An Application of Super-pulsed TFL vs Ho:YAG Laser in Retrograde Intrarenal Surgery for Upper Ureter and Renal Stones: A Multi-center Prospective Randomized Controlled Trial

Endoscopic surgery is the predominant method for treating urinary tract stones. The field of surgery has progressed from traditional open procedures and percutaneous lithotripsy to more advanced techniques such as mini, micro, and ureteroscopy methods. RIRS, which stands for retrograde intrarenal surgery, is a therapeutic option for upper ureteric or renal stones that are less than 2cm. Although various energy systems have been employed for stone fragmentation during ureteroscopy, laser energy is the predominant method used for this purpose. Both domestic and foreign criteria recommend the holmium laser. The thermal effects of the Ho:YAG laser efficiently pulverise stones. As a result, it is currently the most widely used laser for conducting laser lithotripsy on stones in the urinary tract. Unfortunately, the holmium-YAG laser system has some intrinsic problems, such as different components having varying effects. 2. During the fragmentation process, the stone displacement is large and difficult to accurately control. 3. Some stones cannot be powdered, heat-damaged, or perforated. 4. Mucosal damage during fragmentation makes it easy to bleed and ooze. 5. The powdering efficiency is low, the fragmentation time is long, there is a lower energy conversion ratio, excessive heat generation in machines, noise, etc. Thus, clinical practice requires a new laser technology to overcome the holmium laser's limitations.

Thus, new laser systems are being created to fix the issue. The newest laser technology, super-pulsed thulium fiber laser (SPTFL), has promising results. A super-pulse fibre thulium laser is a pulsed fibre thulium laser that can be clinically used for lithotripsy. In 2005, in vitro experiments related to super-pulsed fibre thulium laser lithotripsy were first reported. Experimental data suggests that, compared with holmium laser, thulium laser has the following advantages in urinary tract stone lithotripsy: 1. TFL has higher lithotripsy efficiency, and the stone ablation speed is 1.5-4 times faster than that of Ho:YAG. 2. A safer lithotripsy with a 4-fold reduction in penetration depth and a limited temperature increase inside the cavity (up to 39 °C). 3. Lower costs: low maintenance costs, low fibre damage, low equipment volume (1/8), high energy conversion. Subsequently, an increasing number of in vitro experiments and clinical studies have been conducted internationally. However, there is a scarcity of studies in the literature that directly compare the effectiveness and stone free rates of the Holmium-YAG laser and SPTFL systems. Consequently, investigators are interested in conducting a formal multi-center prospective randomised clinical study to compare the two systems in RIRS.