Temperature Measurements During Flexible Ureteroscopic Laser Lithotripsy: A Prospective Clinical Trial

Objective: The primary aim of the study was to explore intrarenal temperatures (IRTs) during flexible ureteroscopic laser lithotripsy (FURSL). The secondary aim was to investigate the correlation between temperatures and renal pelvis anteroposterior diameter (APD). Materials and Methods: From February 2023 to June 2023, 10 patients with an indwelling nephrostomy tube (NT) undergoing FURSL were enrolled in the study. Sheathless FURSL was performed using gravitational irrigation (23°C) at 60 cm. A sterile K-type thermocouple was inserted through the NT. Temperatures were recorded for 120 seconds with continuous laser activation and for another 60 seconds after deactivation. Thulium fiber laser delivered energy using a 150 μm fiber and incremental power settings of 5, 10, 20, and 30 W. The laser was deactivated whenever the IRT reached 43°C. Results: IRT correlated directly to power settings. Each time the power settings were increased, the temperature rose significantly. The increase in average peak temperature was 2.6°C between 5 and 10 W (p < 0.001), 3.4°C between 10 and 20 W (p < 0.001), and 2.5°C between 20 and 30 W (p < 0.001). Temperatures reached 43°C in three patients applying 20 W and in eight patients applying 30 W. The shortest activation-time until threshold was 12 and 28 seconds with 30 and 20 W settings, respectively. When reaching 43°C, temperatures remained above this threshold for an additional 29 seconds on average. There was a significant correlation between IRT and renal APD. For example, when 10 W was applied in the setting of APD ≤20 mm, the recorded temperature was on average 2.3°C higher compared with APD >20 mm, with the same power settings applied, p < 0.001. Conclusion: During FURSL, IRT correlates directly with power settings and is inversely correlated with renal pelvic APD. Using a sheathless approach, power settings ≥20 W should arguably be avoided, especially in the context of a nondilated renal pelvis. ClinicalTrials: The study was registered on ClinicalTrials.gov (NCT05677425).

Comparative Analyses and Ablation Efficiency of Thulium Fiber Laser by Stone Composition

PURPOSE

There are limited data on ablation effects of thulium fiber laser (TFL) settings with varying stone composition. Similarly, little is known surrounding the photothermal effects of TFL lithotripsy regarding the chemical and structural changes after visible char formation. We aim to understand the TFL's ablative efficiency across various stone types and laser settings, while simultaneously investigating the photothermal effects of TFL lithotripsy.

MATERIALS AND METHODS

Human specimens of calcium oxalate monohydrate, calcium oxalate dihydrate, uric acid, struvite, cystine, carbonate apatite, and brushite stones were ablated using 13 prespecified settings with the Coloplast TFL Drive. Pre- and postablation mass, ablation time, and total energy were recorded. Qualitative ablative observations were recorded at 1-minute intervals with photographs and gross description. Samples were analyzed with Fourier-transform infrared spectroscopy pre- and postablation and electron microscopy postablation to assess the photothermal effects of TFL.

RESULTS

Across all settings and stone types, 0.05 J × 1000 Hz was the best numerically efficient ablation setting. When selected for more clinically relevant laser settings (ie, 10-20 W), 0.2 J × 100 Hz, short pulse was the most numerically efficient setting for calcium oxalate dihydrate, cystine, and struvite stones. Calcium oxalate monohydrate ablated with the best numerical efficiency at 0.4 J × 40 Hz, short pulse. Uric acid and carbonate apatite stones ablated with the best numerical efficiency at 0.3 J × 60 Hz, short pulse. Brushite stones ablated with the best numerical efficiency at 0.5 J × 30 Hz, short pulse. Pulse duration impacted ablation effectiveness greatly with 6/8 (75%) of inadequate ablations occurring in medium or long pulse settings. The average percent of mass lost during ablation was 57%; cystine stones averaged the highest percent mass lost at 71%. Charring was observed in 36/91 (40%) specimens. Charring was most often seen in uric acid, cystine, and brushite stones across all laser settings. Electron microscopy of char demonstrated a porous melting effect different to that of brittle fracture. Fourier-transform infrared spectroscopy of brushite char demonstrated a chemical composition change to amorphous calcium phosphate.

CONCLUSIONS

We describe the optimal ablation settings based on stone composition, which may guide urologists towards more stone-specific care when using thulium laser for treating renal stones (lower energy settings would be safer for ureteral stones). For patients with unknown stone composition, lasers can be preset to target common stone types or adjusted based on visual cues. We recommend using short pulse for all TFL lithotripsy of calculi and altering the settings based on visual cues and efficiency to minimize the charring, an effect which can make the stone refractory to further dusting and fragmentation.

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.

Prospective Randomized Controlled Trial to Compare Dusting vs Fragmentation Using Thulium Fiber Laser in Retrograde Intrarenal Surgery

Objective: To compare the dusting vs fragmentation modes with thulium fiber laser (TFL) in retrograde intrarenal surgery (RIRS) for upper tract stones using the same fixed low-power settings in both the arms. The primary objective was to compare the stone-free rate (SFR) and secondary objectives were to compare mean operating times, hospital stay duration, complication rates, need for secondary procedures, and laser efficacy. Materials and Methods: A prospective randomized trial, with patients having proximal ureteral or renal stones of 10-20 mm and planned for RIRS was done at a single institute. A total of 60 consecutively admitted patients with signed consent were included for randomization with 30 patients in each arm of dusting and fragmentation modes. Results: Median age in dusting and fragmentation arms of 41.5 and 45.5 years, median stone size of 10.45 and 12.25 mm, median stone volume of 351.6 and 490.7 mm3, and median stone density of 1263.5 HU in both arms with comparable hospital stay of median of 2 days in both arms. Lasing time was significantly lesser in the fragmentation group (20.5 minutes; interquartile range [IQR] 15.12-31.62) than in the dusting group (34.25 minutes, IQR 26.62-38.62, p < 0.001). Higher ablation speed for fragmentation mode (0.405 mm3/sec, IQR 0.337-0.635) than for dusting mode (0.17 mm3/sec, IQR 0.135-0.325, p < 0.001). SFRs and complication rates were comparable in both the arms. Conclusion: TFL in fragmentation mode has shorter lasing times and better laser efficacy than dusting mode with comparable minimal complications, SFRs, and hospital stay duration. Clinical Trial Registration number: CTRI050827.

