Is the holmium:YAG laser the best intracorporeal lithotripter for the ureter? A 3-year retrospective study

[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.

What is the definition of stone dust and how does it compare with clinically insignificant residual fragments? A comprehensive review

PURPOSE

During endoscopic stone surgery, Holmium:YAG (Ho:YAG) and Thulium Fiber Laser (TFL) technologies allow to pulverize urinary stones into fine particles, ie DUST. Yet, currently there is no consensus on the exact definition of DUST. This review aimed to define stone DUST and Clinically Insignificant Residual Fragments (CIRF).

METHODS

Embase, MEDLINE (PubMed) and Cochrane databases were searched for both in vitro and in vivo articles relating to DUST and CIRF definitions, in November 2023, using keyword combinations: "dust", "stones", "urinary calculi", "urolithiasis", "residual fragments", "dusting", "fragments", "lasers" and "clinical insignificant residual fragments".

RESULTS

DUST relates to the fine pulverization of urinary stones, defined in vitro as particles spontaneously floating with a sedimentation duration ≥ 2 sec and suited for aspiration through a 3.6Fr-working channel (WC) of a flexible ureteroscope (FURS). Generally, an upper size limit of 250 µm seems to agree with the definition of DUST. Ho:YAG with and without "Moses Technology", TFL and the recent pulsed-Thulium:YAG (pTm:YAG) can produce DUST, but no perioperative technology can currently measure DUST size. The TFL and pTm:YAG achieve better dusting compared to Ho:YAG. CIRF relates to residual fragments (RF) that are not associated with imminent stone-related events: loin pain, acute renal colic, medical or interventional retreatment. CIRF size definition has decreased from older studies based on Shock Wave Lithotripsy (SWL) (≤ 4 mm) to more recent studies based on FURS (≤ 2 mm) and Percutaneous Nephrolithotomy(PCNL) (≤ 4 mm). RF ≤ 2 mm are associated with lower stone recurrence, regrowth and clinical events rates. While CIRF should be evaluated postoperatively using Non-Contrast Computed Tomography(NCCT), there is no consensus on the best diagnostic modality to assess the presence and quantity of DUST.

CONCLUSION

DUST and CIRF refer to independent entities. DUST is defined in vitro by a stone particle size criteria of 250 µm, translating clinically as particles able to be fully aspirated through a 3.6Fr-WC without blockage. CIRF relates to ≤ 2 RF on postoperative NCCT.

Analysis of lithotripsy efficiency and stone retropulsion displacement according to pulse characteristics of Ho: YAG laser with Moses effect

BACKGROUND AND OBJECTIVES

Compared to the conventional Ho: YAG laser, a Ho: YAG laser device has been reported that has a Moses effect to reduce stone retropulsion and increase lithotripsy efficiency. The principle of this equipment is to convert a single laser pulse into two pulses. Most studies on such lasers are limited to lithotripsy efficiency and the prevention of stone retropulsion; studies according to each pulse condition have not been performed. Therefore, the purpose of this study was to quantify the bubble shape, lithotripsy efficiency, and stone retropulsion displacement in a ureteral phantom according to the modulation of the first pulse characteristics of the Moses effect laser under conditions that maintained the total energy and repetition rate.

MATERIAL AND METHODS

In this study, a Ho: YAG laser system (Holinwon Pro, Wontech Inc., Korea) with an emission wavelength of 2.10 μm and a Moses effect was used. To verify the Moses effect based on the changes in the pulse, a water tank was fabricated, and the ureteral phantom was manufactured in a structure that could be easily installed in the water tank. Additionally, a spherical artificial stone in the ureteral phantom was prepared by mixing calcined gypsum (Cacinated Gypsum) and water at a ratio of 3:1. In the ureteral phantom, a high-speed camera (FASTCAM NOVA S12, Photron Inc.) and visible light were used to record pulse-dependent image analysis of bubbles and stone retropulsion.

RESULT

After mounting the artificial stone in the ureteral phantom, the pulse duration and energy of the first pulse of the Moses effect laser were varied; 30 laser shots for 3 s at a repetition rate of 10 Hz were applied to quantify the lithotripsy efficiency and stone retropulsion displacement, and the experimental values were compared. The fragmentation efficiency was confirmed by measuring the mass before and after the laser pulse application, the original position of the stone retropulsion displacement, and the distance moved. The minimum value of stone retropulsion displacement appeared when the pulse duration of the first pulse was 300 μs, the pulse energy was 100 mJ, and the value was approximately 0.28 mm. The highest fragmentation efficiency was observed under the same conditions, and the mass loss of the artificial stone at that time was approximately 3.7 mg.

CONCLUSION

Quantitative indices, such as lithotripsy efficiency and stone retropulsion displacement, were confirmed using ultrahigh-speed cameras to determine the effect of the first pulse energy and duration of the Ho: YAG laser with the Moses effect on stone removal. It was confirmed that the longer the duration of the primary pulse and the lower the energy, the higher the fragmentation efficiency. In this study, the possibility of manufacturing a laser with an optimal stone-removal effect was confirmed according to the first-pulse condition of the laser with the Moses effect.

How much energy do we need to ablate 1 cubic millimeter of stone during Thulium Fiber Laser lithotripsy? An in vitro study

INTRODUCTION

Both Holmium:yttrium-aluminium-garnet (Ho:YAG) laser and Thulium Fiber Laser (TFL) can effectively treat all urinary stone types. This in vitro study evaluated the ablation volume per pulse (AVP) and required energy needed to ablate 1mm3 (RE, J/mm3) of various stone types at different laser settings with TFL.

