Advances in Lasers for the Treatment of Stones-a Systematic Review

Ureteroscopy and Laser Lithotripsy for Large (≥2 cm) Upper Tract Urinary Stones in Pediatric Patients: Outcomes from a Pediatric Endourology Referral Center

Introduction: The global prevalence of pediatric urolithiasis is increasing. Managing large urinary stones in pediatric populations poses a particular clinical challenge. This study evaluates the safety and efficacy of ureteroscopy and laser stone fragmentation (URSL) for treating large upper urinary tract stones in pediatric patients. Methods: A retrospective analysis of the prospective database was conducted on pediatric patients who underwent URSL for stones ≥2 cm between 2011 and 2023 (14 years) at the University Hospital Southampton, UK. Patient demographics, stone characteristics, operative details, stone-free rates (SFR), and complications were analyzed. Results: In total, 23 patients (median age 11 years) underwent URSL. The mean total stone length was 24.7 ± 6.49 mm, with 12 (52.2%) having multiple stones. Prestenting, ureteral access sheath, and postop stenting were used in 9 (39.1%), 4 (17.4%), and 10 patients (43.5%), respectively. Holmium laser was used, and the SFR after the first procedure was 91.3%, with no procedural complications. There was only one complication (postoperative fever, Clavien-Dindo I) reported. The median length of stay was 1 day. Conclusion: URSL is safe and efficient for treating large upper tract urinary stones in pediatric patients, demonstrating high SFR and low complication rate. This could offer an alternative treatment modality to percutaneous surgery in large upper urinary tract stones, although parents need to be adequately counseled about it.

Evaluation of pulse modulation settings for optimal pop-dusting efficiency using the Quanta Litho 150 laser: An in vitro study

Purpose

The novel Quanta Litho 150 W (Samarate, Italy) was recently introduced and incorporates new pulsed modulation settings. We sought to analyze ablation rate and efficiency in short pulse (SP), virtual basket (VB), and vapor tunnel (VT) pulsed modulations, in an in vitro pop-dusting simulation across different settings at a fixed power of 30 Watts (W) and fixed periods of time.

Materials and Methods

Seven millimeter BegoStone phantoms were subjected to lithotripsy in a simulated calyx using Holmium: yttrium:aluminum garnet Quanta System 150 W. 30 W was applied at different settings across three pulse modulation modes: SP, VB, and VT. Ablation rate and efficiency were and compared between the three groups.

Results

Maximum ablation efficiency for the VB and VT groups was achieved at VB 2J x 15 Hz and VT at 2.5 J x 12 Hz. Ablation efficiency decreased with higher Joules. VB at 1.5 J x 20 Hz and SP at 2.5 J x 12 Hz were the only settings to obtain 85% ablation at 5 min.

Conclusions

In vitro laser lithotripsy using a BegoStone phantom, VB at 2J x15 Hz and VT at 2.5 J x 12 Hz were the most efficient setting for pop-dusting with the Quanta Litho 150. The highest efficiency (mg/min) was achieved with VB at 2 J x 15 Hz and VT at 2.5 J x 12 Hz at 1:15 min.

New Techniques and Technologies in Flexible Ureteroscopy

This article provides a step-by-step guide to flexible ureteroscopy (URS), with focus on some of the newer techniques and technologies available to facilitate treatment of complex stones. In it we review indications, preoperative evaluation, surgical steps, postoperative care, troubleshooting methods, and complication management. Furthermore, we will explore advances in laser technologies, the integration of suction mechanisms, and the incorporation of intrarenal pressure measurement systems in flexible URS.

Emerging Role of Laser Lithotripsy for Bladder Stones: Real-World Outcomes from Two European Endourology Centers with a Systematic Review of Literature

Introduction and Objective: We aimed to look at the evidence for laser lithotripsy for bladder stones (BSs) to provide results from two centers on bladder calculi treatment. In addition, the outcomes of prostatic and other surgical interventions performed in nearly half of all patients. Methods: A retrospective analysis of two large European endourology tertiary centers for patients who underwent laser lithotripsy for BS between 2016 and 2024 (7 years). All patients provided consent and were counseled for the study accordingly, and the studies were registered as an audit in the individual centers. Results: A total of 122 patients were analyzed (mean age of 68.17 ±16.38 years; male:female ratio of 97:25). Thirteen (10.7%) patients had a preoperative long-term catheter. Overall, 42 (34.43%) patients had multiple stones (n = 2.19, ±2.08), with a median stone burden of 32.36 ± 24.13 mm. The mean operative time was 61.6 ± 37.25 minutes, with an overall stone-free rate (SFR) of 95.1% (n = 116). Postoperative complications were noted in nine (7.38%) patients, which included urinary tract infection or sepsis (n = 4, 3%), pain (n = 2, 1.6%), and bleeding/acute urinary retention/urethral stone (n = 1 each, 0.82%). All the complications were Clavien-Dindo I/II and treated conservatively. Six patients (4.9%) with planned concomitant surgical intervention needed a completion (second) intervention at a later date. Sixty patients (49.2%) had concomitant procedure along with their BS treatment. Twenty-two patients (18%) with a mean prostate size of 60.71 cc (±30.50 cc) underwent a transurethral resection of prostate (n = 16, 13.1%) or bladder neck incision (n = 6, 4.9%). Others underwent ureteroscopy (n = 13, 10.7%), transurethral resection of bladder tumor (n = 5, 4.1%), suprapubic catheter repositioning (n = 10, 8.2%), or urethral dilation (n = 10, 8.2%). The mean hospital stay was 1.4 ± 1.33 days. Conclusion: Laser fragmentation of BSs stands out as a safe and efficient choice with a good SFR and low risk of major complications, and perhaps should be considered the new gold standard for BS management. It also allows for concomitant treatment of enlarged prostate and other endourologic procedures with good outcomes.

Efficacy and safety of thulium fiber laser versus holmium: yttrium-aluminum-garnet laser in lithotripsy for urolithiasis: a systematic review and meta-analysis

This meta-analysis compares the efficacy and safety of thulium fiber laser (TFL) with holmium: yttrium-aluminum-garnet (Ho: YAG) laser in lithotripsy for urolithiasis. A literature search was conducted across PubMed, Embase, Web of Science, the Cochrane Central Register of Controlled Trials (CENTRAL), and ClinicalTrials.gov to identify studies published up to July 2024. Studies evaluating clinical outcomes for urolithiasis treated with either Ho: YAG laser or TFL were included. The meta-analysis, using RevMan 5.4 software, focused on comparing the stone-free rate (SFR) between the two lasers. A total of 21 studies were included. TFL was associated with a significantly higher SFR (RR 1.09, 95% CI: 1.02 to 1.16; P = 0.01), shorter operation time (SMD - 1.24, 95% CI: -1.82 to -0.66; P < 0.001), shorter lasing time (SMD - 1.26, 95% CI: -1.98 to -0.54; P < 0.001), shorter hospital stay (SMD - 2.08, 95% CI: -4.15 to -0.02; P = 0.05), reduced stone basket usage (SMD 0.50, 95% CI: 0.33 to 0.76; P = 0.001), and a lower total number of intraoperative complications (RR 0.67, 95% CI: 0.47 to 0.96; P = 0.03). However, TFL was also associated with a higher risk of postoperative sepsis (RR 5.32, 95% CI: 1.71 to 16.56; P = 0.004). Subgroup analyses revealed that TFL achieved a higher SFR in several subgroups, including ureteral stones, non-MOSES technology, and follow-up periods of ≥ 3 months, among others. In conclusion, TFL lithotripsy shows superior efficiency and safety compared to the Ho: YAG laser, though the increased risk of postoperative sepsis warrants further investigation.

Renal pelvis pressure and flowrate with a multi-channel ureteroscope: invoking the concept of outflow resistance

Understanding renal pelvis pressure (PRP) during ureteroscopy (URS) has become increasingly important. High irrigation rates, desirable to maintain visualization and limit thermal dose, can increase PRP. Use of a multi-channel ureteroscope (m-ureteroscope) with a dedicated drainage channel is one strategy that may facilitate simultaneous low PRP and high flowrate. We sought to define the relationship between PRP and flowrate across a range of different outflow resistance scenarios with an m-ureteroscope versus a single-channel ureteroscope (s-ureteroscope). The m- or s-ureteroscope was placed into the pelvis of a validated silicone kidney-ureter model. Trials were conducted at irrigation pressures (50-150 cmH20) and five different outflow resistance scenarios simulated with catheters of different lengths and diameters. PRP was measured with a fiber optic pressure sensor positioned in the renal pelvis. Flowrate was determined by measuring the mass of drainage fluid over 60 s. PRP was lower with the m-ureteroscope than the s-ureteroscope when equivalent flowrates were delivered (i.e. 34 vs. 82 cmH20 respectively with 15 ml/min irrigation in a high outflow resistance scenario). Flowrate was higher with the m-ureteroscope than the s-ureteroscope when equivalent irrigation pressures were applied (i.e. 28 vs. 14 ml/min respectively with irrigation pressure 150 cmH20 in a high outflow resistance scenario). The m-ureteroscope has improved pressure-flow dynamics imparting important clinical benefits. More importantly, this approach to framing ureteroscopy in the context of pressure-flow relationships related by resistance values allows quantification of ureteroscopy within a deterministic system, which can be used to streamline future device development and technological innovation.