In Pursuit of the Optimal Dusting Settings with the Thulium Fiber Laser: An In Vitro Assessment

Objective: Low energy and high frequency settings are used in stone dusting for holmium lasers. Such settings may not be optimal for thulium fiber laser (TFL). With the seemingly endless combination of settings, we aim to provide guidance to the practicing urologists and assess the efficiency of the TFL platform in an automated in vitro "dusting model." Materials/Methods: Three experimental setups were designed to investigate stone dusting produced by an IPG Photonics TLR-50 W TFL system using 200 μm fiber and soft BegoStone phantoms. The most popular 10 and 20 W dusting settings among endourologist familiar with TFL were evaluated. We directly compared short pulse (SP) vs long pulse (LP) mode using various combinations of pulse energy (Ep) and pulse frequency (F). Thereafter, we tested the 10 and 20 W settings and compared them among each other to elucidate the most efficient settings at each power. Treatments were performed under the same total laser energy delivered to the stone at four different standoff distances (SDs) with a clinically relevant scanning speed of either 1 or 2 mm/sec. Ablation volumes were quantified by optical coherence tomography to assess stone dusting efficiency. Fragment size after ablation at different pulse energies was evaluated by sieving and evaluating under a microscope after treatment. Results: Overall, SP provided greater ablation volume when compared with LP. Our dusting efficiency model demonstrated that the maximum stone ablation was achieved at the combination of high energy/low frequency settings (p < 0.005) and at a SD of 0.2 mm. At all tested pulse energies, no stone phantoms were broken into fragments >1 mm. Conclusions: During stone dusting with TFL, SP offers superior ablation to LP settings. Optimal dusting at clinically relevant scanning speeds of 1 and 2 mm/sec occurs at high energy/low frequency settings. Thulium lithotripsy with high Ep does not result in increased fragment size.

Ureteroscopic lithotripsy by thulium fiber laser versus holmium laser: A single-center prospective randomized study

Objective

Laser lithotripsy has been the standard of care for lower and mid-ureteric calculi. Thulium fiber laser (TFL) is a new introduction to this field, which has been extensively studied for retrograde intrarenal surgery. We have done a prospective randomized study of ureteroscopic lithotripsy between TFL and holmium: Yttrium-aluminum-garnet (HO: YAG) laser to know the efficacy of stone fragmentation, stone-free rate, and complications.

Methodology

A prospective randomized study was done in our hospital from March 2021 to May 2022 on patients planned for ureteroscopic laser lithotripsy. Patients with distal and mid-ureteral stones from 4 mm to 15 mm were included. The laser was used to fragment the stone. All the stones were fragmented from the center to periphery. The setting used was up to 10 W (6-10 Hz, 1J) for TFL and up to 10 W for HO: YAG (5-10 Hz, 0.5-1J). Once the stones were fragmented, they were retrieved until complete visual clearance. Demographic data and stone parameters such as stone size, volume, density, laterality, laser usage time, total operative time, and total energy used were recorded. Operative time, lasering time, retropulsion rate, ablation speed, and visibility score were recorded.

Results

Each group had 90 randomized patients. Both the groups had similar kinds of patient and stone profiles. The mean operating time was 18.5 ± 1.5 min (95% confidence interval [CI] 16.2-25.6) in the TFL group, which was shorter than the holmium group 31.6 ± 1.2 min (95% CI 18.4-38.5), and it was statistically significant (P = 0.024,). Lasering time was also statistically significant with less lasering time with TFL group 7.4 ± 1.8 min (95% CI 5.2-10.3) versus holmium group 14.8 ± 1.5 min (95% CI 12.3-18.4) (P = 0.011). Laser efficacy and ablation speed were better in the TFL group compared to the HO: YAG group and were statistically significant. The visual score was better in HO: YAG group compared to the TFL group.

Conclusion

TFL is more efficacious and faster than Holmium: Yag laser. Complications were similar between the groups. Stone-free rate was also similar between both the groups.

[Comparative study of the efficacy and safety of a new generation of thulium fiber lasers for ureteroscopy and lithotripsy]

INTRODUCTION

The development and implementation in clinical practice of a 3rd generation thulium fiber laser with the possibility of computer control (modulation) of the shape, amplitude and pulse repetition rate opens up new possibilities for thulium fiber laser lithotripsy.

AIM

To carry out a comparative study of the efficacy and safety of thulium fiber laser lithotripsy using a of the 2nd (FiberLase U3) and 3rd generation devices (FiberLase U-MAX).

MATERIALS AND METHODS

A total of 218 patients with solitary ureteral stones, who underwent to ureteroscopy with lithotripsy using 2nd and 3rd generation thulium fiber lasers (IRE-Polus, Russia) from January 2020 to May 2022 with the same peak power (500 W), laser settings of 1 joule, 10 Hz and with a laser fiber diameter of 365 m, were included in the prospective study. For lithotripsy using FiberLase U-MAX laser a new original modulated pulse, which was found and optimized in a preclinical study, was used. Depending on the laser, the patients were divided into 2 groups. In 111 patients, stone fragmentation was performed on FiberLase U3 (2nd generation), while 107 patients were undergone to lithotripsy on a new laser device FiberLase U-MAX (3rd generation). Stone size ranged from 6 mm to 28 mm (11+/-4 mm). The duration of procedure and lithotripsy, the quality of the endoscopic picture during fragmentation (from 0 to 3 points, 0-bad, 3-excellent), the frequency of retrograde migration of stones, as well as damage to ureteral mucosa (of 1-3 degrees) were evaluated.

RESULTS

The time of lithotripsy was significantly lower in the group 2 than in the group 1 (12.3+/-4.6 vs. 24.7+/-6.2 min; p<0.05). The average quality of the endoscopic picture was significantly better in the group 2 (2.5+/-0.4 vs. 1.8+/-0.2 points; p<0.05). Clinically significant retrograde migration of stone or its fragments (the need for additional ESWL, flexible ureteroscopy) was noted in 16% vs. 8% of patients in group 1 and 2, respectively (p<0.05). Damage to ureteral mucosa of the 1st and 2nd degree due to laser exposure in the group 1 was noted in 24 (22%) and 8 (7%) cases, compared to 21 (20%) and 7 (7%) cases in group 2, respectively. Stone-free state was 84% in group 1 and 92% in group 2.

