Laser Ablation Efficiency, Laser Ablation Speed, and Laser Energy Consumption During Lithotripsy: What Are They and How Are They Defined? A Systematic Review and Proposal for a Standardized Terminology

Innovative use of the new pulsed-thulium: YAG laser for ureteroscopic lithotripsy: can the "kidney stone calculator" predict lithotripsy duration?

To assess the accuracy of Kidney Stone Calculator(KSC), a software designed for surgical planning, in predicting the duration of lithotripsy during flexible ureteroscopy(FURS) when using the novel pulsed-Thulium: YAG(p-Tm: YAG) laser. From February to August 2023, a single-center prospective study was conducted, including patients with kidney or ureteral stones through non-contrast computed tomography(NCCT), who underwent FURS with p-Tm: YAG laser lithotripsy. KSC used three-dimensional segmentation of the stones from NCCT images, along with an interactive user interface for laser settings, to estimate the stone volume(SV) and the lithotripsy duration(LD). The correlation between the estimated(esLD) and effective(efLD) lithotripsy duration was evaluated. A multiple linear regression analysis was conducted to identify preoperative and intraoperative factors affecting discrepancies between esLD and efLD. Twenty-eight patients were included with a median age of 55(48-74) years and 71% of men. Stone were located in the renal cavities(71%), ureter(21%) or both locations(8%). Median maximum stone diameter(MSD) and SV were respectively 14(11-30)mm and 1239(294, 2000)mm3. Nine patients had a SV equal to or greater than 2000mm3. EsLD and efLD did not differ(28 vs. 32 min, p = 0.8892), and were highly and positively correlated(r = + 0.90,p-value = < 0.001). Multivariate analysis indicated that the difference between estimated and effective lithotripsy were correlated with the stone volume(> 2000mm3), the use of ureteral access sheath and for struvite stones. "Kidney Stone Calculator" can accurately estimate LD during FURS with the p-Tm: YAG laser. Variables such as stone volumes over 2000mm3 and stone composition could be integrated the estimation. KSC is the only software that estimates LD with Holmium: YAG, Thulium Fiber and p-Tm: YAG lasers.

Harnessing magnetism: evaluation of safety, tolerance and feasibility of magnetic kidney stone retrieval in vivo in porcine models

The primary objective of urolithiasis therapy is complete stone removal and highest stone-clearance rates possible to minimize recurrence. A novel approach that employs a magnetic suspension and a magnetic probe for the passive collection and removal of small residual fragments was developed. This study assessed the feasibility of this system in porcine models. Five female domestic pigs underwent retrograde intrarenal surgery under general anaesthesia to assess the new magnetic system. Pre-analysed human calculi were endoscopically inserted and comminuted using lithotripsy. The magnetic suspension was applied, and the magnetic-stone fragment complex was extracted. After nephrectomy, independent blinded pathologists evaluated all the kidneys. Safety and tolerance assessments revealed no adverse events (i.e. no complications on the Clavien-Dindo scale > 1) or complications associated with treatment. This study revealed superficial urothelial damage in all animals, characterized by desquamation and inflammation, caused primarily by the insertion of access sheaths and laser lithotripsy. Residual magnetic particles were observed in the renal pelvis but did not show signs of toxicity even though this study is limited to the acute treatment. No pathological indicators were observed in the hemogram and urinalysis. Overall, the treatment did not cause any significant pathological changes. Preclinical in vivo evaluation of magnetic extraction of small rest fragments in porcine kidneys presents a promising, atraumatic approach for fragments removal. It demonstrated safety, tolerance, and feasibility that warrants clinical investigation. This method has the potential to increase stone-clearance rates with shorter extraction times, offering a possibility for addressing the challenge of urolithiasis in clinical practice.

Thulium fiber laser versus pulsed Thulium:YAG for laser lithotripsy during flexible ureteroscopy