Vapor Channel Oscillations in Laser Lithotripsy

OBJECTIVES

Laser-based endoscopic procedures present special challenges to deliver energy for ablation or coagulation of target tissues. When optical fiber-target quasi-contact (< 0.5 mm distance) cannot be maintained or is undesirable, the creation of intervening vapor bubbles and channels provide for the necessary transmission of laser energy to the target. This work investigates the characteristics and the dynamics of vapor channels that directly affect ablation efficiency and ablation rate and are known to effect stone movement, all of which impact procedure efficiency and safety.

METHODS

A simplified, experimental model for thulium fiber laser (1940 nm) lithotripsy consists of a water-filled cuvette and a vertically oriented laser fiber (200 μm core diameter) with its tip at 9 mm for "quasi-free" bubble generation and at vapor channel working distances 1-5 mm from and centered on the transparent cuvette bottom simulating a target's surface. Laser power transmission is recorded and synchronized with video frames from a high-speed camera (24,260 frames per second) to capture the induced vapor channels' and bubbles' development.

RESULTS

Laser-induced channel transmission from 0% to 100% for 1, 2, and 3 mm fiber-target distances undergoes oscillations with average periods of 0.32, 0.64, and 1.0 ms, respectively, for 500 W laser output power. For fixed fiber-target distances of 0.5, 1, and 2 mm, the variation of these average oscillation frequencies across laser powers from 500 to 1000 W is much smaller, not exceeding 14%. For fiber-target distances in the range of 1-5 mm, the fraction of the 500 W laser's total pulse energy delivered to the target for 1, 2, and 3 ms pulses linearly decreases from 0.78 to less than 0.2. The channel and bubble dynamics begin with a spherical seed bubble expansion centered on the distal fiber tip that evolves into a pear shape whose surface exhibits periodic irregularities attributable to laser beam interruption by water droplets within the developing bubble.

CONCLUSIONS

The study of laser-induced channel oscillations provides quantitative information relating fiber-target distance to channel oscillation frequency and energy transmission onto a target. These oscillations directly effect ablation efficiency and ablation rates that are important parameters for the optimization of a procedure's safety and duration. Insights that may lead to further reduction in retropulsion are also presented. Lasers Surg. Med. 00:00-00, 2024. © 2024 Wiley Periodicals LLC.

A review of the Moses effect and its applications in endourology

The holmium:yttrium aluminum garnet laser, the gold standard for lithotripsy, is widely used in various endourological fields. Their physical characteristics contribute to the Moses effect. This narrative review aimed to analyze the current knowledge of the Moses effect and its applications in endourology. The Moses effect involves the rapid formation of a vapor bubble that allows the remaining energy to reach the target with less attenuation. Lumenis® developed pulse modulation technology, the MOSES™ technology, that harnesses the Moses effect to optimize holmium energy. Preclinical studies concluded that the new technology improves stone retropulsion, allowing for reduced lithotripsy duration. However, the heterogeneity of clinical studies and the lack of randomized controlled trials do not allow definitive conclusions. The MOSES™ technology has also been applied in holmium laser enucleation of the prostate, reducing enucleation and hemostasis times, leading to improved enucleation efficiency. However, minimal changes occurred in hemoglobin or hematocrit levels and no significant differences were noted in complications or functional outcomes. Further research is needed to fully evaluate the benefits and limitations of MOSES™ technology in clinical practice.

Safety and efficacy of laser lithotripsy for treatment of bladder calculi: evidence from a systematic literature review

PURPOSE OF REVIEW

Bladder stones account for 5% of all urinary tract calculi. Contributing factors include bladder outflow obstruction, infections, foreign bodies, or neurogenic voiding dysfunction. This necessitates an effective treatment modality, and with advances in medical technology, minimally invasive techniques using lasers are being widely adopted. This systematic review aims to assess the efficacy and safety of laser lithotripsy for treating bladder stones.

RECENT FINDINGS

A thorough literature review (PROSPERO: CRD 42024551910) was conducted using appropriate search terms up to March 2024. Only original studies written in English, with at least 10 patients with bladder stones treated with laser, were considered with inclusion. A total of 8 studies (411 patients) were identified on screening with a mean age of 59.6 ± 8.5 years and a male: female ratio of 326 : 14. These reviews covered a geographical area of Asia, Europe, and the USA. The mean stone size was 3.7 ± 0.7 cm, and an overall stone-free rate (SFR) postlaser lithotripsy was 96%. Mean operation time was calculated to be 76.36 ± 47.10 min and an overall complication rate of 16.5% (n = 68), with the most common being haematuria (n = 22), followed by UTI (n = 18), incontinence (n = 8), urosepsis (n = 6), clot retention (n = 4), mucosal injury (n = 3) and urinary retention (n = 3). All complications were minor and there were no Clavien >II complications.

SUMMARY

Laser lithotripsy for bladder stone achieves an excellent success rate in the form of SFR, combined with a low risk of major complications, and allows concomitant treatment of enlarged prostate, and should be considered in all patients.

Development of a Bladder Injury Classification System for Endoscopic Procedures: A Mixed-methods Study Involving Expert Consensus and Validation

BACKGROUND AND OBJECTIVE

The widespread adoption and rapid integration of new technologies and techniques in endoscopic and laser bladder interventions, particularly endoscopic enucleation, have led to new types of bladder injuries. This underscores the need for an intraoperative injury classification system. This study aims to develop and validate the Bladder Injury Classification System for Endoscopic Procedures (BICEP), which standardizes the classification of complications and intervention requirements.

METHODS

This mixed-methods study involved experts from the European Association of Urology Section of Urotechnology to standardize and validate the BICEP classification system. An iterative process involving focus groups, expert surveys, and revisions assessed clarity, relevance, comprehensiveness, and practicality. Validity was confirmed through expert surveys conducted in two rounds for face and content validity, using a 5-point Likert scale to correlate ratings with expected outcomes.

KEY FINDINGS AND LIMITATIONS

The novel BICEP classification system categorizes bladder injuries into ten subcategories with scores ranging from 0 to 4, reflecting injury severity and management requirements. Face validity was demonstrated by a 95% consensus on the system's clarity, relevance, and comprehensiveness. Content validity was supported by high acceptance rates in expert surveys, with average scores of 4.53 and 4.58 in the first and second rounds, respectively. This demonstrates strong support for its applicability in clinical practice. However, the primary limitation is the lack of external validation.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Our study demonstrates that the BICEP system is a robust and comprehensive classification system, with strong support for its face and content validity. The BICEP system is a proposal based on expert opinion, and additional studies are necessary to ensure its widespread adoption and efficacy.

PATIENT SUMMARY

Our study addressed the critical need for standardized classification in the increasingly widespread context of urology endoscopic technologies by focusing on intraoperative evaluation, reporting, and standardization of bladder injuries. This study provides a globally standardized basis for the classification and treatment of bladder injuries in urology endoscopic procedures.

Comparing thulium fiber versus high power holmium laser in bilateral same sitting retrograde intrarenal surgery for kidney stones: Results from a multicenter study

PURPOSE

Traditionally, bilateral urolithiasis treatment involved staged interventions due to safety concerns. Recent studies have shown that same-sitting bilateral retrograde intrarenal surgery (SSB-RIRS) is effective, with acceptable complication rates. However, there's no clear data on the optimum laser for the procedure. This study aimed to assess outcomes of SSB-RIRS comparing thulium fiber laser (TFL) and high-power holmium:yttrium-aluminum-garnet (Ho:YAG) laser in a multicenter real-world practice.

MATERIALS AND METHODS

Retrospective analysis was conducted on patients undergoing SSB-RIRS from January 2015 to June 2022 across 21 centers worldwide. Three months perioperative and postoperative outcomes were recorded, focusing on complications and stone-free rates (SFR).

RESULTS

A total of 733 patients were included, with 415 in group 1 (Ho:YAG) and 318 in group 2 (TFL). Both groups have similar demographic and stone characteristics. Group 1 had more incidence of symptomatic pain or hematuria (26.5% vs. 10.4%). Operation and lasing times were comparable. The use of baskets was higher in group 1 (47.2% vs. 18.9%, p<0.001). Postoperative complications and length of hospital stay were similar. Group 2 had a higher overall SFR. Multivariate regression analysis indicated that age, presence of stone at the lower pole, and stone diameter were associated with lower odds of being stone-free bilaterally, while TFL was associated with higher odds.

CONCLUSIONS

Our study shows that urologists use both lasers equally for SSB-RIRS. Reintervention rates are low, safety profiles are comparable, and single-stage bilateral SFR may be better in certain cases. Bilateral lower pole and large-volume stones have higher chances of residual fragments.

Exploring the Impact of Gender-Specific Approaches inRetrograde Intrarenal Surgery: Effects on Operative Efficiency and Patient Recovery

Objective

Very limited data are available exploring the potential influence of gender on Retrograde Intrarenal Surgery outcomes. This study investigates the gender-specific influence of ShuoTongureteroscopy (ST-urs) and Flexible Ureteroscopy (F-urs) surgeries on operation efficacy and patient recovery in a sample of the Somali population.

Materials and Methods

We enrolled 390 participants. Participants were stratified into four gender-specific subgroups based on ureteroscopy operation type: 27.7% males in S-urs (group1), 44.4% females in S-urs (group2), 18.7% males in F-urs (group3), and 9.2% females in F-urs (group4). Primary outcomes included operation time, postoperative hospital stay duration, and VAS Pain Score. Multivariate logistic regression was used to assess associations.