CONCLUSION

Modulation of the laser pulse shape allowed to improve endoscopic visibility, increase the speed of lithotripsy, reduce the frequency of retrograde stone migration without increasing the trauma to ureteral mucosa.

Incidence of Ureteric strictures Following Ureteroscopic Laser Lithotripsy: Holmium:YAG Versus Thulium Fiber Laser

OBJECTIVE

We aimed to compare the incidence of ureteric strictures between holmium:yttrium aluminum garnet and thulium fiber laser following ureteroscopic laser lithotripsy. In the present era of miniaturization of endourologic armamentarium and better optics, how safe are lasers to fire inside ureter?

MATERIALS AND METHODS

It is a prospective comparative study over a period of 2 years that included patients who underwent ureteroscopic laser lithotripsy for ureteric stones. Patients were randomly divided into 2 groups: group A underwent holmium:yttrium aluminum garnet laser lithotripsy and group B underwent thulium fiber laser lithotripsy.

RESULTS

A total of 478 patients were analyzed after excluding patients not willing to participate and patients lost to follow-up. Two hundred forty patients underwent holmium:yttrium aluminum garnet laser lithotripsy (group A) and 238 patients underwent thulium fiber laser lithotripsy (group B). The demographic data of 2 groups were comparable. The mean age of patients in group A and group B was 36.5 ± 12.52 years and 38.62 ± 10.71 years, respectively. The mean operative time in group A and group B was 47 ± 15 and 36 ± 13 minutes, respectively, while the mean laser time in group A and group B was 13.5 ± 45 minutes and 9.25 ± 3.2 minutes, respectively. Four (1.67%) patients in group A and 11 (4.62%) patients in group B developed ureteric strictures during follow-up, and the difference was statistically significant (P <.001). The mean length of stricture was 2.67 ± 1.27 cm in group A and 4.42 ± 2.2 cm in group B, and the difference was statistically significant.

CONCLUSION

Thulium fiber laser, projected as safe laser previously, has a higher incidence of ureteric strictures compared to holmium:yttrium aluminum garnet laser when used for ureteroscopic laser lithotripsy.

14F Super-Mini Percutaneous Cystolitholapaxy: A Novel Technique in the Treatment of Bladder Stones

Introduction: This single-center experience describes the indications, novel technique, and outcomes of performing 14F super-mini percutaneous cystolitholapaxy (14F-SMPCCL). Materials and Methods: Cases between 2019 and 2022 were retrospectively identified with surgical outcomes recorded. Using percutaneous access to the bladder, an endoscope was inserted through the ClearPetra 14F super-mini sheath and laser lithotripsy completed with stone fragments suctioned out. Results: Sixteen cases were included in the study and all patients were adults. Average conglomerate stone size was 28.1 mm (range = 10-50 mm). Average operative time was 60.0 minutes (range = 23-110 minutes). Visual stone-free rate was 91.7%, radiologic stone-free rate was 81.3%, and average postoperative length of stay was 1 day. One patient developed urosepsis postoperatively and there were no other complications. Conclusion: The novel technique of 14F-SMPCCL is safe and feasible for treating large burdens of bladder stones with a conglomerate size of ∼2.5 to 5 cm. Active suction allows for efficient removal of stone fragments.

Laser Efficiency and Laser Safety: Holmium YAG vs. Thulium Fiber Laser

(1) Objective: To support the efficacy and safety of a range of thulium fiber laser (TFL) pre-set parameters for laser lithotripsy: the efficiency is compared against the Holmium:YAG (Ho:YAG) laser in the hands of juniors and experienced urologists using an in vitro ureteral model; the ureteral damage of both lasers is evaluated in an in vivo porcine model. (2) Materials and Methods: Ho:YAG laser technology and TFL technology, with a 200 µm core-diameter laser fibers in an in vitro saline ureteral model were used. Each participant performed 12 laser sessions. Each session included a 3-min lasering of stone phantoms (Begostone) with each laser technology in six different pre-settings retained from the Coloplast TFL Drive user interface pre-settings, for stone dusting: 0.5 J/10 Hz, 0.5 J/20 Hz, 0.7 J/10 Hz, 0.7 J/20 Hz, 1 J/12 Hz and 1 J/20 Hz. Both lasers were also used in three in vivo porcine models, lasering up to 20 W and 12 W in the renal pelvis and the ureter, respectively. Temperature was continuously recorded. After 3 weeks, a second look was done to verify the integrity of the ureters and kidney and an anatomopathological analysis was performed. (3) Results: Regarding laser lithotripsy efficiency, after 3 min of continuous lasering, the overall ablation rate (AR) percentage was 27% greater with the TFL technology (p < 0.0001). The energy per ablated mass [J/mg] was 24% lower when using the TFL (p < 0.0001). While junior urologists performed worse than seniors in all tests, they performed better when using the TFL than Ho:YAG technology (36% more AR and 36% fewer J/mg). In the in vivo porcine model, no urothelial damage was observed for both laser technologies, neither endoscopically during lasering, three weeks later, nor in the pathological test. (4) Conclusions: By using Coloplast TFL Drive GUI pre-set, TFL lithotripsy efficiency is higher than Ho:YAG laser, even in unexperienced hands. Concerning urothelial damage, both laser technologies with low power present no lesions.

Temperature profiles during ureteroscopy with thulium fiber laser and holmium:YAG laser: Findings from a pre-clinical study

OBJECTIVE

The aim of this study was to investigate temperature profiles in both the renal pelvis and parenchyma during Thulium Fiber Laser (TFL) and Holmium:yttrium-aluminium-garnet (Ho:YAG) laser activation in an ex-vivo porcine model.

METHODS

Three porcine kidneys with intact renal pelvis and proximal ureters were used in the study. A temperature sensor was inserted through a nephrostomy tube into the renal pelvis and a second sensor was inserted directly into the renal parenchyma. Temperatures were recorded during continuous laser activation for 180 s, and for an additional 60 s after deactivation. TFL (150 μm and 200 μm) and Ho:YAG (270 μm) laser delivered power at settings of 2.4 W, 8 W, 20 W and 30 W.