To compare the pulsed-Thulium: YAG(p-Tm: YAG) and Thulium Fiber(TFL) lasers in terms of efficiency and safety profiles during flexible ureteroscopy(fURS) and endocorporeal laser lithotripsy(ELL). A prospective single-center open-label comparative study included consecutive patients with ureteral and renal stones who underwent fURS using Thulio(p-Tm: YAG, Dornier©,Germany) or TFL Drive(TFL, Coloplast©,Danemark), with 270 μm and 150/200μm laser fibers(LF), respectively. fURS were performed by a single operator in each group. Demographics, stone size, stone density, laser-on time(LOT) and laser settings were recorded. Ablation speed(mm3/s), energy consumption(J/mm3) values for each procedure were also assessed. Stone-free rate(SFR, <3 mm fragments) and zero fragment rate(ZFR) on non-contrast computed tomography within 3 months postoperatively were also recorded. 36 and 39 patients were included in p-Tm: YAG and TFL group, respectively. Groups presented similar demographics but for high blood pressure(53vs23%,p = 0,005), anatomical abnormalities(8vs33%,p = 0,03), lower pole(8vs26%,p = 0,04) and pelvic stones(25vs13%,p = 0,04) for p-Tm: YAG and TFL, respectively. The median stone maximum diameter was higher in the p-Tm: YAG group(17.3vs13.8 mm, p = 0,001) but stone volume was similar among groups(1514vs1347mm3,p = 0,6). Laser settings were similar among groups(0,6-15 Hz,10-12 W). Shorter LOT(< 0,001) and lower UAS insertion(0,01) rates were reported for TFL compared to p-Tm: YAG. The median J/mm3 was similar(14vs17,p = 0,2) but p-Tm: YAG presented higher ablation speed(0,91vs0,73mm3/s, p = 0,04). SFR were similar among groups(75vs77%,p = 0,8) but ZFR was higher in TFL group(39vs64%,p = 0,008). No difference in complications was reported. Both p-Tm: YAG and TFL are safe and effective for ELL during fURS. SFR were similar between TFL and p-Tm: YAG but the latter presented lower ZFR, traducing its lower ability to dust. Using 200 μm laser fibers with p-Tm: YAG could nuance these findings.

Optimal stone density for ablation lithotripsy with vapor tunnel Ho:YAG pulse modality

INTRODUCTION

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. There are studies that have shown acceptable ablation lithotripsy efficiency. Nevertheless, there are no in-vivo studies that have compared the VT performance according to the stone density.

METHODS

A retrospective study of 152 patients who underwent RIRS using VT Ho:YAG laser was performed. We divided the patients according to the stone density (Group 1: < 1000UH vs. Group 2: > 1000UH). We assessed the lithotripsy efficiency (mm3/JJ) and the laser-energy consumption (JJ/mm3). The stone-free rate (SFR) was defined as the absence of stone fragments in a non-contrast abdominal computed tomography 4 weeks after the procedure.

RESULTS

Ninety three patients were included in Group 1 and 59 in Group 2. Body mass index was higher in Group 1 and the median stone volume was higher in Group 2 (846 vs. 672 mm3, p = 0.03). Total energy used (11.9 vs. 24 kj, p < 0.001), the laser emission time (19 vs. 30 min, p < 0.001), and the total operative time (60 vs. 85 min, p < 0.001) were lower in the Group 1. SFR was higher in Group 1 (96.7% vs. 57.6%, p < 0.001) with a global SFR of 81.6%. The ablation lithotripsy efficiency was higher in Group 1 (0.053 mm3/JJ vs. 0.035 mm3/JJ, p < 0.001).

CONCLUSIONS

VT Ho:YAG was associated with decreased laser time, operative time and laser-energy consumption in Group 1 than Group 2. Similarly, VT Ho:YAG increased lithotripsy efficiency and the SFR compared to hard stones with the same laser settings and pulse modality.

Multicenter outcome analysis of different sheath sizes for Flexible and Navigable Suction ureteral access sheath (FANS) ureteroscopy: an EAU Endourology collaboration with the global FANS study group

Flexible and navigable suction ureteral access sheath (FANS) is a potential game changer in flexible ureteroscopy (FURS). The influence of sheath size on outcomes needs research. The primary aim was to analyze 30-day single stage stone free status (SFS), zero fragment rate (ZFR) and complications when using 10/12Fr sheaths vis a vis other sheath sizes. The global FANS research group published the 30-day outcomes in patients who underwent FANS and reasoned this can be a potential game changer. We included 295 patients from this anonymized dataset with division into two groups: Group 1 (Smaller sheath) - 10/12Fr FANS, and Group 2 (Larger sheath) - 11/13Fr or 12/14Fr sheaths. Stone volume was similar between both groups (median 1320 mm3, p = 0.88). Ureteroscopy and total operative time was longer in the smaller sheath group (35 vs. 32 min, p = 0.02 and 50 vs. 45 min, p = 0.001, respectively). While 30-day computed tomography SFS (100% stone free or single residual fragment ≤ 2 mm) were not significantly different (96% vs. 95%, p > 0.99), ZFR (100% stone-free) was better with smaller sheaths (68% vs. 53%, p = 0.02). There was no difference in postoperative complication rates, and no sepsis in both groups. Urologists should consider individualizing appropriate sheath size in normal adult kidneys. Sheath size did not affect complication rates, risk of perioperative injury to the pelvicalyceal system or ureteric injury, but smaller FANS sheaths had similar high SFS. The ZFR with smaller sheaths was better, but this needs to be validated. These smaller sheath outcomes need to be balanced with longer ureteroscopy time, operative time, reach to the lower pole, ease of suction and visibility during lithotripsy. Large volume studies in different types of pelvicalyceal anatomy can determine if indeed smaller FANS is the best choice in FURS.