Results

The mean age was 29.53 ± 7.61 years, 72.1% male and 27.9% female, with 46.4% of the patients undergoing ST-urs and 53.6% undergoing F-urs. Women had higher odds of prolonged hospital stays (OR = 2.62, 95% CI: 1.43-4.82, p < 0.001) and post-operation pain (OR = 5.06, 95% CI: 2.95-8.68, p = 0.002). Among men who underwent F-urs procedure, there was a significantly higher odds ratio (OR) of 6.14 (95% CI: 2.86-13.19, p < 0.001) for experiencing a long operation time. Conversely, for females, those who underwent S-urs surgery had a notably lower OR of 0.32 (95% CI: 0.13-0.79, p = 0.013) for long operation time, whereas those who underwent F-urs surgery exhibited a substantially elevated OR of 5.36 (95% CI: 1.85-15.53, p < 0.001). Both females undergoing F-urs surgery (OR: 5.16, 95% CI: 2.61-10.21, p < 0.001) and those undergoing F-urs surgery (OR: 5.25, 95% CI: 2.17-12.73, p < 0.001) experienced significantly higher post-operative pain.

Conclusion

Our research reveals gender disparities in retrograde intrarenal surgery outcomes. Women experience longer hospital stays and higher postoperative pain levels compared to men. F-urs procedures are associated with longer operation times and hospital stays, particularly affecting women. Contrarily, ST-urs offers shorter operation times for women but leads to prolonged hospital stays and heightened postoperative pain.

Turning up the HEAT Surgical simulation of the Moses 2.0 laser in an anatomic model

INTRODUCTION

With advancements in laser technology, urologists have been able to treat urinary calculi more efficiently by increasing the energy delivered to the stone. With increases in power used, there is an increase in temperatures generated during laser lithotripsy. The aim of this study was to evaluate the thermal dose and temperatures generated with four laser settings at a standardized power in a high-fidelity, anatomic model.

METHODS

Using high-fidelity, 3D-printed hydrogel models of a pelvicalyceal collecting system with a synthetic BegoStone implanted in the renal pelvis, surgical simulation of ureteroscopic laser lithotripsy was performed with the Moses 2.0 holmium laser. At a standard power (40 W) and irrigation pressure (100 cm H2O), we evaluated operator duty cycle (ODC) variations with different time-on intervals at four different laser settings. Temperature was measured at two separate locations: at the stone and ureteropelvic junction.

RESULTS

Greater cumulative thermal doses and maximal temperatures were achieved with greater ODCs and longer laser activation periods. There were statistically significant differences between the thermal doses and temperature profiles of the laser settings evaluated. Temperatures were greater closer to the tip of the laser fiber.

CONCLUSIONS

Laser energy and frequency play an important role in the thermal loads delivered during laser lithotripsy. Urologists must perform laser lithotripsy cautiously when aggressively treating large renal pelvis stones, as dangerous temperatures can be reached. To reduce the risk of causing thermal tissue injury, urologists should consider reducing their ODC and laser-on time.

Global Trends in Kidney Stone Awareness: A Time Series Analysis from 2004-2023

BACKGROUND

Despite the prevalence and incidence of kidney stones progressively increasing worldwide, public awareness of this condition remains unclear. Understanding trends of awareness can assist healthcare professionals and policymakers in planning and implementing targeted health interventions. This study investigated online search interest in "kidney stone" by analyzing Google Trends, focusing on stationarity of the trends and predicting future trends.

METHODS

We performed time series analysis on worldwide Google monthly search data from January 2004 to November 2023. The Augmented Dickey-Fuller (ADF) test was used to assess the stationarity of the data, with a p-value below 0.05 indicating stationarity. Time series forecasting was performed using the autoregressive integrated moving average to predict future trends.

RESULTS

The highest search interest for "kidney stone" (score 100) was in August 2022, while the lowest was in December 2007 (score 36). As of November 2023, search interest remained high, at 92. The ADF test was significant (p = 0.023), confirming data stationarity. The time series forecasting projected continued high public interest, likely reflecting ongoing concern and awareness. Notably, diverse regions such as Iran, the Philippines, Ecuador, the United States, and Nepal showed significant interest, suggesting widespread awareness of nephrolithiasis.

CONCLUSION

This study highlighted that "kidney stone" is a consistently relevant health issue globally. The increase and stationarity of search trends, the forecasted sustained interest, and diverse regional interest emphasize the need for collaborative research and educational initiatives. This study's analysis serves as a valuable tool for shaping future healthcare policies and research directions in addressing nephrolithiasis related health challenges.

Safety and Efficacy of "Dusting and Pop-Dusting" with High-Power Laser for Treatment of Large Pediatric Stones with Ureteroscopy and Lasertripsy: Prospective Outcomes from a University Teaching Hospital

Introduction: The wide use of high-power laser has changed the landscape of ureteroscopy and lasertripsy (URSL). We wanted to look at the role and outcomes of high-power holmium:yttrium-aluminum-garnet laser for URSL in pediatric stone disease. Methods: A prospective analysis of consecutive pediatric patients treated with "Dusting and Pop-dusting" using a high-power laser was done between January 2016 and March 2022. The project was registered with our audit committee. Data were analyzed for patient demographics, stone characteristics, operative details, procedural outcomes, and complications. Stone-free rate (SFR) was defined as fragments ≤2 mm on postoperative ultrasound imaging 2-3 months after the procedure. Results: A total of 35 patients underwent 43 procedures (1.2 procedure/patient) during the study period with a mean age of 9.4 years (range 1-16 years) and a male:female ratio of 13:22. The stone location was in the kidney in 32 (91.4%) patients of which 8 were in multiple renal locations. The mean stone size was 18 mm (range 10-39 mm), with the pre- and post-stent rates of 37% and 56%, respectively. An access sheath was used in 19 (44%) procedures. The overall SFR on ultrasound scan was 94% (n = 33) with no procedural complications noted in our series and a mean length of stay of 0.9 days. Conclusion: Pediatric URSL using a high-power laser achieves a high SFR even for large and multiple renal stones with no complications noted in our prospective series. Parents must, however, be counseled about the need for staged procedures, which might be needed for large stones.

Analyzing global research trends and focal points in the utilization of laser techniques for the treatment of urolithiasis from 1978 to 2022: visualization and bibliometric analysis

Laser lithotripsy is gaining global prominence and is a dynamically progressing field marked by a continual influx of new and comprehensive research each year. Recently, there has been a noticeable shift toward the adoption of various kinds of lasers, such as holmium: yttrium-aluminum-garnet (Ho:YAG) and thulium fiber (TFL) lasers. Consequently, we aim to conduct a bibliometric analysis to analyze key areas of research activity within scientific publications that center on the utilization of laser techniques in urolithiasis. A search of the literature spanning from 1978 to 2022 was carried out on 25 December 2023 using the Scopus database to explore research related to the application of laser techniques for urolithiasis treatment. Visualization analysis was performed using VOSviewer software (version 1.6.20). We examined 962 publications that met the specified criteria, 791 (82.22%) of which were original articles. The analysis of the retrieved publications indicated a consistent increase in research output from 1978 to 2022; a particularly noteworthy surge occurred after 2003. In particular, the U.S. claimed the leading position as the most productive country, contributing 211 articles (21.93%). However, India had the highest research productivity according to the adjustment index of 19.08. In the European region, 324 publications (33.68% of the total) originated from 25 countries. The Journal of Endourology contributed the most between 1978 and 2022 (n = 96, 9.98%). The most cited paper examined the effectiveness of holmium: yttrium-aluminum-garnet (Ho:YAG) lasers, while a subsequent study focused on the use of a thulium fiber laser (TFL), an emerging laser technology that has gained increased recognition. Co-occurrence analysis revealed three distinct clusters focusing on the types of laser technology, minimally invasive approaches, and success rate/postoperative complications. This comprehensive investigation delves into the global landscape of laser use for the treatment of urolithiasis. This review supports the emerging clinical concept of using various types of laser technology for urolithiasis treatment. Moreover, the hot issues that researchers should focus on based on the findings of this study are the use of different types of laser lithotripsy in view of the surgical approach, success rate and complications.

Comparison of high and low pulse energy dusting protocols using holmium: YAG laser in flexible ureteroscopy for treatment of renal stones

Objectives

The management of renal stones, particularly those less than 2 cm in diameter, has changed with the development of endourological techniques, among which flexible ureteroscopy (FURS) using laser for lithotripsy has become a cornerstone. This study aims to compare the effectiveness of high pulse energy versus low pulse energy laser settings in renal stone dusting by Holmium YAG laser.

Patients and Methods

This prospective randomized study was conducted between September 2021 and November 2023 to compare the efficacy and safety of high energy versus low-energy pulse settings using a Holmium: YAG laser dusting of renal stones less than 2 cm in diameter. A total of 174 adult patients were included, divided equally into high- and low-pulse energy groups, based on the energy settings of the laser high energy (ranged from 1.2-2.5 Joules and frequency of 8 hz) and low energy (less than 0.5 Joules and frequency ≥ 15 hz) using the dusting ‎technique with non-touch non-stop approach. The study sought to evaluate the impact of these settings on stone fragmentation efficiency, operative time, laser energy consumption, and postoperative outcomes, including stone-free rates and complications.

Results

The study involved 174 patients who underwent renal stone lithotripsy and showed that using high pulse energy laser dusting settings significantly reduced operative times and more rapid dusting compared to low pulse energy settings, without affecting the stone-free rate. The study observed no significant differences in stone size or location between both groups. Minor postoperative complications were similar between both groups, indicating high pulse energy settings for lithotripsy dusting.

Conclusion

The efficacy of high pulse energy dusting in enhancing stone removal during surgery, potentially reducing operative time. Further validation through larger-scale studies is needed to solidify these findings. This technique presents a promising solution, particularly in regions with limited resources where acquiring expensive laser equipment is challenging.