RESULTS

Intrapelvic temperatures correlated directly to power settings. Higher power produced higher temperatures. For example, using a 150 μm fiber at 2.4 W resulted in a 2.6 °C rise from baseline (p = 0.008), whereas using the same fiber at 20 W produced a rise in temperature of 19.9 °C (p = 0.02). Larger laser fibers caused significantly higher temperatures compared to smaller fibers using equivalent power settings, e.g. mean temperature at 20 W using 150 μm was 39.6 °C compared to 44.9 °C using 200 μm, p < 0.001. There was a significant increase in parenchymal temperatures when applying 20 W and 30 W of laser power with the two larger fibers.

CONCLUSION

In this ex-vivo study, renal temperatures correlated directly to power settings. Higher power produced higher temperatures. Furthermore, larger laser fibers caused higher temperatures. These findings could help guide selection of safe power settings for ureteroscopic lithotripsy, but future clinical studies are needed for confirmation.

Assessment of Factors Involved in Laser Fiber Degradation with Thulium Fiber Laser

Objectives: To assess the effect of various factors on laser fiber tip degradation with the thulium fiber laser (Tm-fiber): fiber stripping, adjustable laser settings (energy, frequency, peak power), and stone density. Methods: Two hundred seventy-three micrometer fibers were used with a 50W Tm-fiber. First, we assessed the evolution of power transmission with stripped and unstripped fibers submerged in saline. The laser was continuously activated for 5 minutes. The influence of each laser parameter (energy, frequency, and peak power) on fiber degradation was assessed by loss of power transmission and reduction of tip length. Second, we assessed the evolution of power transmission after 150 seconds of lithotripsy in a quasicontact mode against soft and hard BegoStones. The influence of lithotripsy with different laser settings on fiber degradation was assessed by loss of power transmission. Results: Power transmission was close to 100% with stripped fibers, while a power gain appeared for unstripped fibers after 5 minutes of laser emission. Thus, only stripped laser fibers were used during the second series of experiments. Regardless of laser settings, there was a constant loss of measured power transmission after lithotripsy with a significant difference between soft and hard stones, p < 0.0001. Power transmission was 67% and 78% against hard and soft stones, respectively. While there was no influence of peak power on power output against hard stones, there was a significant one against soft stones. Conclusions: The main determinant of loss of power transmission during lithotripsy in contact mode with Tm-fiber is the stone density. Higher loss of power transmission occurs against hard stones than soft stones. All peak powers may be used against hard stones without a difference, while high peak power appears as an additional factor of power loss against soft stones, but this decrease will not the reach the one obtained with hard stones.

Laser Fiber Displacement Velocity during Tm-Fiber and Ho:YAG Laser Lithotripsy: Introducing the Concept of Optimal Displacement Velocity

BACKGROUND

Endocorporeal laser lithotripsy (EL) during flexible ureteroscopy (URS-f) often uses "dusting" settings with "painting" technique. The displacement velocity of the laser fiber (LF) at the stone surface remains unknown and could improve EL's ablation rates. This in vitro study aimed to define the optimal displacement velocity (ODV) for both holmium:yttrium-aluminium-garnet (Ho:YAG) and thulium fiber laser (Tm-Fiber).

METHODS

A 50W-TFL (IRE Polus^®, Moscow, Russia) and a 30W-MH1-Ho:YAG laser (Rocamed^®, Signes, Provence-Alpes-Côte d'Azur, France), were used with 272 µm-Core-Diameter LF (Sureflex, Boston Scientific^©, San Jose, CA, USA), comparing three TFL modes, "fine dusting" (FD: 0.05-0.15 J/100-600 Hz); "dusting" (D: 0.5 J/30-60 Hz); "fragmentation" (Fr: 1 J/15-30 Hz) and two Ho:YAG modes (D: 0.5 J/20 Hz, Fr: 1 J/15 Hz). An experimental setup consisting of immerged cubes of calcium oxalate monohydrate (COM) stone phantoms (Begostone Plus, Bego^©, Lincoln, RI, USA) was used with a 2 s' laser operation time. LF were in contact with the stones, static or with a displacement of 5, 10 or 20 mm. Experiments were repeated four times. Stones were dried and µ-scanned. Ablation volumes (mm³) were measured by 3D-segmentation.

RESULTS

ODV was higher in dusting compared to fragmentation mode during Ho:YAG lithotripsy (10 mm/s vs. 5 mm/s, respectively). With Tm-Fiber, dusting and fragmentation OVDs were similar (5 mm/s). Tm-Fiber ODV was lower than Ho:YAGs in dusting settings (5 mm/s vs. 10 mm/s, respectively). Without LF displacement, ablation volumes were at least two-fold higher with Tm-Fiber compared to Ho:YAG. Despite the LF-DV, we report a 1.5 to 5-fold higher ablation volume with Tm-Fiber compared to Ho:YAG.

CONCLUSIONS

In dusting mode, the ODV^Tm-Fiber is lower compared to ODV^Ho:YAG, translating to a potential easier Tm-Fiber utilization for "painting" dusting technique. The ODV determinants remain unknown. Dynamic ablation volumes are higher to static ones, regardless of the laser source, settings or LF displacement velocity.

Dusting Efficiency of a Novel Pulsed Thulium:Yttrium Aluminum Garnet Laser vs a Thulium Fiber Laser

Background: Holmium:yttrium aluminum garnet laser (Ho:YAG) is still considered the gold standard in laser lithotripsy. There is a large body of literature comparing the capabilities of Ho:YAG and thulium fiber lasers (TFLs). The novel, pulsed thulium:yttrium aluminum garnet laser (p-Tm:YAG) evaluation model has only been compared with Ho:YAG in terms of its dusting performance to date. It was this study's aim to compare the p-Tm:YAG's dusting efficiency with that of a chopped TFL. Materials and Methods: During the laser ablation procedure, while the laser device was emitting light, the laser fiber was spiraled across the surface of a uniform kidney stone model via software. We relied on the stone model's difference in weight before and after the dusting procedure to assess the dusting efficiency and assessed each laser device's dusting efficiency at various preset laser configurations and laser fiber-motion speeds. We compared both laser devices' laser configurations, which were identical in pulse energy and frequency, while keeping in mind that the pulse duration differed significantly. In addition, we tested each laser device's capability. Results: The average ablated weight across all laser configurations was 0.61 g (standard deviation [SD] = 0.44 g) for p-Tm:YAG and 0.76 g (SD = 0.51 g) for TFL. After statistical analysis, we found no significant difference in ablated weight between the laser devices (U = 1715.5, p-value = 0.11). The maximum permissible frequency configuration for TFL was 1600 Hz, which resulted in the worst overall dusting output. Conclusions: We observed that the p-Tm:YAG's dusting efficiency resembled that of TFL in the identical pulse energy and frequency laser configurations. The ablation efficiency did not seem to be affected by the laser devices' differences in pulse duration. Slower laser fiber-motion speeds resulted in more efficient ablation. When using the maximum preset frequency and power configuration, TFL's dusting efficiency appeared to be inefficient.

