Ureteroscopy and laser lithotripsy: technologic advancements

Innovations in Kidney Stone Removal

Urolithiasis is a common clinical condition, and surgical treatment is performed with different minimally invasive procedures, such as ureteroscopy, shockwave lithotripsy and percutaneous nephrolithotomy. Although the transition from open surgery to endourological procedures to treat this condition has been a paradigm shift, ongoing technological advancements have permitted further improvement of clinical outcomes with the development of modern equipment. Such innovations in kidney stone removal are new lasers, modern ureteroscopes, development of applications and training systems utilizing three-dimensional models, artificial intelligence and virtual reality, implementation of robotic systems, sheaths connected to vacuum devices and new types of lithotripters. Innovations in kidney stone removal have led to an exciting new era of endourological options for patients and clinicians alike.

Ureteroscopy and Shock Wave Lithotripsy Trends from 2012 to 2019 Within the US Medicare Dataset: Sharp Growth in Ureteroscopy Utilization

Introduction and Objective: Both ureteroscopy (URS) and shock wave lithotripsy (SWL) are cornerstones in the surgical management of urolithiasis in the United States. We hypothesized that URS utilization outpaced SWL utilization in recent years and quantified the magnitude of change over time for caseloads of URS and SWL among urologists from a national Medicare database. Methods: Using the public "Medicare Physician & Other Practitioners" database (https://data.cms.gov), we determined case numbers of SWL (current procedural terminology [CPT] 50590) and URS (CPT 52356 or 52353) from 2012 to 2019. In a subanalysis, we identified "high-volume stone urologists" as those in the upper quartile of case numbers for both SWL and URS in baseline years of either 2012 or 2013 and trended their caseload from 2012 to 2019. Linear estimation models assessed annual rates of change and their statistical significance. Results: In 2012, urologists performed 41,135 SWL procedures vs 21,184 URS. URS overtook SWL in 2017 and by 2019 was the dominant modality (60,063 URS vs 43,635 SWL). Between 2012 and 2019, total URS cases annually increased by 5700 (15%/year, p < 0.001), while the number of SWL cases peaked in 2015 and has since declined on average -1.6%/year (p = 0.020). The number of urologists performing URS steadily rose from 1147 in 2012 to 2809 in 2019, reflecting an additional 246 urologists (21%/year) performing URS annually. The caseload of high-volume stone urologists showed similar trends with average URS cases increasing by 2.9/year/urologist (9.8%/year, p < 0.001) and average SWL cases declining by 0.9/year/urologist (-1.7%/year, p = 0.023). Conclusions: URS utilization has increased dramatically and outpaced SWL utilization from 2012 to 2019 within the Medicare population. URS was increasingly used by both the general urologist population and high-volume stone urologists while SWL utilization has begun to decline.

Ureteral inflammatory edema grading clinical application

Purpose

To evaluate the relationship between endoscopic ureteral inflammatory edema (UIE) and ureteral lumen, formulate a preliminary grading method for the severity of UIE, and analyze the impact of different grades of UIE on endoscopic ureteral calculi surgery and prognosis.

Materials and methods

We retrospectively analyzed 185 patients who underwent ureteroscopic lithotripsy (URSL) for upper urinary tract stones between January 2021 and November 2021. The UIE grade and lumen conditions were assessed by endoscopic observation. The effect of UIE grade on URSL and on patient prognosis were analyzed by multiple linear regression and binary logistic regression.

Results

A total of 185 patients were included in the study. UIE grade showed a significant correlation with age, hydronephrosis grading (HG), ureteroscope placement time (UPT), surgery time (ST), hemoglobin disparity value (HDV), and postoperative ureteral stenosis (PUS) (P < 0.05). Logistics regression analysis showed a gradual increase in intraoperative UPT and ST with increase in UIE grade. The severity of UIE showed a negative correlation with improvement of postoperative hydronephrosis (IPH) and the appearance of PUS. HDV was significantly increased in patients with UIE grade 3.

Conclusions

UIE grading can be used as an adjunctive clinical guide for endoscopic treatment of upper urinary tract stones. The postoperative management measures proposed in this study can help inform treatment strategy for ureteral stones.

Image Distortion During Flexible Ureteroscopy: A Laboratory Model Comparing Super Pulsed Thulium Fiber Laser vs High-Power Ho:YAG Laser

Purpose: Digital ureteroscopes employ "chip-on-the-tip" technology that allows for significant improvement in image resolution. However, image distortion often occurs during laser lithotripsy owing to acoustic wave production. We sought to compare image distortion using different laser power settings and distances from the laser fiber tip to the scope for the Super Pulsed Thulium Fiber (SPTF) laser and high-power Holmium:YAG (Ho:YAG) laser. Materials and Methods: Ureteroscopy was simulated using a silicon kidney-ureter-bladder model fitted with a 12F/14F access sheath and the Lithovue™ (Boston Scientific), disposable digital flexible ureteroscope. At defined laser parameters (10, 20, 30 and 40 W, short pulse), a 200-μm laser fiber was slowly retracted toward the tip of the ureteroscope during laser activation. Image distortion was identified, and distance from the laser tip to the scope tip was determined. Data from the two lasers were compared utilizing t-tests. Results: After controlling for frequency, power, and laser mode, utilizing 1.0 J of energy was significantly associated with less feedback than 0.5 J (-0.091 mm, p ≤ 0.05). Increased power was associated with larger feedback distance (0.016 mm, p ≤ 0.05); however, increase in frequency did not have a significant effect (-0.001 mm, p = 0.39). The SPFT laser had significantly less feedback when compared with all Holmium laser modes. Conclusions: Increased total power results in image distortion occurring at greater distances from the tip of the ureteroscope during laser activation. Image distortion occurs further from the ureteroscope with Ho:YAG laser than with SPTF fibers at the same laser settings. In clinical practice, the tip of the laser fiber should be kept further away from the tip of the scope during ureteroscopy as the power increases as well as when utilizing the Ho:YAG system compared with the SPTF laser platform. The SPTF laser may have a better safety profile in terms of potential scope damage.