Holmium:YAG laser-assisted intraductal sialendoscopic lithotripsy under local anesthesia

OBJECTIVES

This retrospective multi-institutional chart review study aims to present results from patients treated with Holmium:YAG laser-assisted sialendoscopic intraductal lithotripsy under local anesthesia.

METHODS

Preoperative ultrasound and/or CT were used for location and measurement of the stones. Local anesthesia was applied in all patients, Marchal all-in- one 1.3 mm and Erlangen 1.6 sialendoscopes were used. The laser was used with power settings limited by discomfort or pain. Inclusion criteria were stone size (all >5 mm) and fixed stones.

RESULTS

42 patients, 48 stones were treated (30 males/12 females), 21 submandibular and 21 parotid. Ages ranged from 20 to 70 years (95 % CI: 43.37-51.58). Mean size was 6.2 mm (95 % CI: 5.71-6.72). Complete fragmentation was achieved in 66.7 % and incomplete in 33.3 %. Out of the incomplete fragmented 14 cases, seven (50 %) remained symptom free on follow-up. Maximum duration was 120 min. Minimum power settings of the laser was 4.8 Watts and maximum 18 Watts. Six patients expressed pain or discomfort that limited power increase and duration of the procedure. Total follow up time was 10 years. There were no major complications such as hemorrhage, nerve paresis or skin ulceration.

CONCLUSION

The procedure is safe under local anesthesia, well tolerated by most patients and should be used in cases of small fixed and "intermediate-sized" stones as a single modality. Discomfort may limit power settings and duration. The later is the major disadvantage of the method.

WATTS happening? Evaluation of thermal dose during holmium laser lithotripsy in a high-fidelity anatomic model

PURPOSE

To evaluate the thermal profiles of the holmium laser at different laser parameters at different locations in an in vitro anatomic pelvicalyceal collecting system (PCS) model. Laser lithotripsy is the cornerstone of treatment for urolithiasis. With the prevalence of high-powered lasers, stone ablation efficiency has become more pronounced. Patient safety remains paramount during surgery. It is well recognized that the heat generated from laser lithotripsy has the potential to cause thermal tissue damage.

METHODS

Utilizing high-fidelity, 3D printed hydrogel models of a PCS with a synthetic BegoStone implanted in the renal pelvis, laser lithotripsy was performed with the Moses 2.0 holmium laser. At a standard power (40 W) and irrigation pressure (100 cm H2O), we evaluated operator duty cycle (ODC) variations with different time-on intervals at four different laser settings. Temperature was measured at two separate locations-at the stone and away from the stone.

RESULTS

Temperatures were highest closest to the laser tip with a decrease away from the laser. Fluid temperatures increased with longer laser-on times and higher ODCs. Thermal doses were greater with increased ODCs and the threshold for thermal injury was reached for ODCs of 75% and 100%.

CONCLUSION

Temperature generation and thermal dose delivered are greatest closer to the tip of the laser fiber and are not dependent on power alone. Significant temperature differences were noted between four laser settings at a standardized power (40 W). Temperatures can be influenced by a variety of factors, such as laser-on time, operator duty cycle, and location in the PCS.

Should endoscopic laser excision be offered as the first-line management for patients with eroded mesh? Outcomes of a systematic review of literature

PURPOSE OF REVIEW

Mesh erosions following previous synthetic sling/mesh surgery for stress urinary incontinence (SUI) have become increasingly common. This systematic review provides evidence for the role of laser excision as a first-line management in patients with eroded mesh.

RECENT FINDINGS

Fourteen articles (173 patients) were included for the final review. Among these, 138 patients (79.8%) were submitted to trans-urethral laser excision of eroded urethral/bladder mesh over a median time to presentation of 36.6 months. Over a median follow-up of 23.6 months, 88 (63.7%) reported a complete resolution, 32 (23.2%) reported persistence or recurrence of SUI and 17 (12.3%) presented with recurrent mesh erosion. The success rate after a single endoscopic procedure was 66.5, vs. 93.5% after additional endoscopic procedures, with only 9 (6.6%) requiring open surgical excision. Overall, there were seven (5.1%) postoperative complications including two urethrovaginal fistulas, two UTIs and haematuria each, and one case of urethral diverticulum.

SUMMARY

Laser excision of eroded mid-urethral slings into either the bladder or urethra is a challenging complication of minimally invasive incontinence surgery. Laser excision was able to achieve a good success rate with single or staged endoscopic procedure with a low risk of complication. It represents a valid first treatment option, although patients should be managed in mesh referral centres in collaboration with uro-gynaecology teams.

Comparison of Thulium Fiber Laser versus Holmium laser in ureteroscopic lithotripsy: a Meta-analysis and systematic review

OBJECTIVES

To compare the efficacy and safety of thulium fiber laser (TFL) to holmium: YAG (Ho: YAG) laser in ureteroscopic lithotripsy for urolithiasis.

METHODS

PubMed, Web of Science, Embase, CENTRAL, SinoMed, CNKI database, VIP and Wanfang Database were systematically searched for all relevant clinical trials until September 2023. References were explored to identify the relevant articles. Meta-analysis was carried out for the retrieved studies using RevMan5.4.1 software, and the risk ratio, mean difference and 95% confidence interval were expressed. Statistical significance was set at p < 0.05. The main outcomes of this meta-analysis were stone-free rate (SFR), perioperative outcomes and intraoperative or postoperative complications.

RESULTS

Thirteen studies, including 1394 patients, were included. According to the results of pooled analysis, TFL was associated with significantly higher stone-free rate (SFR) [0.52, 95% CI (0.32, 0.85), P = 0.009], shorter operation time [-5.47, 95% CI (-8.86, -2.08), P = 0.002], and less stone migration [0.17, 95% CI (0.06, 0.50), P = 0.001]. However, there was no significant difference in terms of the laser time, duration of hospital stay, drop of hemoglobin level, total energy, postoperative ureteral stenting, the incidence of intraoperative complications or postoperative complications between TFL and Ho: YAGs.

CONCLUSION

The findings of this study demonstrated several advantages of TFL in terms of higher SFR, shorter operative time and less stone migration.

TRIAL REGISTRATION

The protocol of this systematic review was listed in PROSPERO ( www.crd.york.ac.uk/PROSPERO ) (Protocol number: CRD42022362550).

Radiological Density, Atomic Numbers, and Stone Fragmentation of Bego Stones Used for Research in Endourology: Comparison to Real Urinary Stones

Objective: The aim of the study was to characterize artificial stones used for research in endourology in terms of radiological properties and hardness, based on stone fragmentation, and to compare them with real stones. Materials and Methods: We built artificial stones using BegoStone Plus™ powder (BEGO, Lincoln, RI), with powder (g)-water (mL) ratios ranging from 15:03 to 15:12. The CT Gemstone Spectral Imaging Software® (GE Medical Systems, LLC, Waukesha, WI) was used to evaluate the radiological density in HU and spectral properties. Stone fragmentation was assessed in an in vitro experimental setting. These properties of artificial stones were compared with real urinary calculi. Results: Regarding radiological density in terms of HUs, 15:03 artificial calculi showed similar results when compared with real stones comprising calcium oxalate and calcium phosphate. The 15:03 and 15:04 artificial stones showed similar spectral property results to calcium pyrophosphate stones. The 15:11 artificial stones showed similar stone fragmentation results to real stones comprising uric acid, and 15:03 artificial calculi showed similar results to apatite and cystine stones. Conclusions: Artificial stones are useful for research in endourology. Stones with a powder (g)-water (mL) ratio of 15:03 proved to mimic real hard stones in terms of HUs, atomic number, and stone fragmentation in our study and could be used as artificial hard stones, and 15:11 stones showed similar stone fragmentation to uric acid stones. Our study might suggest that standard Bego stones are useful to investigate different areas in endourology, but not radiological properties because radiological homogeneity is not ensured unless more sophisticated mixing methods are used.

The optimal Holmium laser settings for disintegration of cystine and calcium oxalate monohydrate stones: In vitro study

Objective

Disintegrating cystine and calcium oxalate monohydrate stones present a formidable challenge owing to their hardness and distinct composition. This study aimed to establish optimal laser settings for these hard stones lithotripsy.

Patients and Methods

Cystine and calcium oxalate monohydrate stones were extracted from two patients. Two experiments were conducted in vitro by utilizing a 272 μm laser fiber with variable settings to disintegrate the cystine and calcium oxalate monohydrate stones. In the first experiment, energy was adjustable while frequency was constant, whereas the second experiment involved constant energy with adjustable frequency on each type of stone and each experiment was repeated three times to ensure robustness and reliability.

Results

Our findings indicated that for cystine stones, use of higher total power with high energy and low frequency proved to be effective. Conversely, for calcium oxalate monohydrate stones, settings involving higher total power with low energy and high frequency demonstrated superior efficacy and safety.

Conclusion

Holmium (Ho: YAG) laser settings with higher total power, high energy, and low frequency effectively disintegrate cystine stones despite increased heat, which was measured by a thermometer with a thermocouple. For calcium oxalate monohydrate stones, higher total power, high frequency, and low energy settings are recommended and safe.

Assessment of stone ablation rate using the Moses technology modes with different energy and pulse settings: An experimental study

Objectives

To compare lithotripsy ablation rate with the Moses modes versus conventional pulse modes when using the Holmium:Yttrium-Aluminum-Garnet (Ho:YAG) laser.

