Ho: YaG laser lithotripsy: recent innovations

[Thulium or holmium laser or both: where will the journey take us?]

The Holmium:YAG laser has been the gold standard for laser lithotripsy over the past three decades and, since the late 1990s, also for prostate enucleation. Pulsed thulium fibre lasers (TFL) demonstrated their efficacy in in-vitro experiments and were introduced to the market a few years ago. Initial clinical results for TFL in lithotripsy and enucleation are very promising. In addition to TFL, a pulsed Thulium:YAG solid-state laser has been introduced, but clinical data for this laser are currently limited. This article aims to review the key technological differences between Ho:YAG lasers and pulsed thulium lasers and compare/discuss the initial clinical results for stone lithotripsy and laser enucleation.In-vitro studies have demonstrated the technical superiority of TFL compared with Ho:YAG lasers. However, as TFL is still a new technology, only limited studies are available to date, and optimal settings for lithotripsy have not been established. For enucleation, the differences of TFL compared with a high-power Ho:YAG laser seem to be clinically irrelevant. Initial studies on pulsed Tm:YAG lasers show good results, but there continues to be a lack of comparative studies.Based on the current literature, pulsed thulium lasers have the potential of being an alternative to Ho:YAG lasers. However, further studies are necessary to determine the optimal laser technology for enucleation and lithotripsy of urinary stones, considering all parameters, including efficacy, safety, and cost.

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.

Flexible ureteroscopic treatment of kidney stones: How do the new laser systems change our concepts?

Objective

Flexible ureteroscopy (fURS) has become a widely accepted and effective technique for treating kidney stones. With the development of new laser systems, the fURS approach has evolved significantly. This literature review aims to examine the current state of knowledge on fURS treatment of kidney stones, with a particular focus on the impact of the latest laser technologies on clinical outcomes and patient safety.

Methods

We conducted a search of the PubMed/PMC, Web of Science Core Collection, Scopus, Embase (Ovid), and Cochrane Databases for all randomized controlled trial articles on laser lithotripsy in September 2023 without time restriction.

Results

We found a total of 22 relevant pieces of literature. Holmium laser has been used for intracavitary laser lithotripsy for nearly 30 years and has become the golden standard for the treatment of urinary stones. However, the existing holmium laser cannot completely powder the stone, and the retropulsion of the stone after the laser emission and the thermal damage to the tissue have caused many problems for clinicians. The introduction of thulium fiber laser and Moses technology brings highly efficient dusting lithotripsy effect through laser innovation, limiting pulse energy and broadening pulse frequency.

Conclusion

While the holmium:yttrium-aluminum-garnet laser remains the primary choice for endoscopic laser lithotripsy, recent technological advancements hint at a potential new gold standard. Parameter range, retropulsion effect, laser fiber adaptability, and overall system performance demand comprehensive attention. The ablation efficacy of high-pulse-frequency devices relies on precise targeting, which may pose practical challenges.

Simultaneously combining a thulium fiber laser and holmium:YAG laser in vacuum-assisted mini-endoscopic combined intrarenal surgery on a complex renal calculus: A case report

Employing percutaneous nephrolithotomy to manage a complex renal calculus has always been challenging due to the blood transfusion requirement and the frequent necessity of using multiple access tracts. We report a novel treatment modality in the case of a 65-year-old male with a complex, large-volume renal calculus who was successfully treated by vacuum-assisted miniaturized endoscopic combined intrarenal surgery using the combination of a thulium fiber laser in retrograde fashion with a holmium:YAG laser in antegrade fashion. The kidney stone was entirely cleared, and the patient fully recovered with no adverse event.

High-power Holmium:Yag lithotripsy in bladder urolithiasis: Is it safe and effective? A combined clinical and experimental study

Objective

To evaluate the efficacy and safety of Holmium: Yttrium-Aluminum-Garnet (Ho:YAG) laser in bladder lithotripsy using high-power settings > 100 W.

Materials and Methods

A combined experimental and clinical study was conducted. The Quanta Cyber: Ho 150 with a 550 μm Quanta optical fiber was utilized in all set-ups. Ablation rates for soft and hard artificial stones were tested in vitro using 100 W and 20 W power settings. In the experiment, a porcine bladder was used. The optical fiber was inserted through a rigid cystoscope, whilst a K-type thermocouple was inserted in the bladder dome. The tested high-power settings were 152 W, 120 W and 105 W. In every trial, the lasing time was over 60 s. In the clinical study, 35 patients underwent transurethral high-power bladder lithotripsy. Laser settings were set between 100 W and 150 W.