METHODS

272-µm core-diameter laser fibers (Boston Scientific©) were connected to a 50 Watts TFL generator (IPG®). An experimental setup immerged human stones of calcium oxalate monohydrate (COM), uric acid (UA), and cystine (CYS) with a single pulse lasing emission (0.5/0.8/1 J), in contact mode. Stones were dried out before three-dimensional scanning to measure AVP and deduce from the pulse energy (PE) and AVP the RE. A direct comparison with known Ho:YAG's AVP and RE was then carried out.

RESULTS

AVP for COM stones was significantly greater than those for CYS stones and similar to UA stones (p = 0.02 and p = 0.06, respectively). If AVP increased with PE against COM and UA stones, AVP decreased against CYS stones. 1 J PE resulted in a threefold lower RE compared with other PE for COM stones. On the contrary, RE for CYS increased with PE, whereas PE did not had influence on RE for UA. TFL was associated with greater AVP for COM, but lower for UA and CYS stones compared to Ho:YAG laser.

CONCLUSION

This in vitro study firstly describes the ablation volume per pulse and required energy to treat a cubic millimeter of three frequent human stone types, and suggest TFL could not be suited for cystine. Therefore, stone composition could be considered when choosing the laser source for lithotripsy.

Initial clinical experience with the pulsed solid-state thulium YAG laser from Dornier during RIRS: first 25 cases

INTRODUCTION

Holmium:yttrium-aluminium-garnet (Ho:YAG) and thulium fiber (TFL) lasers are currently the two laser sources recommended for endocorporeal laser lithotripsy (ELL). Recently, the pulsed-thulium:YAG (Tm:YAG) laser was also proposed for ELL, as an answer to both Ho:YAG and TFL limitations. We aimed to evaluate the efficiency, safety, and laser settings of Tm:YAG laser in ELL during retrograde intrarenal surgery (RIRS).

METHODS

A prospective study of the first 25 patients with ureteral and renal stones who underwent RIRS using the Thulio (pulsed-Tm:YAG, Dornier©, Germany) was performed in a single center. 272 µm laser fibers were used. Stone size, stone density, laser-on time (LOT) and laser settings were recorded. We also assessed the ablation speed (mm3/s), Joules/mm3 and laser power (W) values for each procedure. Postoperative results, such as stone-free rate (SFR) and zero fragments rate (ZFR) were also recorded.

RESULTS

A total of 25 patients were analyzed (Table 1). The median (IQR) age was 55 (44-72) years old. Median (IQR) stone volume was 2849 (916-9153)mm3. Median (IQR) stone density was 1000 (600-1174)HU. Median (IQR) pulse energy, pulse rate and total power were 0.6 (0.6-0,8)J, 15(15-20)Hz and 12(9-16)W, respectively. All procedures used "Captive Fragmenting" pulse modulation (Table 2). The median (IQR) J/mm3 was 14,8 (6-21). The median (IQR) ablation rate was 0,75 (0,46-2)mm3/s. One postoperative complications occurred (streinstrasse). SFR and ZFR were 95% and 55%, respectively.

CONCLUSION

The pulsed-Tm:YAG laser is a safe and effective laser source for lithotripsy during RIRS, using low pulse energy and low pulse frequency.

Thulium fiber laser in endourology: current clinical evidence

PURPOSE OF REVIEW

To review and summarize preclinical and clinical data on thulium fiber laser's (TFL) effectiveness (ablation rate, stone-free rate etc.) and safety in terms of laser injuries and thermal damage. This enables us to assess how the in-vitro evidence translates into the clinical real-life scenario.

RECENT FINDINGS

In this analysis, a total of 21 preclinical trials have been included. Most of the trials use conventional Holmium:YAG laser as a comparator, with only a few assessing lasers with pulse modulation. Most of the trials focus on the superior ablation rate and superior dusting features of TFL, as well as comparison of retropulsion (both in conventional Ho:YAG and in a pulse modulation), with a few studies assessing safety aspects. A total of 13 trials assessed TFL, clinically, in percutaneous nephrolithotomy (PCNL) and retrograde intrarenal surgery (RIRS). The clinical data obtained suggest that lithotripsy by TFL is safe, facilitates effective stone fragmentation, and results in a reduction of retropulsion. Unfortunately, most of the clinical trials lack a direct comparator, and so no clear-cut comparisons are possible.

SUMMARY

During in-vitro studies, TFL demonstrated to be a new energy source with a great potential for improved ablation, lower retropulsion and improved dusting. These claims are supported in contemporary clinical studies, reporting superior ablation and negligible retropulsion in both PCNL and RIRS. However, it should be noted that the data regarding clinical results compared with conventional Ho:YAG is still limited.

Efficacy of various laser devices on lithotripsy in retrograde intrarenal surgery used to treat 1-2 cm kidney stones: A prospective randomized study

AIMS

To compare the efficacy of different laser devices and power ranges on lithotripsy in retrograde intrarenal surgery (RIRS) for 1-2 cm kidney stones.

METHODS

A total of 223 participants undergoing RIRS for 1-2 cm kidney stones at our clinic between January 2015 and January 2017 were recruited for this prospective study (NCT02451319). Two hundred and four participants included in our study were randomly allocated into either ≤20 W with 20 W laser device (group 1) or ≤20 W with 30 W laser device (group 2) or >20 W with 30 W laser device (group 3).

RESULTS

There was no significant difference between the groups in terms of demographic and stone characteristics. Operation and fluoroscopy times were significantly longer (P = .003 and P < .001, respectively) and stone-free rate (SFR) was significantly lower in group 1 (P = .002). Complications were similar in all three groups (P = .512). However, post-operative pain scores were significantly higher in group 1 (P < .001). The multivariate analysis revealed that stone size (95% CI: 0.654-0.878, OR = 0.758, P < .001), ureteral access sheath use (95% CI: 1.003-20.725, OR = 4.560, P = .049), and lithotripsy with 30 W laser device (95% CI: 1.304-11.632, OR = 3.895, P = .015; 95% CI: 1.738-17.281, OR = 5.480, P = .004, groups 2 and 3, respectively) were independent factors predicting SFR for RIRS used in 1-2 cm kidney stones.