Methods

The Lumenis® Pulse P120H Holmium Laser System and a 365 μm Moses D/F/L fiber were used to assess stone ablation rate in conventional Short and Long Pulse as well as Moses Contact and Distance at 10 W (0.5Jx20Hz and 2Jx5Hz) and 60 W (1Jx60Hz and 2Jx30Hz). Hard and soft phantom stones were formed, and all tests were conducted in a custom experimental configuration installed in a saline-filled bath. The laser was delivered up to 3 kJ of total energy. The fragmentation pattern was assessed via photographs in each cohort.

Results

The time to reach the target energy was 5 min and 50 s in all 10 W and 60 W trials, respectively. In both stone types, ablation was more effective when high-power, high-energy and Moses Distance was utilized. In soft stones, the lowest ablation rate was detected in the Long Pulse modality in all power, energy and frequency settings. Overall, when dusting settings (high-frequency, low-energy) were used, a deeper single cavitation was observed rather than small cavitations.

Conclusions

The most effective pulse modality as evaluated via stone ablation rate depends on the stone hardness as well as energy and frequency settings. In both hard and soft stones, ablation is more effective when 60 W (2Jx30Hz) power settings and Moses Distance are used. Tailored laser settings in terms of energy and frequency could be set for each case scenario.

Comparison of ureteoroscopy and laser stone fragmentation between Holmium: YAG laser with MOSES versus non-MOSES technology: a prospective single-center propensity score-matched analysis using similar laser settings

Background

In vitro studies have shown that the holmium Modulated Optics Enhancement Systems (MOSES) technology can lead to an increase in the efficacy of lithotripsy and a reduction of retropulsion, but clinical evidence comparing it to non-MOSES technology is still scarce. We did a comparison of ureteoroscopy and laser stone fragmentation (URSL) between Holmium:YAG laser with MOSES versus non-MOSES technologies.

Methods

Patient data and outcomes were prospectively collected and analyzed regarding patient demographics, stone parameters, and clinical outcomes. Patients undergoing URSL with standard holmium laser without MOSES technology (Group 1) were compared to holmium laser with MOSES (Group 2) using the same clinical laser settings (0.4-1 J, 20-40 Hz) with dusting and pop-dusting technique. The independent t-test, Mann-Whitney U test, and Chi-squared test were used, with a p-value of < 0.05 as significant. Given the different sizes of the cohorts, we performed a propensity score 1:1 matched analysis.

Results

A total of 206 patients (1:1 matched) with a male:female ratio of 94:112 and a median age of 56 (range: 39-68) years were analyzed. Groups 1 and 2 were matched for ureteric stones (27.7% and 22.3%, p = 0.42), pre-stenting (37% and 35%, p = 0.66), the mean number of stones (1.76 ± 1.3) and (1.82 ± 1.4, p = 0.73), and ureteral access sheath use (37% and 35%, p = 0.77) respectively.While there was no significant statistical difference in clinical outcomes, the stone size was slightly larger in Group 2, 14.8 ± 10.8 mm vs 11.7 ± 8.0 mm, for a lower operative time 42.7 ± 30.6 min versus 48.5 ± 25 min, lower perioperative complication rates 3.9% versus 4.9% and a higher stone-free rate 90.3% versus 87.4%.

Conclusion

While the use of MOSES technology was slightly beneficial for the treatment of stones in terms of clinical outcomes, this was not statistically significant. As this debate continues, there is a need for high-quality randomized studies to show if there is a true difference in these outcomes.

Advances in lasers for the minimally invasive treatment of upper and lower urinary tract conditions: a systematic review

PURPOSE

Technological advancements in laser lithotripsy are expanding into numerous fields of urology, like ureteroscopy (URS), percutaneous nephrolithotomy (PCNL), and benign and malignant soft-tissue treatments. Since the amount of research regarding lasers in urology has grown exponentially, we present a systematic review of the most recent and relevant advances encompassing all lasers used in urological endoscopic treatment.

METHODS

We performed a literature search using PubMed (May 2023) to obtain information about lasers for urological purposes. We included only recent data from published articles between 2021 and 2023 or articles ahead of print.

RESULTS

Lasers are widely used in lithotripsy for ureteric, renal, and bladder stones, benign prostate surgery, and bladder and upper tract tumor ablation. While the holmium (Ho:YAG) laser is still predominant, there seems to be more emphasis on pulse modulation and newer lasers such as thulium fiber laser (TFL) and pulsed Tm:YAG laser.

CONCLUSION

The use of lasers and related technological innovations have shown increasing versatility, and over time have proven to be invaluable in the management of stone lithotripsy, treatment of benign and malignant prostate diseases, and urothelial tumors. Laser endoscopic treatment is heavily based on technological nuances, and it is essential to know at least the basics of these technologies. Ultimately the choice of laser used depends on its availability, cost, surgeon experience and expertise.

Initial experience with the graphical user interface for laser parameters setting of a new thulium fibre laser source device for urinary pathologies treatment

BACKGROUND AND OBJECTIVE

We aimed to evaluate the concordance between the pre-settings ranges of thulium fibre laser (TFL) (Coloplast TFL Drive, Denmark) with easy-to-use graphical user interface and the laser settings used by a high-volume endo-urologist during surgical procedures.

MATERIALS AND METHODS

In October 2022, we prospectively collected data of 67 patients who underwent TFL Drive (Coloplast, Denmark) for the management of urinary stones. Urothelial tumour (upper tract urinary cancer (UTUC) and bladder) 200 and 150 μm laser fibres were used for procedures. Stones characteristics (size and density) tumours and stenosis localizations, laser-on time (LOT), and laser settings were recorded. We also assessed the ablation speed (mm3/s), laser power (W), and Joules/mm3 values for each lithotripsy.

RESULTS

A total 67 patients took part in the study. Median age was 52 (15-81) years. 55 (82%), 8 (12%), and 4 (6%) patients presented urinary stones, urothelial tumour, and stenosis, respectively. Median stone volume was 438 (36-6027) mm3 and median density was 988 (376-2000) HU. Median pulse energy was 0.6 (0.3-1.2), 0.8 (0.5-1) and 1 J for urinary stones, urothelial tumour and stenosis respectably. Endoscopically stone-free rate was 89%. Graphical user interface and surgeon accordance with the safety range were observed in 93.2%, 100% and 100% for urinary stones, UTUC and stenosis, respectively.

CONCLUSION

During endoscopic procedures for urinary stones treatment, it is frequently needed to change laser parameters. These new TFL and GUI technology parameters remained in the pre-set security range in 94.1% of procedures.

What to expect from the novel pulsed thulium:YAG laser? A systematic review of endourological applications

INTRODUCTION

Several preclinical studies about a novel pulsed-thulium:yttrium-aluminum-garnet (p-Tm:YAG) device have been published, demonstrating its possible clinical relevance.

METHODS

We systematically reviewed the reality and expectations for this new p-Tm:YAG technology. A PubMed, Scopus and Embase search were performed. All relevant studies and data identified in the bibliographic search were selected, categorized, and summarized.

RESULTS

Tm:YAG is a solid state diode-pumped laser that emits at a wavelength of 2013 nm, in the infrared spectrum. Despite being close to the Ho:YAG emission wavelength (2120 nm), Tm:YAG is much closer to the water absorption peak and has higher absorption coefficient in liquid water. At present, there very few evaluations of the commercially available p-Tm:YAG devices. There is a lack of information on how the technical aspects, functionality and pulse mechanism can be maximized for clinical utility. Available preclinical studies suggest that p-Tm:YAG laser may potentially increase the ablated stone weight as compared to Ho:YAG under specific condition and similar laser parameters, showing lower retropulsion as well. Regarding laser safety, a preclinical study observed similar absolute temperature and cumulative equivalent minutes at 43° C as compared to Ho:YAG. Finally, laser-associated soft-tissue damage was assessed at histological level, showing similar extent of alterations due to coagulation and necrosis when compared with the other clinically relevant lasers.

CONCLUSIONS

The p-Tm:YAG appears to be a potential alternative to the Ho:YAG and TFL according to these preliminary laboratory data. Due to its novelty, further studies are needed to broaden our understanding of its functioning and clinical applicability.

Thermal Safety Boundaries for Laser Power and Irrigation Rate During Ureteroscopy: In Vivo Porcine Assessment With a Ho:YAG Laser

OBJECTIVE

To map thermal safety boundaries during ureteroscopy (URS) with laser activation in two in vivo porcine subjects to better understand the interplay between laser power, irrigation rate, and fluid temperature in the collecting system.

METHODS

URS was performed in two in vivo porcine subjects with a prototype ureteroscope containing a thermocouple at its tip. Up to 6 trials of 60 seconds laser activation were carried out at each selected power setting and irrigation rate. Thermal dose was calculated for each trial, and laser power-irrigation rate parameter pairs were categorized based on number of trials that exceeded a thermal dose of 120 equivalent minutes.

RESULTS

The collecting fluid temperature was increased with greater laser power and slower irrigation rate. In the first porcine subject, 25 W of laser power could safely be applied if irrigation was at least 15 mL/min, and 48 W with at least 30 mL/min. Intermediate values followed a linear curve between these bounds. For the second subject, where the calyx appeared larger, 15 W laser power required 9 mL/min irrigation, 48 W required 24 mL/min, and intermediate points also followed a near-linear curve.

CONCLUSION

This study validates previous bench research and provides a conceptual framework for selection of safe laser lithotripsy settings and irrigation rates during URS with laser lithotripsy. Additionally, it provides insight and guidance for future development of thermal mitigation strategies and devices.

Holmium and Thulium Fiber Laser Safety in Endourological Practice: What Does the Clinician Need to Know?