Results

Stone mass (stone weight) was significantly lower after stone ablation independently of the stone type or the laser settings. Significantly higher mass decrease and ablation rate were detected in high-power compared to low-power settings. In the experiment, the highest temperature recorded was 32°C at 152 W. At 120 W and 105 W, the peak temperatures didn't reach 30°C. In the clinical study, a stone-free rate of 100% and a mean operative time of 43 ± 18 min were reported. All patients stayed in the hospital for one day except for one who presented minor hematuria. Additional complications did not occur.

Conclusion

Ho:YAG laser lithotripsy > 100 W is an effective, fast and safe modality for the treatment of bladder calculi.

Observation and comparison of gas formation during holmium:YAG laser lithotripsy of cystine, uric acid, and calcium oxalate stones: a chromatographic and electron microscopic analysis

The primary aim of the present in vitro study is to analyze the chemical content of the bubbles occurring during the fragmentation of cystine stones with both the high-power and low-power holmium:YAG (Ho:YAG) lasers. The secondary aim is to discuss their clinical importance. Three types of human renal calculi calcium oxalate monohydrate (COM), cystine, and uric acid were fragmented with both low-power and high-power Ho:YAG lasers in separate experimental setups at room temperature, during which time it was observed whether gas was produced. After laser lithotripsy, a cloudy white gas was obtained, after the fragmentation of cystine stones only. A qualitative gas content analysis was performed with a gas chromatography-mass spectrometry (GC-MS) device. The fragments in the aqueous cystine calculi setup were dried and taken to the laboratory to be examined by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and X-ray diffraction analysis. No gas production was observed after fragmentation in the COM and uric acid stones. Free cystine, sulfur, thiophene, and hydrogen sulfide gas were produced by both low-power and high-power Ho:YAG laser lithotripsy of the cystine stones. In the SEM-EDX mapping analysis, a free cystine molecule containing 42.8% sulfur (S), 21% oxygen (O), 14.9% carbon (C), and 21% nitrogen (N) atoms was detected in the cystine stone experimental setup. The evidence obtained, which shows that hydrogen sulfide emerges in the gaseous environment during Ho:YAG laser fragmentation of cystine stones, indicates that caution is required to prevent the risk of in vivo production and toxicity.

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.

Dusting efficacy between the regular setting of holmium laser (Ho:YAG) versus Vapor Tunnel pulse modality for non-complex kidney stones

The new pulse modality Vapor-Tunnel™ (VT) consists of a very long pulse that uses the minimum peak power, causing the energy to pass through a previously created vapor channel or tunnel. The first part of the pulse creates a vapor channel, whereas the remaining energy is discharged immediately after, passing straight through the previously created tunnel. The aim of this study is to compare the dusting efficacy between Ho:YAG laser with long pulse and Ho:YAG laser with VT for non-complex kidney stones. A retrospective comparative study of 236 patients who underwent retrograde intrarenal surgery using Ho:YAG laser (long pulse vs. VT) was performed. Stone size, stone density, laser settings, laser emission time, and total operative time were recorded. We also assessed the lithotripsy efficacy (J/mm3). The stone-free rate was defined as the absence of stone fragments in a non-contrast abdominal computed tomography 4 weeks after the procedure. A total of 118 patients were included in each group. There was no significant difference in age, gender, and body mass index. Median stone volume (737 mm3 vs. 636 mm3) and stone density (788 HU vs. 656 HU) were higher in the VT group. Total energy used (14.5 J vs. 18.2 J), the laser emission time (20 min vs. 26 min), and the total operative time (79.5 min vs. 95 min) were significantly lower in the VT group. The stone-free rate was comparable between both groups (74.5% for VT and 66.1% for the long-pulse group, p = 0.15). When we evaluated the efficacy of laser lithotripsy, a significantly lower difference was obtained in the VT group (median 12.5 J/mm3 vs. median 23.1 J/mm3). The VT pulse modality was associated with decreased laser time and operative time. Additionally, it increased lithotripsy efficacy compared to Ho:YAG long pulse laser, but with a comparable free-stone rate.

First Clinical Experience of a Novel Pulsed Solid-State Thulium:YAG Laser during Percutaneous Nephrolithotomy

INTRODUCTION

Laser lithotripsy during Mini-PCNL is one treatment option in urinary stone disease. In recent years, a new era in stone treatment has been initiated with the introduction of new pulsed thulium lasers. The aim of this study was to investigate the safety and efficacy of laser lithotripsy with a new pulsed solid-state thulium:YAG laser during mini-PCNL.