CONCLUSION

The 30 W laser device used in RIRS for 1-2 cm kidney stones had shorter operation times, higher SFRs, and lower post-operative pain scores compared with the 20 W device. The 30 W laser device is safe and more efficient in RIRS for treatment of 1-2 cm kidney stones.

How much energy do we need to ablate 1 mm3 of stone during Ho:YAG laser lithotripsy? An in vitro study

INTRODUCTION

Holmium:yttrium-aluminium-garnet (Ho:YAG) is currently the gold standard for lithotripsy for the treatment of all known urinary stone types. Stone composition and volume are major determinants of the lithotripsy. This in vitro study evaluated the required energy to ablate 1 mm³ of various stone types with different laser settings using Ho:YAG.

METHODS

272 µm core-diameter laser fibers (Boston Scientific^©) were connected to a 30 Watt MH1 Ho:YAG generator (Rocamed®). An experimental setup consisting of immerged human stones of calcium oxalate monohydrate (COM), uric acid (UA) or cystine (Cys) was used with a single pulse lasing emission (0.6/0.8/1 J), in contact mode. Stones were dried out before three-dimensional scanning to measure ablation volume per pulse (AVP) and required energy to treat 1 mm³ (RE).

RESULTS

All settings considered, ablation volumes per pulse (AVP) for COM were significantly lower than those for UA and Cys (p = 0.002 and p = 0.03, respectively), whereas AVP for Cys was significantly lower than those for UA (p = 0.03). The mean REs at 0.6 J pulse energy (PE) for COM, Cys and UA were 34, 8.5 and 3.2 J, respectively The mean REs at 1 J PE for COM, Cys and UA were 14.7, 6.4 and 2 J, respectively. At 0.6 J PE, RE for COM was more than tenfold and fivefold higher than those for UA and Cys, respectively.

CONCLUSION

This in vitro study shows for the first time a volumetric evaluation of Ho:YAG efficiency by the ablation volume per pulse on human stone samples, according to various pulse energies. The REs for COM, UA and Cys should be considered in clinical practice.

Comparison of Stone Retrieval Basket, Stone Cone and Holmium Laser: Which One Is Better in Retropulsion and Stone-Free Status for Patients with Upper Ureteral Calculi?

Introduction: Transurethral lithotripsy (TUL) is an appropriate treatment for ureteral stones and is usually used for stones in the middle and lower part of the ureter. Different devices such as the Holmium laser, the stone basket, and the stone cone exist to prevent any fragments from retropulsion during TUL. The present study aims to compare the advantages and disadvantages of the Holmium laser, the stone basket, and the stone cone. Methods: A retrospective study was conducted from September 2016 to January 2018 comparing various TUL methods in 88 subjects with proximal ureteral calculi. The study participants were divided into 4 matched groups. The first one included 20 patients undergoing TUL with no device (group 1), the second group included 22 patients undergoing TUL while using the stone retrieval basket, the third group included 18 patients undergoing TUL while utilizing the stone cone and the fourth group included 28 patients undergoing TUL while using the Hol-YAG laser. Results: A residual stone ≥3 mm was recorded in 15.9% of the patients. The stone free rate was seen in 100%, 90.9, 83.3%, and 55% of the Holmium laser group, the retrieval basket group, the stone cone group and the no device group respectively (P=0.001). The lowest rate of surgery complications including ureteral perforation, post-operative fever, and mucosal damage between the 4 groups (P=0.003) and the highest time of surgery (P=0.001) belonged to the laser group. If we want to ignore the laser group, the success rate for lithotripsy was better in both groups with a stone retrieval device compared to the no device group, but no advantage existed between the stone basket and the stone cone. Conclusion: We can safely conclude that lasers significantly help to prevent stone migration during TUL. If we want to ignore the laser group, the success rate for lithotripsy was significantly better in both groups with a stone retrieval device compared to the no device group, but no advantage existed between the stone basket and the stone cone.

Role of lasers in urology

Laser technology has long been a standard treatment for many diseases. In particular, laser treatment is considered the standard of care in various urological diseases. While originally primarily restricted to stone treatment, lasers have since evolved to play an important role even in the treatment of malignant diseases. In this review, we take a closer look at the history of lasers in urology and some implications for treatments today.

Retrograde intrarenal surgery: An expanding role in treatment of urolithiasis

During the past 3 decades, the surgical management of kidney stones has undergone many technological advances and one is the development of the flexible ureteroscopy. The development of this instrument as well as ancillary equipment such as baskets, graspers, and others, and improvements in lithotripsy with Holmium: YAG laser have led to expand its indications with diagnostic and therapeutic management of medical issues of the upper urinary tract such as urolithiasis and urothelial tumors. The objective of this review is to describe its indications and results in the different scenarios for the treatment of urinary stones.

Moses technology in a stone simulator

INTRODUCTION

The objective of this study was to compare fragmentation efficiency of the conventional regular mode of holmium laser to the Moses contact mode on a stone simulator.

METHODS

The Lumenis^® Pulse^TM P120 H holmium laser system, together with Moses D/F/L fibers were used to compare regular mode with Moses contact mode in a stone simulator model using flexible ureteroscopy with artificial stones. Efficiency of laser lithotripsy was measured by procedural time. Degree of stone retropulsion was also compared between regular and Moses modes using a Likert scale from 0 (no retropulsion) to 3 (maximum retropulsion).