PURPOSE OF REVIEW: To summarise the literature on laser safety during endourological practice. RECENT FINDINGS: Holmium and Thulium Fiber laser are the two main energy sources in the current clinical practice. The latter may have superior properties, but more clinical studies are needed to formally establish this. Laser injury to urothelium is more dependent on user experience rather than laser type. Smaller laser fibres allow for lower intra-renal temperature profiles. Operators should pay close attention to laser technique including maintaining the safety distance concept and only firing the laser when tip is clearly in view. When adjusting laser settings, pay close attention to resultant power given the associated heat changes. Prolonged periods of laser activation are to be avoided for the same reason. Outflow can be manipulated such as with access sheath to mitigate temperature and pressure changes. There is still limited evidence to support the mandate for compulsory use of eye protection wear during laser lithotripsy. Lasers are the gold standard energy source for stone lithotripsy. However, the safe clinical application of this technology requires an understanding of core principles as well as awareness of the safety and technical aspects that can help in protecting patient, surgeon and operating staff.

Effect of outflow resistance on intrarenal pressure at different irrigation rates during ureteroscopy: in vivo evaluation

To maintain visualization and control temperature elevation during ureteroscopy, higher irrigation rates are necessary, but this can increase intrarenal pressure (IRP) and lead to adverse effects like sepsis. The IRP is also dependent on outflow resistance but this has not been quantitatively evaluated in a biological system. In this study, we sought to characterize the IRP as a function of irrigation rate in an in vivo porcine model at different outflow resistances. Ureteroscopy was performed in a porcine model with a 9.5 Fr prototype ureteroscope containing a pressure sensor. A modified ureteral access sheath (UAS) (11/13 Fr, 36 cm) was configured to adjust outflow resistance. IRP-irrigation rate curves were generated at four different outlet resistances representing different outflow scenarios. At lower irrigation rates, the pressure change in response to increased irrigation was gradual and non-linear, likely reflecting a "compliant" phase of the renal collecting system. Once IRP reached the range of 35-50 cm H2O, the pressure increased in a linear fashion with irrigation rate, suggesting that the distensibility of the collecting system had become saturated. The relationship between IRP and irrigation rate becomes linear during in vivo porcine studies once the initial compliance of the system is saturated. IRP is more sensitive to changes in irrigation rate in systems with higher outflow resistance. The modified UAS is a novel research tool which allows variance of outflow resistance to mimic different clinical scenarios. Knowledge of outflow resistance may simplify the decision to use an UAS.

Lasers for stone lithotripsy: advantages/disadvantages of each laser source

PURPOSE

The purpose of this article was to make a narrative review of the literature in search of all articles regarding thulium:yttrium-aluminium-garnet (YAG), thulium laser fiber (TFL) and holmium:YAG (Ho:YAG) for lithotripsy from 2020 to 2023. A selection of articles of special interest and best evidence was made in order to give a better perspective on their advantages and disadvantages.

RECENT FINDINGS

New Ho:YAG technologies of as high power, high frequency and pulsed modulations have shown promising results for lithotripsy by reducing retropulsion with good ablation efficiency. High peak power makes it particularly good for percutaneous nephrolithotomy. High intrarenal temperatures and correct setting are still concerning points.TFL has arrived to be one of the main players in flexible ureteroscopy. Being highly efficient and quick, and by producing micro-dusting the laser is quickly heading to become a gold standard. The new pulsed Thulium YAG is the newest laser. For now, only in-vitro studies show promising results with efficient lithotripsy. As the peak power lies between Ho:YAG and TFL it may be able to adequately perform when needing and low power lithotripsy.

SUMMARY

Several new technologies have been developed in the last years for stone lithotripsy. All being efficient and safe if well used. Different advantages and disadvantages of each laser must be taken into consideration to give each laser the proper indication.

Ureteroscopy and lasertripsy with pop dusting using high power holmium laser for large urinary stones > 15 mm: 6.5-year prospective outcomes from a high-volume stone center

INTRODUCTION

Ureteroscopy and stone lasertripsy (URSL) is a recognized technique for treatment of urinary tract stones. Holmium:Yag laser has been successfully used for this purpose for the last two decades. More lately, pulse modulation with Moses technology and high power lasers have been introduced with the result of faster and more efficient stone lasertripsy. Pop dusting is a two-stage combined treatment using a long pulse Ho:YAG laser, initially in contact mode with the stone 'dusting' (0.2-0.5 J/40-50 Hz) followed by non-contact mode 'pop-dusting' (0.5-0.7 J/20-50 Hz). We wanted to look at the outcomes of lasertripsy for renal and ureteric stones using a high-power laser machine.

METHODS

Over a period of 6.5 years (January 2016-May 2022), we prospectively collected data for patients undergoing URSL for stones larger than 15 mm treated using high power Ho:YAG laser (60W Moses or 100W laser). Patient parameters, stone demographics and outcomes of URSL were analyzed.

RESULTS

A total of 201 patients, underwent URSL for large urinary stones. In 136 patients (61.6%) stones were multiple and the mean single and cumulative stone size was 18 mm and 22.4 mm respectively. A pre- and post-operative stent was placed in 92 (41.4%) and 169 (76%) respectively. The initial and final stone free rate (SFR) were 84.5% and 94% respectively and 10% patients underwent additional procedure to achieve stone free status. 7 (3.9%) complications were recorded, all related to UTI/sepsis, with 6 Clavien II and 1 Clavien IVa complication.

CONCLUSION

Dusting and pop-dusting has shown to be successful and safe with the ability to treat large, bilateral or multiple stones with low retreatment and complication rates.

Comparison of the efficacy and safety of holmium laser with the Moses technology and regular mode for stone treatment: a systematic review and meta-analysis

BACKGROUND

As a new pulse modality of holmium laser in retrograde intrarenal stone surgery, the MOSES technique can reduce the possibility of stone drifting and help to powder kidney stones in vitro and in animal experiments. However, there remains controversy about whether the MOSES mode needs to be used instead of the regular mode in clinical practice. This meta-review was conducted to evaluate the clinical efficacy and safety of MOSES technology for stone disease.

METHODS

PubMed, Embase, Web of Science, Cochrane Library, and CNKI were searched for relevant studies until September 2022, with 1 RCT and 6 nonrandomized studies included. We pulled data on adverse events, success rates and operative time to analyze based on the random effect model.

RESULTS

We found that using MOSES mode could shorten the operative time (standard mean difference [SMD] - 0.43; 95% confidence interval [CI] - 0.79 to  - 0.08; P = 0.016) than regular mode especially in a small sample study or in the Asian area. When the number of women is smaller than the number of men, the reduction of the duration was also significant. Stone-free rates of the two modes had no difference (relative risk [RR] 1.06; 95% CI 0.99-1.12; P = 0.30), and there was no publication bias. In terms of safety, no significant difference in complications was detected between the two approaches (RR 0.85; 95% CI 0.48-1.53; P = 0.81) without significant heterogeneity.

CONCLUSION

MOSES mode holmium laser was superior to the regular mode laser in terms of procedure time. There was no large disparity in stone-free rates or complications between the two modes. However, our conclusions should be confirmed in prospective studies with high evidence.

Comparison of Efficacy and Safety of Laparoscopic Holmium laser Lithotripsy and Laparoscopic Bile Duct Exploration for Bile Duct Stones: A Systematic Review and Meta-Analysis

BACKGROUND

Laparoscopic holmium laser lithotripsy (LHLL) has been used to treat bile duct stones with unclear outcomes. A meta-analysis was conducted to investigate the LHLL and laparoscopic bile duct exploration (LBDE) efficacy and safety in treating bile duct stones.

METHODS

The correlational studies were searched databases, such as PubMed, Embase, Cochrane Library, Web of Science, CNKI, Wanfang, and VIP, to identify eligible studies from inception to July 2022. The dichotomous and continuous outcomes were evaluated using odds ratio (OR), risk difference (RD) and weighted mean difference (WMD) with 95% confidence intervals (CIs). Stata 15.0 and Review Manager 5.3 software helped in data analyses.

RESULTS

A total of 23 studies with 1,890 patients, primarily from China, were included. The results indicated that operation time (WMD = - 26.94; 95% CI:(- 34.30, - 19.58); P < 0.00001), estimated blood loss (WMD = - 17.97; 95% CI: (- 22.94, - 13.00); P = 0.002), rate of residual stone (OR = 0.15, 95%CI: (0.10, 0.23); P < 0.00001), length of hospital stay (WMD = - 2.88; 95% CI:(- 3.80, - 1.96); P < 0.00001) and time to bowel function recovery (WMD = - 0.59; 95% CI: (- 0.76, - 0.41); P < 0.00001) had statistically significant differences between the two groups. In postoperative complications, biliary leakage (RD = -0.03; 95% CI: (- 0.05, -0.00); P = 0.02), infection (RD = - 0.06; 95% CI: (- 0.09,- 0.03); P < 0.00001) and Hepatic injury (RD = - 0.06; 95% CI: (- 0.11, - 0.01); P = 0.02) revealed statistically significant differences. However, no significant differences were observed in biliary damage (RD = - 0.03; 95% CI: (- 0.06, 0.00); P = 0.06) and hemobilia (RD = - 0.03; 95% CI: (- 0.06, 0.00); P = 0.08).

CONCLUSION

The current meta-analysis indicated that LHLL could be more effective and safer than LBDC. However, these results should be confirmed with a larger sample size and rigorously designed randomized controlled trials.

Temperature change during laser upper-tract endourological procedures: current evidence and future perspective

PURPOSE OF REVIEW

To examine the most recent data on temperatures produced during laser lithotripsy and to provide several strategies for maintaining lower values and reducing the risk of complications during endourological treatment.