MATERIALS AND METHODS

All patients, regardless of stone size, who were treated with a Mini-PCNL using the new pulsed thulium laser were prospectively enrolled. Operation times, stone size, laser time, and laser settings were noted. The stone-free rate was assessed postoperatively with sonography and either X-ray or computed tomography as a clinical standard. The complications were analyzed using the Clavien-Dindo classification.

RESULTS

A total of 50 patients with a mean age of 52 years were included. 31 (62 %) patients were male. The average stone size was 242.3 (±233.1) mm2 with an average density of 833 (±325) Hounsfield units. The mean operating time was 30.56 (±28.65) min, and the laser-on-time was 07:07 (± 07:08) min. The most commonly used settings were 0.4 J and 115 Hz (46 W). The mean total energy for stone ablation was 14,166 (±17,131) kJ. The total stone-free rate was 84 %, with an overall complication rate of 32% according to Clavien-Dindo (grade 1: n = 9, grade 2: n = 6, 3b: n = 1). In the group of patients with singular stones (n = 25), the stone-free rate was 88%.

SUMMARY

The new pulsed solid-state Thulium:YAG laser allows a safe and effective lithotripsy during Mini-PCNL. The stone-free rates were high regardless of stone size with a comparable low rate of complications.

Assessing critical temperature dose areas in the kidney by magnetic resonance imaging thermometry in an ex vivo Holmium:YAG laser lithotripsy model

PURPOSE

We aimed to assess critical temperature areas in the kidney parenchyma using magnetic resonance thermometry (MRT) in an ex vivo Holmium:YAG laser lithotripsy model.

METHODS

Thermal effects of Ho:YAG laser irradiation of 14 W and 30 W were investigated in the calyx and renal pelvis of an ex vivo kidney with different laser application times (t_L) followed by a delay time (t_D) of t_L/t_D = 5/5 s, 5/10 s, 10/5 s, 10/10 s, and 20/0 s, with irrigation rates of 10, 30, 50, 70, and 100 ml/min. Using MRT, the size of the area was determined in which the thermal dose as measured by the Cumulative Equivalent Minutes (CEM₄₃) method exceeded a value of 120 min.

RESULTS

In the calyx, CEM₄₃ never exceeded 120 min for flow rates ≥ 70 ml/min at 14 W, and longer t_L (10 s vs. 5 s) lead to exponentially lower thermal affection of tissue (3.6 vs. 21.9 mm²). Similarly at 30 W and ≥ 70 ml/min CEM₄₃ was below 120 min. Interestingly, at irrigation rates of 10 ml/min, t_L = 10 s and t_D = 10 s CEM₄₃ were observed > 120 min in an area of 84.4 mm² and 49.1 mm² at t_D = 5 s. Here, t_L = 5 s revealed relevant thermal affection of 29.1 mm² at 10 ml/min.

CONCLUSION

We demonstrate that critical temperature dose areas in the kidney parenchyma were associated with high laser power and application times, a low irrigation rate, and anatomical volume of the targeted calyx.

Lithotripsy devices for percutaneous nephrolithotomy (PNL) - new developments

PURPOSE OF REVIEW

Percutaneous nephrolithotomy (PNL) is the mainstay of surgery for renal calculi>2 cm or complex multiple calculi and is a technique that has been around since 1976. We review recent literature surrounding novel lithotripsy devices and technology used in PNL.

RECENT FINDINGS

At present, the Holmium:yttrium-aluminum-garnet (Ho:YAG) laser is widely accepted as the gold standard laser lithotripsy for PNL. SwissLithoClast Trilogy offers a range of probes with a trifecta of electromagnetic, ultrasonic energy with surgeon-controlled suction. The Olympus Shockpulse-SE is a similar lithotripter that relies on continuous ultrasonic energy with pulsed ballistic energy to break stones. Thulium Fiber Laser (TFL) offers an alternative laser energy source to the Holmium laser, which has been shown to be very effective at producing small stone fragments and dust. The Moses technology is another addition in a long list of improvements to the Ho:YAG laser, forming vaporization bubble through which more effective energy can be applied to stones.