RESULTS

Using the stone simulator model, a significant reduction in stone retropulsion was noticed when comparing regular mode to the Moses contact mode (mean Grade 2.5 vs. Grade 1; p<0.01). When compared with the regular mode, the Moses contact mode was associated with significantly shorter procedural time during fragmentation (13.9 vs. 9.1 minutes; p≤0.01) and dusting (9.3 vs. 7.1 minutes; p≤0.01). In addition, when compared with the regular mode, the laser pedal was pressed significantly less often with the Moses mode during fragmentation (86 vs. 43 times; p<0.01) and dusting (50 vs. 26 times; p<0.01). Moses contact mode was associated with significantly higher percentage of lasing vs. pausing when compared with the regular mode for both fragmentation (0.8 J/10 Hz) and pulverization (0.4 J/50 Hz) settings (both p<0.05).

CONCLUSIONS

Using the stone simulator setup, Moses technology was associated with more efficient laser lithotripsy (shorter operative time) due to significantly reduced stone retropulsion.

In vitro investigations of propulsion during laser lithotripsy using video tracking

OBJECTIVES

Ureteroscopic laser lithotripsy is an important and widely used method for destroying ureter stones. It represents an alternative to ultrasonic and pneumatic lithotripsy techniques. Although these techniques have been thoroughly investigated, the influence of some physical parameters that may be relevant to further improve the treatment results is not fully understood. One crucial topic is the propulsive stone movement induced by the applied laser pulses. To simplify and speed up the optimization of laser parameters in this regard, a video tracking method was developed in connection with a vertical column setup that allows recording and subsequently analyzing the propulsive stone movement in dependence of different laser parameters in a particularly convenient and fast manner.

MATERIALS AND METHODS

Pulsed laser light was applied from below to a cubic BegoStone phantom loosely guided within a vertical column setup. The video tracking method uses an algorithm to determine the vertical stone position in each frame of the recorded scene. The time-dependence of the vertical stone position is characterized by an irregular series of peaks. By analyzing the slopes of the peaks in this signal it was possible to determine the mean upward stone velocity for a whole pulse train and to compare it for different laser settings. For a proof of principle of the video tracking method, a specific pulse energy setting (1 J/pulse) was used in combination with three different pulse durations: short pulse (0.3 ms), medium pulse (0.6 ms), and long pulse (1.0 ms). The three pulse durations were compared in terms of their influence on the propulsive stone movement in terms of upward velocity. Furthermore, the propulsions induced by two different pulse energy settings (0.8 J/pulse and 1.2 J/pulse) for a fixed pulse duration (0.3 ms) were compared. A pulse repetition rate of 10 Hz was chosen for all experiments, and for each laser setting, the experiment was repeated on 15 different freshly prepared stones. The latter set of experiments was compared with the results of previous propulsion measurements performed with a pendulum setup.

RESULTS

For a fixed pulse energy (1 J/pulse), the mean upward propulsion velocity increased (from 120.0 to 154.9 mm · s^-1 ) with decreasing pulse duration. For fixed pulse duration (0.3 ms), the mean upward propulsion velocity increased (from 91.9 to 123.3 mm · s^-1 ) with increasing pulse energy (0.8 J/pulse and 1.2 J/pulse). The latter result corresponds roughly to the one obtained with the pendulum setup (increase from 61 to 105 mm · s^-1 ). While the mean propulsion velocities for the two different pulse energies were found to differ significantly (P < 0.001) for the two experimental and analysis methods, the standard deviations of the measured mean propulsion velocities were considerably smaller in case of the vertical column method with video tracking (12% and 15% for n = 15 freshly prepared stones) than in case of the pendulum method (26% and 41% for n = 50 freshly prepared stones), in spite of the considerably smaller number of experiment repetitions ("sample size") in the first case.

CONCLUSION

The proposed vertical column method with video tracking appears advantageous compared to the pendulum method in terms of the statistical significance of the obtained results. This may partly be understood by the fact that the entire motion of the stones contributes to the data analysis, rather than just their maximum distance from the initial position. The key difference is, however, that the pendulum method involves only one single laser pulse in each experiment run, which renders this method rather tedious to perform. Furthermore, the video tracking method appears much better suited to model a clinical lithotripsy intervention that utilizes longer series of laser pulses at higher repetition rates. The proposed video tracking method can conveniently and quickly deliver results for a large number of laser pulses that can easily be averaged. An optimization of laser settings to achieve minimal propulsive stone movement should thus be more easily feasible with the video tracking method in connection with the vertical column setup. Lasers Surg. Med. 50:333-339, 2018. © 2017 Wiley Periodicals, Inc.

Flexible ureteroscopy: technique, tips and tricks

During the last decades, the surgical management of kidney stones benefited of many technological advances and one of them is the development of flexible ureteroscopy (fURS). This tool, ancillary equipment such as graspers and baskets, and lithotripsy technique with Holmium:YAG laser underwent many improvements leading to a widening of its indications with diagnostic and therapeutic management of upper urinary tract pathologies such as urolithiasis and urothelial tumors. The objective of this review is to describe the surgical technique for fURS as well as tips and tricks for the treatment of renal stones.

Initial Clinical Experience with a Modulated Holmium Laser Pulse-Moses Technology: Does It Enhance Laser Lithotripsy Efficacy?

OBJECTIVE

The Lumenis^® High-power Holmium Laser (120H) has a unique modulated pulse mode, Moses™ technology. Moses technology modulates the laser pulse to separate the water (vapor bubble), then deliver the remaining energy through the bubble. Proprietary laser fibers were designed for the Moses technology. Our aim was to compare stone lithotripsy with and without the Moses technology.

METHODS

We designed a questionnaire for the urologist to fill immediately after each ureteroscopy in which the Lumenis 120H was used. We compared procedures with (n=23) and without (n=11) the use of Moses technology. Surgeons ranked the Moses technology in 23 procedures, in comparison to regular lithotripsy (worse, equivalent, better, much better). Laser working time and energy use were collected from the Lumenis 120H log.