Managing Urolithiasis with Thulium Fiber Laser: Updated Real-Life Results-A Systematic Review

Thirty-three years ago, pulsed lasers marked the beginning of a new era in endoscopic lithotripsy, and the one that was highlighted because of its potential was the Holmium: YAG laser, which became and still is the gold standard in endourology. Recently, a new laser technology has been accepted for clinical use in lithotripsy: the thulium fiber laser (TFL), showing appealing characteristics not seen before in several preclinical studies. A review of the literature was performed and all relevant in vitro studies and clinical trials until April 2021 were selected. The search came back with 27 clinical experiences (7 full-text clinical trials and 20 peer-reviewed abstracts) and 33 laboratory studies (18 full-text articles and 15 peer-reviewed abstracts). The clinical experiences confirmed the clinical safety of using the wide parameter range of the TFL. This technology demonstrated the performance at a higher ablation speed, the higher ablation efficiency, and the better dust quality of the TFL, as well as reduced stone retropulsion, thus helping to maintain an optimal visibility. No thermal or radiation damage was found. Given the current evidence, we may be facing the future gold standard laser in endoscopic lithotripsy.

A Systematic Review of Thulium Fiber Laser: Applications and Advantages of Laser Technology in the Field of Urology

Laser technology is widely used in urological surgery, from lithotripsy, prostate surgery to en-bloc resection of tumours. While Holmium:YAG has been widely employed over the last two decades, in recent years, there has been a surge of interest in Thulium Fiber Laser (TFL), which offers theoretical advantages of better water absorption and lower stone ablation thresholds. A systematic review was conducted to assess the evidence from clinical research on TFL's application for lithotripsy and prostate surgery. It identified 357 articles and 8 (1506 patients) were selected, of which 4 clinical studies each investigated TFL enucleation of prostate (ThuFLEP) and TFL lithotripsy. For flexible ureteroscopic lithotripsy (FURSL), stone ablation settings ranged from 0.1-4 J, and 7-300 Hz, mean operative time ranged from 23.4-39.8 minutes and lasing time ranged from 1.2-10 minutes. For stone dusting in percutaneous nephrolithotomy (PCNL), settings of 0.2 J and 125-200 Hz were found to be optimal. For ThuFLEP, all studies showed a significant improvement in IPSS (International Prostate Symptom Score), urinary flow rate (Qmax), quality of life measures, and post-void residual volume, with mean operative time ranging from 67-104.5 minutes. Our review shows that there is limited evidence on the use and clinical outcomes of TFL. ThuFLEP might suggest equivalence to the widely used HoLEP in the available evidence so far. TFL lithotripsy shows promising results but further prospective, randomized trials are required to properly assess its usability, clinical effectiveness and standardisation of the settings for successful adoption of the technology.

Comparison of Holmium:YAG and Thulium Fiber Lasers on the Risk of Laser Fiber Fracture

Objectives: To compare the risk of laser fiber fracture between Ho:YAG laser and Thulium Fiber Laser (TFL) with different laser fiber diameters, laser settings, and fiber bending radii. METHODS: Lengths of 200, 272, and 365 μm single use fibers were used with a 30 W Ho:YAG laser and a 50 W Super Pulsed TFL. Laser fibers of 150 µm length were also tested with the TFL only. Five different increasingly smaller bend radii were tested: 1, 0.9, 0.75, 0.6, and 0.45 cm. A total of 13 different laser settings were tested for the Ho:YAG laser: six fragmentation settings with a short pulse duration, and seven dusting settings with a long pulse duration. A total of 33 different laser settings were tested for the TFL. Three laser settings were common two both lasers: 0.5 J × 12 Hz, 0.8 J × 8 Hz, 2 J × 3 Hz. The laser was activated for 5 min or until fiber fracture. Each measurement was performed ten times. Results: While fiber failures occurred with all fiber diameters with Ho:YAG laser, none were reported with TFL. Identified risk factors of fiber fracture with the Ho:YAG laser were short pulse and high energy for the 365 µm fibers (p = 0.041), but not for the 200 and 272 µm fibers (p = 1 and p = 0.43, respectively). High frequency was not a risk factor of fiber fracture. Fiber diameter also seemed to be a risk factor of fracture. The 200 µm fibers broke more frequently than the 272 and 365 µm ones (p = 0.039). There was a trend for a higher number of fractures with the 365 µm fibers compared to the 272 µm ones, these occurring at a larger bend radius, but this difference was not significant. Conclusion: TFL appears to be a safer laser regarding the risk of fiber fracture than Ho:YAG when used with fibers in a deflected position.

Ablation Efficiency of a Novel Thulium Fiber Laser: An In Vitro Study on Laser Setting and Fiber Usage

Introduction: To investigate the ablation efficiency of super-pulse thulium fiber laser (SPTFL) with different laser settings and fiber usage. Materials and Methods: SPTFL machine was attached with different fibers. Artificial stones were fixed in water, whereas laser fiber was driven on a platform for ablation. Pulse energy, frequency, fiber-moving speed, fiber-to-stone distance, and fiber size were adjusted in each trial. The cross-sectional area of craters on the lateral stone surface was measured for comparison of ablation rate, combined with fiber-moving speed. Results: There was a trend that the ablation rate increased as pulse energy or frequency increased. When pulse energy was set as 0.2 J and frequency was increased from 50 to 150 Hz, the cross-sectional area of the crater was enlarged from 0.21 to 0.37 mm² (p < 0.05); when the frequency was set as 100 Hz and pulse energy was increased from 0.1 to 0.3 J, the crater was enlarged from 0.10 to 0.45 mm² (p < 0.05). Furthermore, energy demonstrated greater impact on ablation rate and the crater was enlarged from 0.20 mm² in the 0.1 J × 300 Hz group to 0.44 mm² in the 0.3 J × 100 Hz group (p < 0.05). Then fiber was set at different moving speeds with the same laser setting; the ablation rate of 3 mm/second group was 3.64 times higher than 0.5 mm/second group (p < 0.05). Ablation diminished as fiber-to-stone distance grew. A 200 μm fiber produced thinner and deeper fissure than 272 and 550 μm fibers, and the ablation rate was the highest for the 200 μm fiber. Conclusion: Pulse energy is a more important factor in influencing ablation efficiency compared with frequency. Closer fiber-to-stone distance, faster fiber movement, and smaller fiber size increase ablation efficiency.