Advances in Ureteroscopy: New technologies and current innovations in the era of Tailored Endourological Stone Treatment (TEST)

Ureteroscopy has undergone many advances in recent decades. As a result, it is able to treat an increasing range of patient groups including special populations such as pregnancy, anomalous kidneys and extremes of age. Such advances include Holmium laser, high-power systems and pulse modulation. Thulium fibre laser is a more recent introduction to clinical practice. Ureteroscopes have also been improved alongside vision and optics. This article provides an up-to-date guide to these topics as well as disposable scopes, pressure control and developments in operating planning and patient aftercare. These advances allow for a custom strategy to be applied to the individual patient in what we describe using a new term: Tailored endourological stone treatment (TEST).

Level of evidence: 5

Simulation of Laser Lithotripsy-Induced Heating in the Urinary Tract

PURPOSE

Holmium laser lithotripsy is a common modality used to fragment urinary stones during ureteroscopy. Laser energy deposited during activation produces heat and potentially causes thermal bioeffects. We aimed to characterize laser-induced heating through a computational simulation.

MATERIALS AND METHODS

A finite-element model was developed and used to estimate temperature in the urinary tract. Axisymmetric models of laser lithotripsy in a renal calyx, the renal pelvis, and proximal ureter were created. Heat generation by laser and heat transfer were simulated under different laser powers between 5 and 40 W. Irrigation fluid flow was introduced at rates between 0 and 40 mL/min. The model was validated by comparison with previous in vitro temperature data in a test tube, then used to calculate heating and thermal dose in the three tissue models.

RESULTS

Simulated temperature rises agreed well with most in vitro experimental measurements. In tissue models, temperature rises depended strongly on laser power and irrigation rate, and to a lesser extent on location. Injurious temperatures were reached for 5-40 W laser power without irrigation, >10 W with 5 mL/min irrigation, 40 W with 15 mL/min irrigation, and were not found at 40 mL/min irrigation. Tissue injury volumes up to 2.3 cm³ were calculated from thermal dose.

CONCLUSIONS

The results suggest a numerical model can accurately simulate the thermal profile of laser lithotripsy. Laser heating is strongly dependent on parameters and may cause a substantial temperature rise in the fluid in the urinary tract and surrounding tissue under clinically relevant conditions.

Numerical Response Surfaces of Volume of Ablation and Retropulsion Amplitude by Settings of Ho:YAG Laser Lithotripter

Objectives

Although laser lithotripsy is now the preferred treatment option for urolithiasis due to shorter operation time and a better stone-free rate, the optimal laser settings for URS (ureteroscopic lithotripsy) for less operation time remain unclear. The aim of this study was to look for quantitative responses of calculus ablation and retropulsion by performing operator-independent experiments to determine the best fit versus the pulse energy, pulse width, and the number of pulses.

Methods

A lab-built Ho:YAG laser was used as the laser pulse source, with a pulse energy from 0.2 J up to 3.0 J and a pulse width of 150 μs up to 1000 μs. The retropulsion was monitored using a high-speed camera, and the laser-induced craters were evaluated with a 3-D digital microscope. The best fit to the experimental data is done by a design of experiment software.

Results

The numerical formulas for the response surfaces of ablation speed and retropulsion amplitude are generated.

Conclusions

The longer the pulse, the less the ablation or retropulsion, while the longer pulse makes the ablation decrease faster than the retropulsion. The best quadratic fit of the response surface for the volume of ablation varied nonlinearly with pulse duration and pulse number.

Digital ureteroscopes: technology update

The field of ureteroscopy has undergone a continual evolution since the first ureteroscopes were introduced. Over the past 10 years, we have entered into the digital era of ureteroscopy with both semirigid and flexible options becoming available. The following review looks at the benefits and drawbacks of digital flexible ureteroscopes as well as the current commercially available options.

Flexible ureteroscopy: Technological advancements, current indications and outcomes in the treatment of urolithiasis

The last 3 decades have witnessed great improvements in the technology and clinical applications of many minimally invasive procedures in the urological field. Flexible ureteroscopy (fURS) has advanced considerably to become a widely utilized diagnostic and therapeutic tool for multiple upper urinary tract pathologies. The most common indication for fURS is the treatment of upper urinary tract stones with the aid of Holmium:Yttrium Aluminium Garnet (YAG) laser lithotripsy. Advancements in endoscope technologies and operative techniques have lead to a broader application of fURS in the management of urolithiasis to include larger and more complex stones. fURS has proved to be an effective and safe procedure with few contraindications. Continued progression in fURS may increase its clinical applicability and supplant other procedures as the first line treatment option for urolithiasis.