SUMMARY

Trilogy, Shockpulse, TFL and Moses pulse modulation technology for the Holmium laser all provide improvements compared with older lithotripsy devices. In particular, they convey a safer, efficient and more effective way to manage and clear stones.

Alignment-insensitive end-pumped continuous-wave crossed-Porro prism Ho3+:YAG laser

A continuous-wave crossed-Porro prism Ho³⁺:YAG laser is presented and compared with a corresponding mirror resonator. A maximum output power of 30.7 W is reached with a slope efficiency of 67.4% with respect to the absorbed pump power. The laser output beam shows a very good beam quality of better than M² < 1.2 which clearly surpasses that of the mirror resonator. In terms of alignment sensitivity, the crossed-Porro prism resonator is superior to the mirror resonator due to the retro-reflective nature of the prisms in the axis around the apex.

MOSES™ pulse modulation technology versus conventional pulse delivery technology: the effect on irrigation fluid temperature during flexible ureteroscopy

To compare the effect of MOSES™ modulation technology to conventional pulse delivery technology on the irrigation fluid temperature (IFT) under different irrigation conditions during flexible ureteroscopy (FURS) in a live-anesthetized porcine model. For this experiment was used one female pig. A percutaneous access was obtained and a 30Fr sheath was placed inside the upper calyceal system. A thermocouple was inserted through the sheath to the upper calyx to record the effect on IFT during FURS. A Lumenis 120H Ho:YAG laser was used and the IFT was recorded during laser activation for 30 s at a laser power of 20 W, 40 W and 60 W under gravity and manual pump irrigation using MOSES™ and conventional pulse delivery technology. In the highest power settings the maximum IFT was achieved in 18 s under gravity irrigation (66.4 °C). It seems that there is no significant difference on IFT between MOSES and conventional mode on the IFT under different irrigation conditions during FURS at 20 W, 40 W and 60 W power settings. Furthermore, our results indicate that under manual pumping even high-power settings (40 W, 60 W) can be performed with safety. In the in vivo model, the MOSES™ pulse delivery technology does not have a significant difference in the maximal IFT in comparison to conventional pulse delivery technology during FURS in the same power settings. Manual pumping should be used to keep the IFT within safe limits.

Could retrograde intrarenal surgery be a safe and effective alternative to mini-percutaneous nephrolithotomy ın the management of relatively large (20-30 mm) stones? A critical evaluation

PURPOSE

To compare the outcomes of mini-percutaneous nephrolithotomy (mPCNL) and retrograde intrarenal surgery (RIRS) in patients with renal stones sizing 2-3 cm.

METHODS

A total of 566 patients from 6 institutions who underwent mPCNL (n = 440) and RIRS (n = 126) procedures were enrolled in our study. The retrospective patient cohort was reviewed and compared. Binary logistic regression analysis was performed to determine factors predicting success in the RIRS group.

RESULTS

The stone-free rates were 91.1 and 77% for the mPCNL and RIRS groups, respectively (p < 0.001). The auxiliary procedure rates were 4.5 and 39.7% in the mPCNL and RIRS groups, respectively (p < 0.001). Mean values of hemoglobin decrease, fluoroscopy time, and hospitalization time were significantly higher in the mPCNL group (p < 0.001). While the Clavien grade 1-2 complication rates were 10.9 and 34.1% (p < 0.001) in two groups, these values were 2.7 and 1.6% (p = 0.539), respectively, for Clavien grade 3-4 complication rates. Although three patients in the mPCNL group received blood transfusions, none of the patients in the RIRS groups were transfused. The stone location and stone density parameters were found to be the independent predictive factors for RIRS success.

CONCLUSIONS

mPCNL provided a higher stone-free rate, less need for the auxiliary procedure, and lower complication rates compared to RIRS in patients with 2-3 cm stones. Blood loss, radiation exposure, and a hospital stay of mPCNL can be significantly reduced with the RIRS technique in selected patients.

Primary impact of simultaneous use of double devices through one-working channel when performing flexible ureteroscope with ureteral access sheath for single ureteral stone: In bench and retrospective clinical study

OBJECTIVES

This study aimed to compare the simultaneous use of two devices versus a single device through a single working channel in flexible ureteroscopy using a ureteral access sheath for single ureteral stones.

METHODS

In a bench study, the time to (i) set laser fiber, (ii) exchange laser fiber and nitinol basket through working channel, and (iii) pull out the device from working channel were measured 10 times in each step. In a clinical study, 156 patients who underwent flexible ureteroscopy with a ureteral access sheath for a ureteral stone in middle and upper ureter between April 2019 and November 2021 were assessed. One device was used at a time for 79 patients (S-Group) and two were simultaneously used for 77 (D-Group). Surgical outcomes and complications were compared.