RECENT FINDINGS

Endourologists have access to a wide range of alternatives with the help of the holmium: yttrium-aluminum-garnet (Ho:YAG), thulium: yttrium-aluminum-garnet (TM:YAG), and thulium fiber laser (TFL) that compose a robust and adaptable laser lithotripsy armamentarium. Nevertheless, the threat of thermal damage increases as the local temperature rises with high total power. Most endourologists are not familiar with normal and pathological temperature ranges, how elevated temperatures affect perioperative problems, or how to avoid them.

SUMMARY

Increased temperatures experienced during laser lithotripsy may affect the course of the healing process. All lasers display a safe temperature profile at energies below 40 W. At equal power settings, Ho:YAG, Tm:YAG, and TFL lasers change the temperature comparably. Shorter on/off laser activation intervals, chilled irrigation, open irrigation systems, and UASs all aid in maintaining acceptable temperatures.

Effectiveness and Safety of Thulium Fiber Laser in the Conservative Management of Patients with Upper Tract Urothelial Carcinoma

Background

Few clinical data are available on thulium fiber laser (TFL) and conservative treatment of upper urinary tract urothelial carcinoma (UTUC).

Objective

To assess the effectiveness and safety of TFL in the conservative treatment of UTUC in terms of both tumor ablation and complication rates in a short-term follow-up.

Design setting and participants

Retrospective data were collected from all patients who underwent endoscopic management of UTUC between January 2021 and April 2022. All patients with nonmetastatic UTUC who were deemed suitable candidates (low- and high-grade disease) for conservative treatment were reviewed.

Intervention

All patients underwent ureteroscopy with biopsy and at 2, 6, and 12 mo after the first surgery. UTUC ablation was achieved using TFL.

Outcome measurements and statistical analysis

Clinical data were collected in a dedicated database. Intra- and postoperative outcomes were assessed. A descriptive statistical analysis was performed.

Results and limitations

In total, 28 patients were evaluated. Thirteen patients (46.4%) were included in the low-risk UTUC treatment group and 15 (53.6%) in the high-risk group. The mean tumor size was 15.3 ± 5.7 mm. Biopsy showed low- and high-grade UTUCs in 19 and eight patients, respectively. Only one biopsy was inconclusive for achieving a diagnosis. At the second procedure biopsy, no tumor was found in 19 cases (70.4%), whereas seven had tumors confirmed (25.9%). To date, 23 and 17 out of 26 patients completed the 6- and 12-mo follow-up, respectively. UTUC recurrence was detected in five of 23 patients (21.7%) and in three of 17 patients (17.7%) at 6 and 12 mo, respectively. A total of 95 procedures were performed. No intraoperative complications were observed. In ten of the 95 procedures (10.5%), Clavien-Dindo grade I-II postoperative complications were experienced. Only one grade IIIB postoperative complication was noted.

Conclusions

TFL is a safe and effective technique for conservative treatment of UTUC in a short-term follow-up. Optimal tumor ablation and fine hemostatic control were achieved without major complications.

Patient summary

In this study, we looked at the outcomes of upper urinary tract tumors conservatively treated with the new thulium fiber laser (TFL). We conclude that TFL represents a safe and effective technique for the treatment of this kind of tumors in a short-term follow-up.

Cavitation erosion by shockwave self-focusing of a single bubble

The ability of cavitation bubbles to effectively focus energy is made responsible for cavitation erosion, traumatic brain injury, and even for catalyse chemical reactions. Yet, the mechanism through which material is eroded remains vague, and the extremely fast and localized dynamics that lead to material damage has not been resolved. Here, we reveal the decisive mechanism that leads to energy focusing during the non-spherical collapse of cavitation bubbles and eventually results to the erosion of hardened metals. We show that a single cavitation bubble at ambient pressure close to a metal surface causes erosion only if a non-axisymmetric energy self-focusing is at play. The bubble during its collapse emits shockwaves that under certain conditions converge to a single point where the remaining gas phase is driven to a shockwave-intensified collapse. We resolve the conditions under which this self-focusing enhances the collapse and damages the solid. High-speed imaging of bubble and shock wave dynamics at sub-picosecond exposure times is correlated to the shockwaves recorded with large bandwidth hydrophones. The material damage from several metallic materials is detected in situ and quantified ex-situ via scanning electron microscopy and confocal profilometry. With this knowledge, approaches to mitigate cavitation erosion or to even enhance the energy focusing are within reach.

European Association of Urology Section of Urolithiasis and International Alliance of Urolithiasis Joint Consensus on Retrograde Intrarenal Surgery for the Management of Renal Stones

BACKGROUND

Retrograde intrarenal surgery (RIRS) has become the preferred treatment modality for nephrolithiasis. However, because of ongoing uncertainties regarding the optimal perioperative management, operative technique, and postoperative follow-up, as well as a lack of standardization for outcome reporting, consensus is needed to achieve more uniform clinical practice worldwide.

OBJECTIVE

To develop recommendations for RIRS on the basis of existing data and expert consensus.

DESIGN, SETTING, AND PARTICIPANTS

A protocol-driven, three-phase study was conducted by the European Association of Urology Section of Urolithiasis (EULIS) and the International Alliance of Urolithiasis (IAU). The process included: (1) a nonsystematic review of the literature to define domains for discussion; (2) a two-round modified Delphi survey involving experts in this field; and (3) an additional group meeting and third-round survey involving 64 senior representative members to formulate the final conclusions.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The results from each previous round were returned to the participants for re-evaluation of their decisions during the next round. The agreement threshold was set at 70%.

RESULTS AND LIMITATIONS

The panel included 209 participants who developed 29 consensus statements on the following topics of interest: (1) perioperative infection management; (2) perioperative antithrombotic therapy; (3) fundamentals of the operative technique; and (4) standardized outcome reporting. Although this consensus can be considered as a useful reference for more clinically oriented daily practice, we also acknowledge that a higher level of evidence from further clinical trials is needed.

CONCLUSIONS

The consensus statements aim to guide and standardize clinical practice and research on RIRS and to recommend standardized outcome reporting.

PATIENT SUMMARY

An international consensus on the best practice for minimally invasive surgery for kidney stones was organized and developed by two international societies. It is anticipated that this consensus will provide further guidance to urologists and may help to improve clinical outcomes for patients.

Glossary of pre-settings given by laser companies: no consensus!

INTRODUCTION

Since the construction of the first laser, many companies around the world have contributed to the development of new lasers technologies. To be user-friendly, some companies have developed a pre-setting mode in their laser devices. We aimed to review and compare all laser companies' pre-settings (PS) already established in the market.

MATERIALS AND METHODS

An online search of holmium:YAG (Ho:YAG) and thulium fiber laser (TFL) devices was carried out. Manual and PS mode, pulse width and pulse modulation technology data were collected. The PS parameters were collected directly from the brochure devices or by asking the companies consulting agents.

RESULTS

Thirty-nine laser devices were analyzed (33 Ho:YAG and 6 TFL). The power range varies from 15 to 152 W and 35 W to 60 W for Ho:YAG and TFL, respectively. PS are present in 66% of Ho:YAG lasers and the 33% of TFL. Long-pulse modes can be modified in 12 Ho:YAG and 1 TFL lasers. The median (IQR) PS for dusting stones with Ho:YAG laser is 0.4 J (0.2-1), 21.5 Hz (5-120), and 10 W (1.5-28) for energy, frequency and power, respectively; for Ho:YAG fragmentation is 0.8 J (0.3-5), 10 (3-15) Hz and 5 (1.5-50) W for energy, frequency, and power, respectively; and for popcorn is 0.8 J (0.4-1.2), 10 Hz (6-15) and 5 W (4-18) for energy, frequency, and power, respectively. Dusting and fragmentation mode of Rocamed MH01 and EMS LaserClast 35 are programmed according to the stone type. Most of these settings do not depend on the size of the fiber being used nor the location and type of stone. For TFL, the pre-sets are divided in bladder stone, dusting, fine dusting, fragmentation, and ureteral stone.

CONCLUSION

There is a huge variability regarding pre-sets offered by companies because there is no consensus. Pre-sets should provide a range to work efficacy and safety.

The Effects of Scanning Speed and Standoff Distance of the Fiber on Dusting Efficiency during Short Pulse Holmium: YAG Laser Lithotripsy

To investigate the effects of fiber lateral scanning speed across the stone surface (v_fiber) and fiber standoff distance (SD) on dusting efficiency during short pulse holmium (Ho): YAG laser lithotripsy (LL), pre-soaked BegoStone samples were treated in water using 0.2 J/20 Hz at SD of 0.10~0.50 mm with v_fiber in the range of 0~10 mm/s. Bubble dynamics, pressure transients, and stone damage were analyzed. To differentiate photothermal ablation vs. cavitation damage, experiments were repeated in air, or in water with the fiber tip at 0.25 mm proximity from the ureteroscope end to mitigate cavitation damage. At SD = 0.10 mm, the maximum dusting efficiency was produced at v_fiber = 3.5 mm/s, resulting in long (17.5 mm), shallow (0.15 mm), and narrow (0.4 mm) troughs. In contrast, at SD = 0.50 mm, the maximum efficiency was produced at v_fiber = 0.5 mm/s, with much shorter (2.5 mm), yet deeper (0.35 mm) and wider (1.4 mm), troughs. With the ureteroscope end near the fiber tip, stone damage was significantly reduced in water compared to those produced without the ureteroscope. Under clinically relevant v_fiber (1~3 mm/s), dusting at SD = 0.5 mm that promotes cavitation damage may leverage the higher frequency of the laser (e.g., 40 to 120 Hz) and, thus, significantly reduces the procedure time, compared to at SD = 0.1 mm that promotes photothermal ablation. Dusting efficiency during short pulse Ho: YAG LL may be substantially improved by utilizing an optimal combination of v_fiber, SD, and frequency.