RESULTS

During 4 months, five urologists used the Lumenis 120H in 34 ureteroscopy procedures (19 kidney stones, 15 ureteral stones; 22 procedures with a flexible ureteroscope, and 12 with a semi-rigid ureteroscope). Three urologists ranked Moses technology as much better or better in 17 procedures. In 2 cases, it was ranked equivalent, and in 4 cases ranking was not done. Overall, laser lithotripsy with Moses technology utilized laser energy in less time to achieve a satisfying stone fragmentation rate of 95.8 mm³/min versus 58.1 mm³/min, P=0.19. However, this did not reach statistical significance.

CONCLUSION

The new Moses laser technology demonstrated good stone fragmentation capabilities when used in everyday clinical practice.

In vitro investigation on Ho:YAG laser-assisted bone ablation underwater

Liquid-assisted hard tissue ablation by infrared lasers has extensive clinical application. However, detailed studies are still needed to explore the underlying mechanism. In the present study, the dynamic process of bubble evolution induced by Ho:YAG laser under water without and with bone tissue at different thickness layer were studied, as well as its effects on hard tissue ablation. The results showed that the Ho:YAG laser was capable of ablating hard bone tissue effectively in underwater conditions. The penetration of Ho:YAG laser can be significantly increased up to about 4 mm with the assistance of bubble. The hydrokinetic forces associated with the bubble not only contributed to reducing the thermal injury to peripheral tissue, but also enhanced the ablation efficiency and improve the ablation crater morphology. The data also presented some clues to optimal selection of irradiation parameters and provided additional knowledge of the bubble-assisted hard tissue ablation mechanism.

Tissue damage by laser radiation: an in vitro comparison between Tm:YAG and Ho:YAG laser on a porcine kidney model

The understanding of tissue damage by laser radiation is very important for the safety in the application of surgical lasers. The objective of this study is to evaluate cutting, vaporization and coagulation properties of the 2 µm Tm:YAG laser (LISA Laser Products OHG, GER) in comparison to the 2.1 µm Ho:YAG laser (Coherent Medical Group, USA) at different laser power settings in an in vitro model of freshly harvested porcine kidneys. Laser radiation of both laser generators was delivered by using a laser fiber with an optical core diameter of 550 µm (RigiFib, LISA Laser GER). Freshly harvested porcine kidneys were used as tissue model. Experiments were either performed in ambient air or in aqueous saline. The Tm:YAG laser was adjusted to 5 W for low and 120 W for the high power setting. The Ho:YAG laser was adjusted to 0.5 J and 10 Hz (5 W average power) for low power setting and to 2.0 J and 40 Hz (80 W average power) for high power setting, accordingly. The specimens of the cutting experiments were fixed in 4 % formalin, embedded in paraffin and stained with Toluidin blue. The laser damage zone was measured under microscope as the main evaluation criteria. Laser damage zone consists of an outer coagulation zone plus a further necrotic zone. In the ambient air experiments the laser damage zone for the low power setting was 745 ± 119 µm for the Tm:YAG and 614 ± 187 µm for the Ho:YAG laser. On the high power setting, the damage zone was 760 ± 167 µm for Tm:YAG and 715 ± 142 µm for Ho:YAG. The incision depth in ambient air on the low power setting was 346 ± 199 µm for Tm:YAG, 118 ± 119 µm for Ho:YAG. On the high power setting incision depth was 5083 ± 144 µm (Tm:YAG) and 1126 ± 383 µm (Ho:YAG) respectively. In the saline solution experiments, the laser damage zone was 550 ± 137 µm (Tm:YAG) versus 447 ± 65 µm (Ho:YAG), on the low power setting and 653 ± 137 µm (Tm:YAG) versus 677 ± 134 µm (Ho:YAG) on the high power setting. Incision depth was 1214 ± 888 µm for Ho:YAG whereas Tm:YAG did not cut tissue at 5 W in saline solution. On the high power setting, the incision depth was 4050 ± 1058 µm for Tm:YAG and 4083 ± 520 µm for Ho:YAG. Both lasers create similar laser damage zones of <1 mm in ambient air and in saline solution. These in vitro experiments correspond well with in vivo experiments. Thereby, Tm:YAG offers a cutting performance, coagulation and safety profile similar to the standard Ho:YAG lasers in urological surgery.

Is semirigid ureteroscopy sufficient in the treatment of proximal ureteral stones? When is combined therapy with flexible ureteroscopy needed?

The goals of this study were to examine cases of proximal ureteral stones in which semirigid or flexible ureteroscopes alone were insufficient for endoscopic treatment, requiring the combination of both. A total of 137 patients were retrospectively evaluated. Holmium laser was used as the energy source for stone fragmentation. Each operation was begun with a 6/7.5 Fr semirigid ureteroscope (URS), and continued with a 7.5 Fr flexible URS in those procedures that failed to reach the stone or push-up. Double J stents were inserted into those patients in whom the flexible URS failed. Shock wave lithotripsy (SWL) or a repeat ureteroscopy (after 2-4 weeks) was planned in those patients who were considered to be treated unsuccessfully. The demographic features of the patients, stone sizes, treatment outcomes, need for additional treatment, complications, and the results of the postoperative 1-month early follow-up were evaluated. The mean age of the patients (77 males and 60 females) was 38 ± 6.7 years old, the mean stone size was 12.3 ± 3.7 mm, and the number of patients with persistent hydronephrosis was 86 (62.8 %). A stone-free diagnosis was achieved in a total of 124 patients (90.5 %), using a semirigid URS in 80 patients and a flexible URS in 44 patients. Treatment using a flexible URS was administered in 38 patients (27.7 %) due to push-up, and in 6 patients (4.3 %) because of the failure to advance the semirigid URS into the ureter. The treatment failed in 13 patients (9.4 %) despite the use of both methods. Treatment using low-caliber semirigid ureteroscopy and a holmium laser is possible, regardless of the stone size, in female patients without hydronephrosis. However, the need for combined treatment with flexible ureteroscopy is increased in male patients with hydronephrosis.