RESULTS

In the bench study, the mean time to change from laser fiber to basket and from basket to laser fiber through the working channel were 26.1 ± 3.7 s and 23.6 ± 2.0 s (p = 0.084), respectively, which were significantly longer than the laser setup time (p < 0.001). In the clinical study, although the stone-free rate was not significantly different between the groups (S-Group 89.8%, D-Group 93.5%; p = 0.412), the median operation time was significantly shorter (p < 0.001) and the rate of postoperative stenting was significantly lower (p = 0.002) in the D-Group. There were no significant between-group differences in intra- and post-operative complications.

CONCLUSION

The simultaneous use of two devices through a single working channel is safe and could help save the time needed to exchange the laser fiber and nitinol basket.

The impact of lasers in percutaneous nephrolithotomy outcomes: results from a systematic review and meta-analysis of randomized comparative trials

Background Percutaneous nephrolithotomy (PCNL) is the first choice treatment of renal stones larger than 2 cm. We aimed to evaluate if lasers perform as equal as non-laser devices in patients with kidney stones candidate to PCNL. Materials and methods A comprehensive literature search was performed in MEDLINE via PubMed, Scopus and Cochrane Central Register of Controlled Trials (CENTRAL) to assess the differences in the perioperative course, incidence of postoperative complications, and stone free-rate (SFR) in patients with kidney stones undergoing laser versus non-laser PCNL in randomized studies. The incidences of complications were pooled using the Cochran-Mantel-Haenszel Method with the random effect model and expressed as Risk Ratios (RR), 95% Confidence Intervals (CI), and p-values. Surgical time and length of stay were pooled using the inverse variance of the mean difference (MD) with a random effect, 95% CI, and p-values. Analyses were two-tailed, with a significance set at p ≤0.05. Results Six papers including 732 patients (311 patients undergoing holmium laser and 421 non-laser PCNL) were included in meta-analysis. Surgical time and postoperative stay were shorter in the non-laser group (MD:11.14, 95% CI:2.32-19.96, p=0.002; MD:-0.81, 95%CI:-2.18-0.57 p=0.25, respectively). SFR was significantly higher in the non-laser group (RR:1.08, 95% CI:1.01-1.15, p=0.03). Patients undergoing laser PCNL had a non-significant higher risk of postoperative fever >38°C (RR:0.64, 95%CI: .31-1.30, p=0.22). Transfusion rate did not differ between the two groups (RR:1.02, 95% CI:0.50-2.11 p=0.95). The need for stent positioning due to urine extravasation was higher risk in the laser group but the difference did not reach significance (RR:0.49, 95% CI:0.17-1.41 p=0.19). Conclusions Non-laser PCNL showed better perioperative outcomes and SFR as compared to holmium laser PCNL.

Multisensorial Assessment of Laser Effects on Shellac Applied on Wall Paintings

The assessment of five different laser treatments in the conservation of wall paintings was devised on the basis of the surface temperature monitoring by infrared thermography (IRT), ultraviolet-induced fluorescence-visible (UV-VIS) imaging, and optical coherence tomography (OCT). A series of yttrium-aluminum-garnet (YAG) lasers were tested for removal of shellac layers from wall painting mock-ups. The mock-ups were realized as buon fresco with different mineral based pigments (earths and iron oxide) on a lime- and sand-based mortar. After the carbonatation process, all the samples were treated with shellac (5% in ethanol). The effects of neodymium (Nd):YAG, holmium (Ho):YAG, and erbium (Er):YAG laser sources, in different operative modes, on average temperature of the surface, color, and morphology were inspected with complementary sensors. The results show the necessity to adopt a combined approach in establishing safe laser operating conditions to avoid any undesired effects induced on the artefacts by the laser treatments. We demonstrate, for the first time, the performance of the Ho:YAG laser in the removal of a conservation treatment.