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.

Retrospective Assessment of Endoscopic Enucleation of Prostate Complications: A Single-Center Experience of More Than 1400 Patients

Introduction: Endoscopic enucleation of the prostate (EEP) is a safe method of treating benign prostatic hyperplasia, regardless of prostate volume and type of applied energy. To date, however, there has been no study that examines complication rates with respect to the type of applied energy. This study aims to address this problem by providing a retrospective analysis of >1400 patients who have undergone prostate enucleation. Materials and Methods: We performed a retrospective analysis of all patients undergoing EEP between 2013 and 2018 at a single tertiary institution. This analysis included patients who had undergone one of three forms of EEP: holmium laser enucleation of the prostate (HoLEP), thulium fiber laser enucleation of the prostate (ThuFLEP), or monopolar enucleation of the prostate (MEP). We compared intraoperative and early postoperative complications, as well as complications at 3 and 6 months follow-up. Results: A total of 1413 patients were included in this study; 36% patients underwent HoLEP, 57.5% had ThuFLEP, and 6.5% MEP. The most frequent complication in the early postoperative period was a mild fever (2.76% of the cases). The morcellation was delayed to a separate stage because of intensive hemorrhaging in 1.4% of the cases. Bladder tamponade was found in 1.1% of the cases. We found no correlation between complication rate and either prostate volume or energy source. Stress urinary incontinence was found in 3.9% of patients at 3 months and in only 1.4% of patients at 6 months after the operation. Urethral stricture at 6 months after the surgery was found in 1.4% of patients, whereas bladder neck sclerosis was found in only 0.9% of these cases. No significant difference was observed between these complication frequencies and any preoperative factors or energy source. Conclusions: All EEP types are safe with equal rates of complications intraoperatively, postoperatively, and at 6 months follow-up.

A Novel Technique Using a Thulium Fiber Laser for Simultaneous Percutaneous Nephrolithotomy and Transpelvic Endopyelotomy for High-Insertion Ureteropelvic Junction Obstruction

Background: Endopyelotomy is a minimally invasive option for treatment of ureteropelvic junction (UPJ) obstruction. Although largely supplanted by laparoscopic or robot-assisted laparoscopic pyeloplasty, it retains efficacy and utility in the absence of a crossing vessel in patients not fit for laparoscopy, patients with secondary obstructions or strictures, or those with stones requiring simultaneous treatment. Antegrade endopyelotomy is most commonly performed with scissors, cold knife, or more recently, using a Holmium laser. Herein we present the first reported case of simultaneous antegrade endopyelotomy and percutaneous nephrolithotomy (PCNL) using a thulium fiber laser (TFL). Case Presentation: A 72-year-old male with surgical history of open abdominal aortic aneurysm repair at age 43 years, colon resection, bilateral popliteal artery aneurysms, 5-vessel coronary artery bypass grafting, recent thoracic endovascular aortic repair, and celiac/superior mesenteric artery/bilateral renal stents on Coumadin was referred for gross hematuria and CT urography demonstrating a high-insertion UPJ obstruction without a crossing vessel and 4 caliceal stones, the largest being 2 cm. Given his multiple comorbidities and prior abdominal and retroperitoneal surgeries, he was offered simultaneous PCNL and endopyelotomy to treat both urological conditions with a single procedure. The procedure was accomplished bloodlessly with TFL PCNL and endopyelotomy as an ambulatory procedure with minimal morbidity, immediate resumption of anticoagulation, and rapid convalescence using a special method to convert the high insertion to a dependent insertion. Conclusion: The TFL provides a new effective and efficient tool for the simultaneous endoscopic management of stones and obstructions with minimal bleeding and rapid recovery in select situations.

Dynamic properties of surfactant-enhanced laser-induced vapor bubbles for lithotripsy applications

SIGNIFICANCE

Water is a primary absorber of infrared (IR) laser energy, and urinary stones are immersed in fluid in the urinary tract and irrigated with saline during IR laser lithotripsy. Laser-induced vapor bubbles, formed during lithotripsy, contribute to the stone ablation mechanism and stone retropulsion effects.

AIM

Introduction of a surfactant may enable manipulation of vapor bubble dimensions and duration, potentially for more efficient laser lithotripsy.

APPROACH

A surfactant with concentrations of 0%, 5%, and 10% was tested. A single pulse from a thulium fiber laser with wavelength of 1940 nm was delivered to the surfactant through a 200-μm-core optical fiber, using a wide range of laser parameters, including energies of 0.05 to 0.5 J and pulse durations of 250 to 2500  μs.

RESULTS

Bubble length, width, and duration with surfactant increased on average by 29%, 17%, and 120%, compared with water only.

CONCLUSIONS

Our study demonstrated successful manipulation of laser-induced vapor bubble dimensions and duration using a biocompatible and commercially available surfactant. With further study, use of a surfactant may potentially improve the "popcorn" technique of laser lithotripsy within the confined space of the kidney, enable non-contact laser lithotripsy at longer working distances, and provide more efficient laser lithotripsy.

[Flexible ureteroscopy for lower pole renal stones: novel superpulse thulium (TM) fiber laser lithotripsy]

INTRODUCTION

The SuperPulse Thulium (Tm) fiber laser (wavelength of 1.94 m) has been recently introduced as a directed-energy source for urology. Preclinical studies have shown a significant potential of the SuperPulse Tm fiber laser (SP TFL) for lithotripsy. However, clinical reports of using SP TFL to treat urolithiasis are still few and limited. Of special interest are challenging cases, e.g., lower pole stones, when extreme deflection of the instrument is required.

OBJECTIVE

To evaluate the effectiveness of the SuperPulse Tm fiber laser in the management of lower pole small calyceal stones during flexible ureteroscopy (F-URS).