Safety and efficacy of using the stone cone and an entrapment and extraction device in ureteroscopic lithotripsy for ureteric stones

Objective

To assess the safety and efficacy of using a stone cone and an entrapment and extraction device (N-Trap®, Cook Urological, Bloomington, IN, USA) to avoid stone retropulsion during ureteroscopic lithotripsy for ureteric stones.

Patients and methods

This retrospective comparative study included 436 patients treated with ureteroscopic lithotripsy for a single ureteric stone from February 2011 to January 2014. The diagnosis of a stone was confirmed by plain spiral computed tomography in all cases. Patients were divided according to the ureteric occlusion device applied to avoid stone retropulsion during pneumatic lithotripsy into three groups; group 1 (156) had no instruments used, group 2 (140) in whom the stone cone was applied, and group 3 (140) in whom the N-Trap was used. Patient demographics, stone criteria, operative duration and complications, and success rates (complete stone disintegration with no upward migration) were reported and analysed statistically.

Results

The stone was in the lower ureter in >55% of patients in all groups. The mean (SD) of maximum stone length was 9.8 (2.5), 10.4 (2.8) and 9.7 (2.9) in groups 1–3, respectively. The use of the stone cone or N-Trap did not significantly increase the operative duration (P = 0.13) or complication rates (P = 0.67). There was a statistically significant difference (P < 0.001) favouring groups 2 and 3 for retropulsion and success rates, being 83.3% in group 1, 97.1% in group 2 and 95.7% in group 3.

Conclusion

The stone cone and N-Trap gave high success rates in preventing stone retropulsion during ureteric pneumatic lithotripsy. Both devices caused no increase in operative duration or complications when used cautiously.

Predictive factors for flexible ureterorenoscopy requirement after rigid ureterorenoscopy in cases with renal pelvic stones sized 1 to 2 cm

Purpose

To evaluate the outcomes of rigid ureterorenoscopy (URS) for renal pelvic stones (RPS) sized 1 to 2 cm and to determine the predictive factors for the requirement for flexible URS (F-URS) when rigid URS fails.

Materials and Methods

A total of 88 patients were included into the study. In 48 patients, the RPS were totally fragmented with rigid URS and F-URS was not required (group 1). In 40 patients, rigid URS was not able to access the renal pelvis or fragmentation of the stones was not completed owing to stone position or displacement and F-URS was utilized for retrograde intrarenal surgery (RIRS) (group 2). The predictive factors for F-URS requirement during RIRS for RPS were evaluated. Both groups were compared regarding age, height, sex, body mass index, stone size, stone opacity, hydronephrosis, and previous treatments.

Results

The mean patient age was 48.6±16.5 years and the mean follow-period was 39±11.5 weeks. The overall stone-free rate in the study population was 85% (75 patients). In groups 1 and 2, the overall stone-free rates were 83% (40 patients) and 87% (35 patients), respectively (p>0.05). The independent predictors of requirement for F-URS during RIRS were male gender, patient height, and higher degree of hydronephrosis.

Conclusions

Rigid URS can be utilized in selected patients for the fragmentation of RPS sized 1 to 2 cm with outcomes similar to that of F-URS. In case of failure of rigid URS, F-URS can be performed successfully in this group of patients.

Systematic evaluation of a holmium:yttrium-aluminum-garnet laser lithotripsy device with variable pulse peak power and pulse duration

OBJECTIVE

The Holmium:yttrium-aluminum-garnet (Ho:YAG) laser is the standard lithotrite for ureteroscopy. This paper is to evaluate a Ho:YAG laser with a novel effect function in vitro, which allows a real-time variation of pulse duration and pulse peak power.

METHODS

Two types of phantom calculi with four degrees of hardness were made for fragmentation and retropulsion experiments. Fragmentation was analysed at 5 (0.5 J/10 Hz), 10 (1 J/10 Hz), and 20 (2 J/10 Hz) W in non-floating phantom calculi, retropulsion in an ureteral model at 10 (1 J/10 Hz) and 20 (2 J/10 Hz) W using floating phantom calculi. The effect function was set to 25%, 50%, 75%, and 100% of the maximum possible effect function at each power setting. Primary outcomes: fragmentation (mm3), the distance of retropulsion (cm); ≥5 measurements for each trial.

RESULTS

An increase of the effect feature (25% vs. 100%), i.e., an increase of pulse peak power and decrease of pulse duration, improved Ho:YAG laser fragmentation. This effect was remarkable in soft stone composition, while there was a trend for improved fragmentation with an increase of the effect feature in hard stone composition. Retropulsion increased with increasing effect function, independently of stone composition. The major limitations of the study are the use of artificial stones and the in vitro setup.

CONCLUSION

Changes in pulse duration and pulse peak power may lead to improved stone fragmentation, most prominently in soft stones, but also lead to increased retropulsion. This new effect function may enhance Ho:YAG laser fragmentation when maximum power output is limited or retropulsion is excluded.

Efficacy and safety of Ho:YAG laser lithotripsy for ureteroscopic removal of proximal and distal ureteral calculi

Background

Laser lithotripsy is an established endourological modality. Ho:YAG laser have broadened the indications for ureteroscopic stone managements to include larger stone sizes throughout the whole upper urinary tract. Aim of current work is to assess efficacy and safety of Ho:YAG laser lithotripsy during retrograde ureteroscopic management of ureteral calculi in different locations.