Flexible Ureteroscopic Lithotripsy with the Pulsed Thulium:Yttrium Aluminum Garnet Laser Thulio: Preliminary Results from a Prospective Study

Background and objective

Recently, the new pulsed thulium:yttrium aluminum garnet (p-Tm:YAG) laser technology has been introduced in endourology for lithotripsy. The aim of this study was to assess and validate the clinical laser performance and safety profile of p-Tm:YAG laser in a series of patients with renal and ureteral stones who underwent flexible ureteroscopy (fURS).

Methods

Prospective data were collected for patients who underwent fURS with the p-Tm:YAG laser Thulio (Dornier MedTech Systems GmbH, Wessling, Germany) at our institution by using two different laser fiber core diameters (270 and 200 μm). The primary endpoint of the study was stone-free rate (SFR), and the secondary endpoints were Clavien-Dindo complications grade ≥1 and the comparison between laser fibers of different diameters in all the parameters analyzed. Descriptive statistics relied on medians and interquartile ranges for continuous covariates, and on frequencies and percentages for categorical covariates. After stratification according to fiber types, differences between groups were tested with Wilcoxon and chi-square tests as appropriate. All the analyses and graphics were performed using R software (version 4.2.2).

Key findings and limitations

The SFR was 82% at 1-mo follow-up. In six out of 50 procedures (12%), Clavien-Dindo grade I-II complications were recorded. There were no differences regarding all the laser parameters considered between patients who were treated with 270 or 200 μm laser fibers (p > 0.05). Limitations of the study include small sample size in a single center and the lack of comparative groups.

Conclusions and clinical implications

In this prospective study of 50 patients who underwent fURS for ureteral and renal stones, the p-Tm:YAG laser Thulio was both effective and safe in a short-term follow-up. More prospective randomized studies in larger populations using different laser sources are required to confirm the clinical laser performance and safety of p-Tm:YAG laser for urinary stones treatment.

Patient summary

In this report, we looked at the outcomes for the pulsed thulium:yttrium aluminum garnet laser Dornier Thulio in patients who underwent flexible ureteroscopy for ureteral and renal stones. We found that this new laser technology is effective and safe, representing a good alternative to the other laser machines available for stone lithotripsy. We need more studies with larger populations to establish the superiority of this laser technology over the others.

Rethinking Stone-free Rates and Surgical Outcomes in Endourology: A Point of View from PEARLS Members

There is a lack of consensus on definitions for the success of endourological stone treatments. The zero-fragment rate (residual fragments [RFs] <1 mm) is now considered more accurate than the stone-free rate (RFs ≤4 mm). As stone volume may be adopted as the recommended method for preoperative estimation of the stone burden, the volumetric stone-free rate may be superior to standard linear RF measurements in defining success.

Steady-state versus burst lasing techniques for thulium fiber laser

OBJECTIVE

To evaluate the stone ablation rate and direct thermal damage from thulium fiber laser (TFL) lithotripsy using continuous (C) and burst (B) lasing techniques on an in vitro ureteral model.

METHODS

The TFL Drive (Coloplast, Humlebaek, Denmark) was used in an in vitro saline-submerged ureteral model. Ten participants, including five junior and five experienced urologists, conducted the experimental setup with 7 different settings comparing two lasing techniques: steady-state lasing (0.5 J/10 Hz = 5W for 300 s and 0.5 J/20 Hz = 10W for 150 s) and burst, intermittent 5 s on/off lasing (0.5 J/20 Hz, 0.5 J/30 Hz, 0.5 J/60 Hz, 0.1 J/200 Hz, and 0.05 J/400 Hz) with a target cumulative energy of 1500 J using cubic 125 mm3 phantom BegoStonesTM. Ureteral damage was graded 1-3 based on the severity of burns and holes observed on the surface of the ureteral model.

RESULTS

The were no significant differences in stone ablation mass neither between C and B lasing techniques, nor between expertise levels. At C lasing technique had only mild ureteral lesions with no significant differences between expertise levels (p: 0.97) or laser settings (p: 0.71). At B lasing technique, different types of thermal lesions were found with no expertise (p: 0.11) or setting (p: 0.83) differences. However, B laser setting had higher grade direct thermal lesions than C (p: 0.048).

CONCLUSION

Regarding efficacy, C and B lasing techniques achieve comparable stone ablation rates. Safety-wise, B lasing mode showed higher grade of direct thermal lesions. These results should be further investigated to verify which of the lasing mode is the safest in vivo. Until then and unless proven otherwise, a C mode with low frequency should be recommended to avoid ureteral wall lesions.