METHOD

s. The SuperPulse Tm fiber laser device (Urolase 2, IRE Polus, Fryazino, Russia) has been cleared for clinical use by the Ministry of Health of Russian Federation. Study protocol has been approved by the Ethical Review Committee. Between January 2018 and February 2019, 130 patients with kidney stones have undergone Thulium fiber laser lithotripsy during F-URS. We retrospectively analyzed 15 of this patients with a single radiopaque lower pole calculus that were included in the present study. Stone size, stone density, lithotripsy time (from the first to last footswitch press) and "lasering" (laser emission) time were measured. The SP TFL was used for stone disintegration with different settings in dusting and fragmentation modes (0.1 - 4J, 7-300Hz, 6-40W) via a fiber with a 200-m core diameter. Low dose CT scanning was performed on POD 90 to assess SFR.

RESULTS

Stone size ranged from 4 to 17 mm and stone density varied from 350 to 1459 HU. The average lithotripsy time was 12 min (3-30 min). The average "lasering" time was 1.3 min (0.4-2.5 min) and the mean hospital stay was 1.1+/-0.3 days. In all cases we reached the lower pole stone containing calyx with a laser fiber. The complication rates were evaluated by using the Clavien-Dindo grading system and did not exceed GII (6.6%). SFR on POD 90 was achieved in 86.6% of cases.

CONCLUSIONS

F-URS with SuperPulse Tm fiber laser is safe and effective option in the management of lower pole small calyceal stones. The possibility of using small laser fibers gives better instrument deflection which make possible to reach lower pole calyceal stones even with acute lower pole infundibulopelvic angle (IPA).

Endoscopic lithotripsy with a SuperPulsed thulium-fiber laser for ureteral stones: A single-center experience

OBJECTIVES

To estimate the efficacy and safety of SuperPulsed thulium-fiber laser ureteral lithotripsy and to identify optimal laser settings.

METHODS

Patients with solitary stones were prospectively included. Lithotripsy was performed with a SuperPulsed thulium-fiber laser (NTO IRE-Polus, Fryazino, Russia) using a rigid ureteroscope 7.5 Ch (Richard Wolf, Knittlingen, Germany). We analyzed the efficacy of lithotripsy by measuring total energy required for stone disintegration, "laser-on" time, ablation speed, ablation efficacy, and energy consumption. Stone retropulsion and visibility were assessed using a three-point Likert scale. Complications were assessed using the Clavien-Dindo classification system.

RESULTS

A total of 149 patients were included. The mean stone density was 985 ± 360 Hounsfield units, the median (interquartile range) stone volume was 179 (94-357) mm³ . The median (interquartile range) total energy was 1 (0.4-2) kJ, and laser-on time 1.2 (0.5-2.7) min. The median (interquartile range) stone ablation speed was 140 (80-279) mm³ /min, energy for ablation of 1 mm³ was 5.6 (3-9.9) J/mm³ and energy consumption was 0.9 (0.6-1) J/min. A correlation was found between retropulsion and the energy used (r = 0.5, P < 0.001). Multivariable analysis showed energy to be a predictor of increased retropulsion (odds ratio 65.7, 95% confidence interval 1.6-2774.1; P = 0.028). No predictors for worse visibility were identified.

CONCLUSION

The SuperPulsed thulium-fiber laser provides effective and safe lithotripsy during ureteroscopy regardless of stone density. Fiber diameter and laser frequency do not influence visibility or safety. Optimal laser settings are 0.5 J × 30 Hz for fragmentation and 0.15 J × 100 Hz for dusting.

Three-dimensionally printed non-biological simulator for percutaneous nephrolithotomy training

Objective: We sought to improve the educational and pre-operative training on various stages of percutaneous nephrolithotomy (PCNL) under fluoroscopic and ultrasound guidance. We developed a three-dimensional (3D) printed simulator (3D-printed PCNL model) for urological trainees.Methods: 40 s year urology residents were randomly assigned into two groups, completing PCNL surgical steps on a URO Mentor™ surgical simulator (Group A) or on our new 3D-printed PCNL model (Group B). Following the training, both groups completed a standardized questionnaire (Likert scale from 0 to 10) which we used to asses the learning curve associated with PCNL training.Results: The mean score of Group A was 65.2/80 while Group B was 76.1/80. Mann-Whitney U-test showed no significant difference between the groups (U = 16, p < 0.05).Conclusion: The 3D-printed PCNL model developed is a novel and highly effective tool that can facilitate enhanced endourological education and personalized pre-operative planning for urolithiasis cases. According to the criteria tested, residents who used our 3D-printed PCNL models performed better under all metrics.

How Lasers Ablate Stones: In Vitro Study of Laser Lithotripsy (Ho:YAG and Tm-Fiber Lasers) in Different Environments

Introduction: There are two main mechanisms of stone ablation with long-pulsed infrared lasers: photothermal and photomechanical. Which of them is primary in stone destruction is still a matter of discussion. Water holds importance in both mechanisms but plays a major role in the latter. We sought to identify the prevailing mechanism of stone ablation by evaluating the stone mass loss after lithotripsy in different media. Materials and Methods: We tested a holmium:yttrium-aluminum-garnet (Ho:YAG) laser (100 W; Lumenis), a thulium-fiber laser U1 (TFL U1) (120 W; NTO IRE-Polus, Russia), and a SuperPulse thulium-fiber laser U2 (TFL U2) (500 W; NTO IRE-Polus). A single set of laser parameters (15 W = 0.5 J × 30 Hz) was used. Contact lithotripsy was performed in phantoms (BegoStones) in different settings: (a) hydrated phantoms in water, (b) hydrated phantoms in air, (c) dehydrated phantoms in water, and (d) dehydrated phantoms in air. Laser ablation was performed with total energy of 0.3 kJ. Phantom mass loss was defined as the difference between the initial phantom mass and the final phantom mass of the ablated phantoms. Results: All lasers demonstrated effective ablation in hydrated phantoms ablated in water; no visual differences between the lasers were detected. The ablation of dehydrated phantoms in air was also effective with visible vapor during ablation and condensation on the cuvette wall. Dehydrated phantoms in water and in air show minimal to no ablation accompanied with formation of white crust on phantom surface. Among laser types, TFL U2 had the highest phantom mass loss in all groups except for dehydrated phantoms ablated in air. Conclusions: Our results suggest that both photothermal and thermomechanical ablation mechanisms (explosive vaporization) occur in parallel during laser lithotripsy. In Ho:YAG and TFL U2 stone ablation explosive vaporization prevails, whereas in TFL U1 ablation photothermal mechanism appears to predominate.