Methods

88 patients were treated with ureteroscopic Ho:YAG laser lithotripsy in our institute. Study endpoint was the number of treatments until the patient was stone-free. Patients were classified according to the location of their stones as Group I (distal ureteric stones, 51 patients) and group II (proximal ureteral stones, 37). Group I patients have larger stones as Group II (10.70 mm vs. 8.24 mm, respectively, P = 0.020).

Results

Overall stone free rate for both groups was 95.8%. The mean number of procedures for proximal calculi was 1.1 ± 0.1 (1–3) and for distal calculi was 1.0 ± 0.0. The initial treatment was more successful in patients with distal ureteral calculi (100% vs. 82.40%, respectively, P = 0.008). No significant difference in the stone free rate was noticed after the second laser procedure for stones smaller versus larger than 10 mm (100% versus 94.1%, P = 0.13). Overall complication rate was 7.9% (Clavien II und IIIb). Overall and grade-adjusted complication rates were not dependant on the stone location. No laser induced complications were noticed.

Conclusions

The use of the Ho:YAG laser appears to be an adequate tool to disintegrate ureteral calculi independent of primary location. Combination of the semirigid and flexible ureteroscopes as well as the appropriate endourologic tools could likely improve the stone clearance rates for proximal calculi regardless of stone-size.

Effectiveness of Flexible Ureterorenoscopy and Laser Lithotripsy for Multiple Unilateral Intrarenal Stones Smaller Than 2 cm

Purpose. To evaluate the safety and efficacy of RIRS for the treatment of multiple unilateral intrarenal stones smaller than 20 mm. Methods. Between March 2007 and April 2013, patients with multiple intrarenal stones smaller than 20 mm were treated with RIRS and evaluated retrospectively. Each patient was evaluated for stone number, stone burden (cumulative stone length), operative time, SFRs, and complications. Results. 173 intrarenal stones in 48 patients were included. Mean age, mean number of stones per patient, mean stone burden, and mean operative time were 40.2 ± 10.9 years (23–63), 3.6 ± 3.0 (2–18), 22.2 ± 8.4 mm (12–45), and 60.3 ± 22.0 minutes (30–130), respectively. The overall SFR was 91.7%. SFRs for patients with a stone burden less and greater than 20 mm were 100% (23/23) and 84% (21/25), respectively (χ² = 26.022, P < 0.001). Complications occurred in six (12.5%–6/48) patients, including urinary tract infection or high-grade fever >38.5°C in three cases, prolonged hematuria in two cases, and ureteral perforation in one case, all of whom were treated conservatively. No major complications occurred. Conclusions. RIRS is an effective treatment option in patients with multiple unilateral intrarenal stones especially when the total stone burden is less than 20 mm.

[Ureteroscopy: is it the best?]

Over the last 40 years the treatment of urolithiasis passed from open surgical therapies to minimally invasive approaches. From the introduction of the first ureteroscopes in '80s many technological improvements allowed to reduce endourological instruments' size, ensuring in the meanwhile an increasingly high success rate in the resolution of the urolithiasis. The purpose of the study is to review the current role of the ureteroscopy(URS) in the treatment of urinary stones. A non-systematic review was performed considering the most recent Guidelines and results from Literature. The results confirm that, considering ureteral calculi, the stone-free rate (SFR) for URS is significantly higher than for ESWL in the treatment of distal ureteral stones <10 mm and >10 mm. Endoscopy has a first-line role also in the treatment of proximal ureteral stones >10 mm, together with ESWL. Retreatment rate and ancillary procedures are also lower in patients treated with URS, despite it is more invasive if compared with ESWL. Recent data are available in Literature about the treatment of nephrolithiasis with Retrograde Intra-Renal Surgery (RIRS). RIRS is the first-line treatment, together with ESWL, for stones <20 mm, and second choice for stones >20 mm. However, for large renal stones the role of RIRS is still being discussed. In conclusion, the majority of urinary stones can be treated by rigid or flexible URS. Further studies are required to clarify the role of endoscopy in the treatment of large stones, especially if compared to percutaneous approaches.

Holmium:YAG laser ureteroscopic lithotripsy for ureteric calculi in children: predictive factors for complications and success

OBJECTIVES

To evaluate the impact of age, stone size, location, radiolucency, extraction of stone fragments, size of ureteroscope and presence and degree of hydronephrosis on the efficacy and safety of holmium:YAG (Ho:YAG) laser lithotripsy in the ureteroscopic treatment of ureteral stones in children.

METHODS

Between October 2011 and May 2013, a total of 104 patients were managed using semirigid Ho:YAG ureterolithotripsy. Patient age, stone size and site, radiolucency, use of extraction devices, degree of hydronephrosis and size of ureteroscope were compared for operative time, success and complications.

RESULTS

In all, 128 URS were done with a mean age of 4.7 years. The mean stones size was 11 mm. Success rate was 81.25 %. Causes of failure were 12.5 % access failure, 1.5 % extravasation and 4.7 % stone migration. Overall complications were 23.4 %. Failure of dilatation and extravasation were detected only in children <2 years old. Extravasation was significantly higher in smaller ureters and cases with stone size >15 mm. Stone migration was significantly higher in upper ureteric stones.

CONCLUSIONS

Failure and complications rates in Ho:YAG ureterolithotripsy were significantly affected by younger age (<2 years), upper ureteric stones and smaller ureters but were not related to stone radiolucency or degree of hydronephrosis. Larger stones (>15 mm) were associated with increased complications. After multivariate analysis, the age of the patients remained significant predictor for failure of dilatation and stone migration, while size of the ureter was the only significant predicting factor for failure.