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

Comprehensive endoscopic management of impacted ureteral stones: Literature review and expert opinions

Treatment of urolithiasis, a benign disease, requires high efficacy and safety. Endoscopic treatment of impacted ureteral stones remains a challenging procedure for urologists, despite recent remarkable advances in surgical technology in treatment of urolithiasis. The success rate of endoscopic treatment in patients with impacted stones is reported to be lower than that in patients with nonimpacted stones. Moreover, the presence of stone impaction is associated with high rates of intraoperative and postoperative complications. The best management for patients with impacted ureteral stones should therefore be devised based on the latest knowledge and techniques. The present review focuses on the preoperative prediction of stone impaction, the safest and most effective endoscopic surgical procedures, and the most appropriate management for postoperative ureteral strictures. We overview comprehensive endoscopic management for impacted ureteral stones based on literature review and expert opinions.

Theoretical and experimental evaluation of the distance dependence of fiber-based fluorescence and reflection measurements for laser lithotripsy

OBJECTIVES

In laser lithotripsy, a green aiming beam overlying the infrared (IR) treatment radiation gives rise to reflection and fluorescence signals that can be measured via the treatment fiber. While stone autofluorescence is used for target detection, the condition of the fiber can be assessed based on its Fresnel reflection. For good applicability, fluorescence detection of stones should work even when the stone and fiber are not in direct contact. Fiber breakage detection, on the other hand, can be falsified if surfaces located in front of the fiber reflect light from the aiming laser back into it. For both applications, therefore, a fundamental investigation of the dependence of the signal amplitude on the distance between fiber and surface is important.

METHODS

Calculations of the signal drop of fluorescence or diffuse and specular reflection with increasing fiber distance were performed using ray tracing based on a simple geometric model for different fiber core diameters. Reflection signals from a mirror, diffuse reflector, human calculi, and porcine renal tissue placed in water were measured at varying distances (0 - 5 mm). For human calculi, fluorescence signals were recorded simultaneously.

RESULTS

The calculations showed a linear signal decrease down to ~60% of the maximum signal (fiber in contact). The distance z at which the signal drops to for example 50% depends linearly on the diameter of the fiber core. For fibers used in lithotripsy and positioned in water,z_50%ranges from 0.55 mm (200 µm core diameter) to 2.73 mm (1 mm core diameter). The calculations were in good agreement with the experimental results.

CONCLUSIONS

The autofluorescence signals of stones can be measured in non-contact mode. Evaluating the Fresnel signal of the end face of the fiber to detect breakage is possible unless the fiber is situated less than some millimeters to reflecting surfaces.

Role of low- versus high-power laser in the treatment of lower pole stones: prospective non-randomized outcomes from a university teaching hospital

Introduction:

Ureteroscopy and laser stone fragmentation [flexible ureteroscopy and laser lithotripsy (FURSL)] has risen over the last two decades. Laser technology has also evolved over the time, shifting from low- to high-power lasers with the addition of MOSES technology that allows for ‘dusting and pop-dusting’ of stones. The aim of the study was to look at the outcomes of FURSL in lower pole stones (LPS) using low- and high-power lasers.

Patient and Methods:

In this study, we compared the outcomes of low-power holmium laser (group A, 20 W) and high-power holmium laser (group B, including both 60 W MOSES integrated system and 100 W lasers) for all patients with LPS treated with laser lithotripsy. Data were collected for patient demographics, stone location, size, pre- and postoperative stent, length of stay, complications and stone free rate (SFR).

Results:

A total of 284 patients who underwent FURSL procedure for LPS were analysed (168 group A, 116 group B). Outcomes showed that compared with group A, group B had a higher SFR (91.6% versus 96.5%, p = 0.13) and shorter operative time (52 versus 38 min, p < 0.001). The median length of stay was <24 h in all groups (day-case procedures). The complication rate was comparable between the two groups but with more infectious complications (n = 7) noted in group A compared with group B (n = 3) (p = 0.53).

Conclusion:

Compared with low-power laser, the use of high-power laser for LPS significantly reduced the use of ureteral access sheath (UAS), postoperative stent and procedural time. Although non-statistically significant, the SFR was higher in the high-power group even for relatively larger stone sizes, which was also reflected in a reduction of sepsis-related complication rates with these lasers.

The efficacy of different alveolar recruitment maneuvers in holmium laser lithotripsy surgery under general anesthesia using a laryngeal mask

Background

Alveolar recruitment maneuvers (ARMs) is an important part of lung-protective ventilation strategies (LPVSs), but the optimal duration and interval Remain unclear.

Methods

Patients:252 patients who underwent holmium laser lithotripsy surgery and meet inclusion criteria were included and randomized into three groups based on the duration and frequency of ARMs (Regular, one 30 s ARM (RARMs); Improved and intermittent, three 10s ARMs (IARMs); and Control (C), no ARMs).Interventions: Groups R and I received ARMs at 20 cmH2O pressures every 30 min. All patients received the same anesthesia and mechanical ventilation. Measurements:Outcomes included heart rate and mean arterial pressure changes during ARMs and postoperative pulmonary complications (PPCs) within the first 7 postoperative days.

Main results

Incidences of PPCs in groups R(7.1%) and I (5.0%)were slightly lower than those in group C (8.9%).This indicated the potential to reduce lung injury. Heart rate and mean arterial pressure fluctuations during ARMs were significantly higher in groups R and I than in group C (P < 0.01). The rate of blood pressure decrease was significantly higher in group R than in group I (P < 0.01).

Conclusions

IARMs can reduce cycle fluctuations than RARMs in patients Undergoing holmium laser lithotripsy surgery with laryngeal mask general anesthesia. Low tidal volume ventilation and low PEEP combined with ARM did not significantly reduce the incidence of PPCs in healthy lung patients, but tended to reduce lung injury.

Trial registration

The study was registered on the Chinese Clinical Trial Registry.

(ChiCTR2000030815,15/03/2020). This study was approved by the ethics committee of Chengdu Fifth People’s Hospital with approval number(2020–005(Study)-1).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-022-01664-y.

Cavitation Plays a Vital Role in Stone Dusting During Short Pulse Holmium:YAG Laser Lithotripsy

Objective: To investigate the mechanism of stone dusting in Holmium (Ho): YAG laser lithotripsy (LL). Materials and Methods: Cylindrical BegoStone samples (6 × 6 mm, H × D) were treated in water using a clinical Ho:YAG laser lithotripter in dusting mode (0.2-0.4 J with 70-78 μs in pulse duration, 20 Hz) at various fiber tip to stone standoff distances (SD = 0, 0.5, and 1 mm). Stone damage craters were quantified by optical coherence tomography and bubble dynamics were captured by high-speed video imaging. To differentiate the contribution of cavitation vs thermal ablation to stone damage, three additional experiments were performed. First, presoaked wet stones were treated in air to assess stone damage without cavitation. Second, the laser fiber was advanced at various offset distances (OSD = 0.25, 1, 2, 3, and 10 mm) from the tip of a flexible ureteroscope to alter the dynamics of bubble collapse. Third, stones were treated with parallel fiber to minimize photothermal damage while isolating the contribution of cavitation to stone damage. Results: Treatment in water resulted in 2.5- to 90-fold increase in stone damage compared with those produced in air where thermal ablation dominates. With the fiber tip placed at OSD = 0.25 mm, the collapse of the bubble was distracted away from the stone surface by the ureteroscope tip, leading to significantly reduced stone damage compared with treatment without the scope or with scope at large OSD of 3-10 mm. The average crater volume produced by parallel fiber orientation at 0.2 J after 100 pulses, where cavitation is the dominant mechanism of stone damage, was comparable with those produced by using perpendicular fiber orientation within SD = 0.25-1 mm. Conclusion: Cavitation plays a dominant role over photothermal ablation in stone dusting during short pulse Ho:YAG LL when 10 or more pulses are delivered to the same location.

Generated temperatures and thermal laser damage during upper tract endourological procedures using the holmium: yttrium-aluminum-garnet (Ho:YAG) laser: a systematic review of experimental studies

PURPOSE

To perform a review on the latest evidence related to generated temperatures during Ho:YAG laser use, and present different tools to maintain decreased values, and minimize complication rates during endourological procedures.

METHODS

We performed a literature search using PubMed, Scopus, EMBASE, and Cochrane Central Register of Controlled Trials-CENTRAL, restricted to original English-written articles, including animal, artificial model, and human studies. Different keywords were URS, RIRS, ureteroscopy, percutaneous, PCNL, and laser.

RESULTS

Thermal dose (t43) is an acceptable tool to assess possible thermal damage using the generated temperature and the time of laser exposure. A t43 value of more than 120 min leads to a high risk of thermal tissue injury and at temperatures higher than 43 °C Ho:YAG laser use becomes hazardous due to an exponentially increased cytotoxic effect. Using open continuous flow, or chilled irrigation, temperatures remain lower than 45 °C. By utilizing high-power (> 40 W) or shorter laser pulse, temperatures rise above the accepted threshold, but adding a ureteral access sheath (UAS) helps to maintain acceptable values.

CONCLUSIONS

Open irrigation systems, chilled irrigation, UASs, laser power < 40 W, and shorter on/off laser activation intervals help to keep intrarenal temperatures at accepted values during URS and PCNL.