Safety of a Novel Thulium Fiber Laser for Lithotripsy: An In Vitro Study on the Thermal Effect and Its Impact Factor

Introduction: To investigate the thermal effect on the water by a novel thulium fiber laser (TFL) designed for lithotripsy and evaluate the safety of this laser for clinical use. Materials and Methods: An in vitro experimental setup was constructed. A test tube filled with saline was immersed in an electric water bath, and a TFL fiber and a thermal probe were inserted into it. Saline was irrigated into the tube and pumped out synchronously at the same speed by two pumps, respectively, to maintain convection when needed. Then, continuous TFL firing of different power settings was imposed to saline in the tube for 60 seconds, on the conditions of different irrigation rates. The temperature was recorded every 5 seconds during the whole trial, and each trial was repeated five times. Safety threshold of temperature increase (STTI) was determined comparing with the deemed safe temperature of 43°C in vivo. Results: On condition of 0 mL/min irrigation rate, STTI was 6.5°C, and water temperature increase (WTI) caused by ≥15 W settings surpassed STTI after 20 seconds of laser firing; on condition of 15 mL/min irrigation rate, only WTI caused by the highest 30 W power setting surpassed STTI after 45 seconds of laser firing. When irrigation rate was added up to 25 and 50 mL/min, WTIs caused by all power settings were below STTIs in a 60-second experiment. High frequency and low pulse energy combinations caused a slightly higher WTI compared with low frequency and high pulse energy, given a constant power and irrigation rate. Conclusion: Power setting and irrigation rate collaboratively play a critical role in WTI during TFL lithotripsy, and it is safe to use TFL referring to the thermal effect as long as there is moderate irrigation, while TFL power should be lowered enough when irrigation is ceased.

[Multidisciplinary approach in urology. Laser technologies: faster, simpler, more efficient]

Laser technology has taken a place among the methods of treatment of various urological diseases. The new laser devices are being developed in addition to commonly used. Physicists of the russian NTO "IRE Polus" in collaboration with doctors from Sechenov University have developed a new generation laser device - thulium fiber laser. It has been actively used since 2017 for laser enucleation of prostate. Later the laser was used for treatment of bladder tumor, lithotripsy. The device has already managed to prove its efficacy in in-vitro experiments and clinical practice surpassing foreign analogues.

[Novel approaches for transurethral en-bloc resection of large bladder tumors]

OBJECTIVE

to develop optimal techniques of en-bloc resection of large non-muscle invasive bladder tumors, determine the proper method of specimen extraction and assess the quality of specimens obtained by different techniques.

MATERIALS AND METHODS

A total of 12 patients with primary cT1 bladder cancer underwent transurethral en-bloc resection between January 2018 and March 2019 were enrolled into the study. Tumor size ranged from 3.5 cm to 6.2 cm. For removal and extraction of large bladder tumors using thulium fiber en-bloc laser three different techniques were developed: "swiss cheese technique", "crown and root technique" and "three steps technique" technique". The main pathologic criteria used for assessment of removal technique were tumor grade (G), depth of invasion (T), presence of carcinoma in situ (CIS), variant histology (VH), lymphovascular invasion (LVI), presence of detrusor muscle. Additional criteria were horizontal and vertical resection margin, subclassification of T1-stage and presence of focal necrosis in tumor.

RESULTS

Among the techniques developed and tested, the best quality of specimens for morphological evaluation was obtained using the combined "crown and root technique". First step is electroresection of the exophytic part of the tumor into pieces, and the next step is en-bloc laser resection (using thulium fiber or holmium laser) of the tumor base. Overall, the quality of all specimens obtained using three techniques met the current requirements of pathologic study.

SUMMARY

En-bloc resection techniques of large bladder tumors allow obtaining specimen suitable for proper morphological evaluation and correct tumor staging. Further studies are required to evaluate the impact of these techniques on long-term results of treatment options.

[Micropercutaneous laser nephrolithotripsy]

INTRODUCTION

The least invasive technique of PCNL is micropercutaneous nephrolithotripsy (micro-PCNL). A possibility of kidney puncture under direct endoscopic control with the creation of a working channel sized of 8-4.85 F is a characteristic feature of this system.

AIM

To study the possibilities of micro-PCNL and to determine its role in the treatment of kidney stones.

MATERIALS AND METHODS

A total of 74 patients aged 49.8+/-16.3 years were included in the study. In majority cases an isolated kidney stone was diagnosed (86.4%). The most common stone localization was pelvis (51.5%), followed by lower pole (35.9%). Considering the technical aspects of microPCNL, all patients were divided into 2 groups depending on the stone burden. In 46 patients (62.1%), the stone size was < 1.5 cm, while in 28 patients (37.9%) stones were bigger than 1.5 cm. Prestenting was performed in 54.0% due to renal colic or obstructive pyelonephritis. For the purpose of passive flushing of stone fragments during the lithotripsy, in most patients with a stone size > 1.5 cm, as well as in some prestented patients a ureteral access sheath with a diameter of 10/12 F (56.7%) was placed under x-ray control. In most patients with stones less than 1.5 cm, a 4.85 Ch sheath was utilized. In patients with larger stones, working sheath of 8 Ch was put. For stone disintegration, 50 W and 100 W holmium lasers, as well as the Russian innovative thulium fiber laser were used.

RESULTS

The average duration of surgery from the puncture was 30.6+/-11.6 minutes. The effectiveness was determined by use of a non-contrast computed tomography, performed one month after the surgery. An overall stone-free rate after one-session was 89.1%, and it was 93.4% and 82.4%, respectively, in patients with stones sized less and more than 1.5 cm. In 32.4% cases the stenting was placed due to the large number of small residual fragments and risk of obstruction. In one case, a conversion into a mini-PCNL was done. Two patients (2.7%) required stenting because of renal colic caused by the migration of stone fragments into the ureter. There was no bleeding. In 8.1% of cases, acute pyelonephritis was developed that was treated conservatively. In 9.4% of patients, ESWL was required due to residual stones diagnosed one month after the surgery.

CONCLUSION

Micro-PCNL is highly effective and safe method for treatment of kidney stones. Placing of ureteral access sheath of size 10/12 F contributes to the passive flushing of fragments during lithotripsy, which, together with the use of the 8 F working sheath, makes it possible to effectively perform micro-PCNL in patients with kidney stones larger than 1.5 cm.