Basic and advanced technological evolution of laser lithotripsy over the past decade: An educational review by the European Society of Urotechnology Section of the European Association of Urology

Laser disintegration of urinary stones is a cornerstone of urolithiasis treatment in the modern era. Despite the wide clinical use of stone lasers, basic and advanced technological achievements and developments are difficult to comprehend and interpret by the average urologist. A descriptive analysis of laser production and stone disintegration mechanisms was performed. We focused on physics of modern types of lithotripters, the construction of laser fibers, laser parameters, new modes, settings, and lithotripsy techniques. The main principle of laser emission remains the same since the first emitting laser was produced. Peak power density and short interaction time lead to photothermal effects responsible for stone disintegration. Modern lithotripters such as Holmium: YAG (low/high power, Moses technology) and thulium fiber laser show basic construction differences with the physical properties of the latter being superior, at least in in vitro studies. By adjusting lasing parameters, a wide spectrum of stone ablation from fragmentation to dusting can be achieved. New technology allows for the production of real dust. Knowledge of laser fiber construction and physical properties are useful in marketing and clinical use. Urologists should understand the physical and physiological background of the lasers used in their everyday practice for stone fragmentation.

Novel Biocompatible Adhesive to Remove Stone Dust: Usability Trial in a Kidney Model

Introduction and Objective: "Clinically insignificant residual fragments" are an independent predictive factor for recurrence of nephrolithiasis. To improve the stone-free rates (SFR), we tested the viability of a novel bioadhesive system for intrarenal embedding and retrieval of residual fragments <1 mm in a kidney model. Materials and Methods: All procedures were performed in a standardized setting, including a kidney model (Kidney module right, Samed GmbH, Dresden) in a plastic basin filled with water. We used a Viper URF flexible ureterorenoscope (fURS) (6.6/8F, Richard Wolf, Knittlingen). A mean amount of 138 mg (standard deviation [SD] ±32.2 mg) of sand grains (range, 0.2-0.8 mm) was inserted in renal calices of the kidney model. We assessed the extraction efficacy of fURS using the bioadhesive system. In total, eight different surgeons performed each one trial, respectively. The endoscopic and macroscopic SFR, the level of the surgeons' experience, and the overall time of stone retrieval were evaluated. Additionally, a survey of the participants was conducted, to assess the contentment with this novel system. Results: The extraction of the sand grains was only possible using the bioadhesive system, otherwise they were too small sized to grab with a retrieval basket. The total SFR was 84% (SD ±11.7%). The operation time (p = 0.052) and the percentage of extracted sand grains (p = 0.194) were not significantly different between experienced and less experienced surgeons. All participants stated that it was a promising technique, which they could imagine using on a daily basis. Conclusions: The bioadhesive system improves the SFR with fragments from 0.2 to 0.8 mm (0% vs 84%). Also, the performance of this operation is not dependent on the surgeon's experience level. This method might improve the SFR in difficult anatomic conditions, that is, lower calices or anomalous kidneys.

The optimal settings of holmium YAG laser in treatment of pediatric urolithiasis

The aim of this study is to present our experience on the use of the holmium:yttrium-aluminum-garnet (Ho:YAG) laser in pediatric patients for pediatric urolithiasis and describe the optimal settings. A total of 116 children who underwent urolithiasis treatment (percutaneous nephrolithotomy (PNL), ureterorenoscopy (URS), retrograde intrarenal surgery (RIRS)) were included. The mean age of the patients was 8.4 ± 5.2 years (1-18). The mean follow-up was 26 ± 8.8 months (9-45). There was no difference between the mean stone sizes of PNL and RIRS patients (p = 0.816). Operations were performed with 200, 272, and 365-μm fibers. In mini-URS, stone fragmentation was achieved with the energy settings set between 0.5 and 1 J and frequency set to > 8 Hz. In RIRS, fragmentation was achieved with the setting of 0.5-0.8 J at 10-20 Hz. Stone fragmentation was performed with energy settings of 0.8 to 2 J between 5 and 15 Hz for PNL. There was no significant difference between the stone-free rates of the PNL and RIRS (p = 0.150). Four postoperative complications occurred (Clavien II), which included febrile urinary infections in two patients who underwent mini-URS, one patient who underwent PNL, and one patient who underwent RIRS. Our results confirmed that Ho-YAG laser can be effectively used in children for stone treatment by using low-energy high-frequency settings for URS and RIRS and a high energy setting for PNL.

