficacy and safety and no prospective comparative trials have been published.

This study aims to investigate whether Dornier Thulio p-Tm:YAG laser is non-inferior to TFL in terms of dusting ablation efficiency (J/mm3) and dusting ablation speed (mm3/s) for ureteroscopic stone treatment. To our knowledge no large-scale study has examined the outcomes of p-Tm:YAG compared to TFL for the treatment of kidney stones which warrants an investigation giving the promising results previously reported.

The primary objective is to assess stone dusting ablation efficiency (Joules/stone volume ablated) between both laser systems in vivo for ureteroscopic stone treatment . Secondary objectives include assessing stone dusting ablation speed (stone volume ablated/lasing time) and complication profile of both laser systems.

The investigators hypothesize that dusting ablation efficiency and speed of the p-Tm:YAG laser will be non-inferior to TFL for the treatment of renal stones totaling 7-20 mm in diameter with similar clinical and safety/complication outcomes.

Inclusion Criteria:

• Solitary renal stone 7 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 7-20 mm is required
• Must be a suitable operative candidate for flexible ureteroscopy per American Urological Association guidelines
• Must be able to give consent
• Bilateral ureteroscopy will be permitted but only the first side (per surgeon discretion) will be included in the study
• Surgeons participating in the study must be urological attending surgeons or fellows with subspecialty training in Endourology

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