Thulium fiber laser utilization in urological surgery: A narrative review

The thulium fiber laser (TFL) is a novel technology under active investigation as an conceivable alternative to the Holmium:yttrium-aluminum-garnet (Ho:YAG) laser, which is currently the gold standard for an array of urologic procedures. The purpose of this review is to discuss the existing literature on the functionality and effectiveness of TFL in urological practice. We conducted a search of the PubMed, Medline, Web of Science Core Collection, SCOPUS, Embase (OVID), and Cochrane Databases for all full articles and systematic reviews on the TFL. We found a total of 35 relevant pieces of literature. The early research findings pertaining to the TFL exhibit numerous potential advantages over the Ho:YAG laser. In vitro and ex vivo studies have highlighted the TFL's ability to utilize smaller laser fibers, obtain faster stone ablation rates, and achieve less retropulsion when tested against the Ho:YAG laser in lithotripsy. Currently, there is limited in vivo research that investigates the utilization of the TFL. The in vivo results that are available, however, look promising both for laser lithotripsy and soft tissue ablation. Indeed, the existing literature suggests that the TFL has great potential and may possess numerous technological advantages over the Ho:YAG laser, especially in laser lithotripsy. Although these early studies are promising, randomized control trials are needed to assess the full applicability of the TFL in urology.

Lasers for stone treatment: how safe are they?

PURPOSE OF REVIEW

To update laser lithotripsy advances in regard to new laser types and technologies as well as review contemporary laser safety concerns.

RECENT FINDINGS

The high prevalence of urolithiasis and the continuing miniaturization of scopes has encouraged the growth of laser lithotripsy technology. The holmium:yttrium-aluminum-garnet (Ho:YAG) laser has been used for over 20 years in endourology and has been extensively studied. Holmium laser power output is affected by a number of factors, including pulse energy, pulse frequency, and pulse width. Several recent experimental studies suggest that the new dual-phase Moses 'pulse modulation' technology, introduced in high-power laser machines, carries a potential to increase stone ablation efficiency and decrease stone retropulsion. A newly introduced thulium fiber laser (TFL) has been adapted to a very small laser fiber size and is able to generate very low pulse energy and very high pulse frequency. Both of these technologies promise to play a larger role in laser lithotripsy in the near future. However, more experimental and clinical studies are needed to expand on these early experimental findings. Even though laser lithotripsy is considered safe, precautions should be taken to avoid harmful or even catastrophic adverse events to the patient or the operating room staff.

SUMMARY

The Ho:YAG laser remains the clinical gold standard for laser lithotripsy for over the last two decades. High-power Ho:YAG laser machines with Moses technology have the potential to decrease stone retropulsion and enhance efficiency of laser ablation. The new TFL has a potential to compete with and perhaps even replace the Ho:YAG laser for laser lithotripsy. Safety precautions should be taken into consideration during laser lithotripsy.

Assessing the Role of Light Absorption in Laser Lithotripsy by Isotopic Substitution of Kidney Stone Materials

Understanding the chemical characteristics of kidney stones and how the stone composition affects their fragmentation is key to improving clinical laser lithotripsy. During laser lithotripsy, two mechanisms may be responsible for stone fragmentation: a photothermal mechanism and/or microexplosion mechanism. Herein, we carry out an isotopic substitution of crystal H₂O with D₂O in calcium oxalate monohydrate and struvite stones to alter their optical properties to study the relationship between the absorption of the stones, at the wavelength of the Ho:YAG (2.12 μm) laser, and the fragmentation behavior. Changing the absorption of the stones at 2.12 μm changes the extent of fragmentation, whereas changing the absorption of the bulk medium has a negligible effect on fragmentation, leading to the conclusion that kidney stone ablation is dominated by a photothermal mechanism.

Efficacy and Safety of Holmium Laser Lithotripsy Under Local Anesthesia in the Treatment of Urethral Stones in Elderly Male Patients

The elderly population has been increasing significantly in our century. In our study, it was aimed to analyze the treatment results of elderly male patients who underwent holmium laser lithotripsy (HLL) for urethral stones under local anesthesia. We evaluated a total of 31 male patients, aged ≥65 years, diagnosed with urethral stones and treated with HLL under local anesthesia. We noted the demographic data and visual pain scores (VAS) of the patients and the duration of the operation and hospital stay. Our analysis involved both the success rates of the surgical procedure and the complication rates according to the modified Clavien classification. In addition. we determined the patients’ preoperative clinical status using the Charlson comorbidity index (CCI). The mean age of the patients was 71.65 ± 8.19 years. Acute urinary retention was the most common complaint (45.2%). Their mean scores were 7.68 ± 2.53 according to CCI. The average operation time was 15.48 ± 5.22 min and the VAS was 2.03 ± 1.08. All patients were stone-free and there was a marked improvement in their symptoms None of them stayed in the hospital for more than one day. We did not observe any Grade 3 or higher complications. In light of the data obtained in our study, we concluded that HLL is an effective and reliable method to treat urethral stones under local anesthesia in elderly male patients.

Feasibility of dusting and pop-dusting using high-power (100W) Holmium YAG (Ho:YAG) laser in treatment of paediatric stones: results of first worldwide clincial study

Introduction

As the role of paediatric ureteroscopy (URS) for stone disease increases, new methods of stone treatment such as dusting and pop-dusting have emerged. However, outcomes of treatment using these laser settings in paediatric age group is still largely unknown. We aimed to look at the feasibility and outcomes of URS and pop-dusting using a high-power 100W laser for paediatric stone patients.

Material and methods

Outcomes from a prospective stone database were reviewed over a period of 30 months from February 2016–July 2018. All paediatric patients (≤16 years) treated with dusting and pop-dusting were included in our study. Dusting and pop-dusting were performed using Ho:YAG laser with the energy setting ranges of 0.2–0.5 J and 0.5–0.7 J respectively with a frequency of 20–50 Hz.

Results

Twelve patients underwent URS and treatment using this method with mean age of 6.5 years and a male:female ratio of 7:5. The mean and cumulative single stone size was 7.1 mm (3–10 mm) and 11.9 mm (6–40 mm) respectively with half of all patients having multiple stones. Eleven patients were stone free on follow-up with no intra or post-operative complications noted.

Conclusions

Pop-dusting using holmium laser is a new hybrid technique that allows for more efficient dust formation even for hard stones. This is the first clinical study demonstrating the safety and efficacy of this technique in paediatric patients. It is likely there will be wider adoption of these new laser techniques for stone treatment in the paediatric age group.

The laser of the future: reality and expectations about the new thulium fiber laser-a systematic review

The Holmium:yttrium-aluminum-garnet (Ho:YAG) laser has been the gold-standard for laser lithotripsy over the last 20 years. However, recent reports about a new prototype thulium fiber laser (TFL) lithotripter have revealed impressive levels of performance. We therefore decided to systematically review the reality and expectations for this new TFL technology. This review was registered in the PROSPERO registry (CRD42019128695). A PubMed search was performed for papers including specific terms relevant to this systematic review published between the years 2015 and 2019, including already accepted but not yet published papers. Additionally, the medical sections of ScienceDirect, Wiley, SpringerLink, Mary Ann Liebert publishers, and Google Scholar were also searched for peer-reviewed abstract presentations. All relevant studies and data identified in the bibliographic search were selected, categorized, and summarized. The authors adhered to PRISMA guidelines for this review. The TFL emits laser radiation at a wavelength of 1,940 nm, and has an optical penetration depth in water about four-times shorter than the Ho:YAG laser. This results in four-times lower stone ablation thresholds, as well as lower tissue ablation thresholds. As the TFL uses electronically-modulated laser diodes, it offers the most comprehensive and flexible range of laser parameters among laser lithotripters, with pulse frequencies up to 2,200 Hz, very low to very high pulse energies (0.005-6 J), short to very long-pulse durations (200 µs up to 12 ms), and a total power level up to 55 W. The stone ablation efficiency is up to four-times that of the Ho:YAG laser for similar laser parameters, with associated implications for speed and operating time. When using dusting settings, the TFL outperforms the Ho:YAG laser in dust quantity and quality, producing much finer particles. Retropulsion is also significantly reduced and sometimes even absent with the TFL. The TFL can use small laser fibers (as small as 50 µm core), with resulting advantages in irrigation, scope deflection, retropulsion reduction, and (in)direct effects on accessibility, visibility, efficiency, and surgical time, as well as offering future miniaturization possibilities. Similar to the Ho:YAG laser, the TFL can also be used for soft tissue applications such as prostate enucleation (ThuFLEP). The TFL machine itself is seven times smaller and eight times lighter than a high-power Ho:YAG laser system, and consumes nine times less energy. Maintenance is expected to be very low due to the durability of its components. The safety profile is also better in many aspects, i.e., for patients, instruments, and surgeons. The advantages of the TFL over the Ho:YAG laser are simply too extensive to be ignored. The TFL appears to be a real alternative to the Ho:YAG laser and become a true game-changer in laser lithotripsy. Due to its novelty, further studies are needed to broaden our understanding of the TFL, and comprehend the full implications and benefits of this new technology, as well its limitations.