Comparative study of outcome in treating upper ureteral impacted stones using minimally invasive percutaneous nephrolithotomy with aid of patented system or transurethral ureteroscopy

OBJECTIVE

To determine an efficient method for treating upper ureteral impacted stones, we compared the outcome of minimally invasive percutaneous nephrolithotomy with the aid of our patented system and transurethral ureteroscopy.

MATERIALS AND METHODS

A total of 182 patients with complicated impacted upper ureteral stones above the level of L4 were randomly divided into 2 groups. Group 1 included 91 patients who were treated with minimally invasive percutaneous nephrolithotomy with the aid of a patented system. Group 2 included 91 patients who were treated with ureteroscopy. The patients underwent postoperative shock wave lithotripsy, when necessary. The operative time, stone clearance rate, operative complication markers (amount of intraoperative bleeding and postoperative fever rate), and cost of treatment were compared.

RESULTS

A significantly shorter operative time, greater rate of stone clearance, lower need for postoperative shock wave lithotripsy, and lower rate of postoperative fever was found in group 1 than in group 2 (P <.05). However, the cost of treatment and amount of intraoperative bleeding were significantly greater.

CONCLUSION

We believe minimally invasive percutaneous nephrolithotomy with the aid of the patented system could be the first choice in treating complicated impacted upper ureteral stones above the level of L4.

Simultaneous saline irrigation during retrograde rigid ureteroscopic lasertripsy for the prevention of proximal calculus migration

OBJECTIVE

In this paper, we analyze the clinical efficacy of a simultaneous saline irrigation method in treating upper-mid ureteral stone migration and evaluate its effectiveness during ureteroscopic lasertripsy.

METHODS

We prospectively evaluated 78 patients with a total of 95 upper-mid ureteral stones, which were treated with holmium:YAG lasertripsy. These patients were randomized into 2 groups. In Group 1 (39 cases with 44 ureteral stones), conventional ureteroscopic lasertripsy was performed. In Group 2, (39 cases with 51 ureteral stones), the simultaneous saline irrigation method was used during lasertripsy. There was no significant difference between the groups with regards to stone site, size or state of the upper urinary tract by spiral computed tomography or excretory urography. Data were analyzed regarding stone migration, lengths of time, and ureteral clearing for various stages of each procedure.

RESULTS

One patient in Group 2 (2%) experienced upward stone migration, while this occurred in 8 patients in Group 1 (20%). The operative time in Group 1 ranged from 35 to 55 minutes (mean: 44.8 ± 5.3), while in Group 2 it ranged from 40 to 69 minutes (mean: 50.4±3). There was no significant different in the operative times between the two groups (p < 0.05). Ureteral perforation, urinoma and urosepsis were not seen in both groups.

CONCLUSION

The simultaneous saline irrigation method demonstrated a statistically significant advantage over conventional methods. The operation can be performed persistently under clear vision, and since the stones cannot move upward, fragmented portions are easily flushed out. Our data suggest that this method is simple, safe and effective in preventing proximal stone migration during ureteroscopic lasertripsy.

Intracorporeal laser lithotripsy

Objectives

To review the current literature on intracorporeal laser lithotripsy.

Methods

We searched PubMed for relevant reports up to January 2012, using the keywords ‘laser’, ‘lithotripsy’ and ‘intracorporeal’.

Results

We studied 125 relevant reports of studies with various levels of evidence. Efficient lithotripsy depends on the laser variables (wavelength, pulse duration and pulse energy) and the physical properties of the stones (optical, mechanical and chemical). The most efficient laser for stones in all locations and of all mineral compositions is the holmium yttrium–aluminium–garnet laser (Ho:YAG). The frequency-doubled double-pulse Nd:YAG laser functions through the generation of a plasma bubble. New laser systems, such as the erbium:YAG and the thulium laser, are under evaluation. Laser protection systems have also been developed for the novel digital flexible ureteroscopes. Although complications are rare, a high relevant clinical suspicion is necessary.

Conclusions

Laser lithotripsy technology is continuously developing, while the Ho:YAG laser remains the reference standard for intracorporeal lithotripsy.

Endoscopic holmium laser treatment for ureterolithiasis

INTRODUCTION

The rapid development and invention of ever more technologically advanced ureterorenoscopes as well as other instruments used in fragmenting ureteral stones have made the traditional surgical treatment of ureterolithiasis very rare.

MATERIAL AND METHODS

We investigated 727 patients treated for ureterolithiasis. 769 ureteroscopic lithotripsies (URSL) with the holmium laser were performed. We evaluated the relation of the stone size, the section of the ureter involved, length of time of the stone within the ureter and the condition of the urinary tract to the results of the ureterolithiasis treatment.

RESULTS

A good result of breaking up the stone and passing its fragments out of the ureter within 3 months following the first URSL was observed in 642 (90.9%) out of 706 patients. The remaining 64 (9.1%) patients required additional procedures: ESWL was performed on 44 patients; URSL was repeated for 20 patients. The most serious early post-URSL complications involved: urinary tract infection with symptoms of urosepsis in 10 patients, leading to death in 1 case, ureteral perforation in 3 patients, including 1 case presenting a periureteral leak that necessitated a surgical intervention.

CONCLUSIONS

URSL with the holmium laser is an effective and safe method for treating ureterolithiasis.

Effectiveness of single flexible ureteroscopy for multiple renal calculi

PURPOSE

To assess effectiveness of flexible ureteroscopy (fURS) in patients not with simple but with multiple unilateral renal stones.

PATIENTS AND METHODS

A database analysis was performed to identify patients with multiple unilateral intrarenal stones. Patients were treated using an 8.8F flexible ureteroscope. Patients were considered stone free if no residual stones were seen endoscopically and radiographically after the procedure. The efficiency and the safety of the procedures were analyzed.

RESULTS

Between 2006 and 2008, 1054 ureteroscopic procedures were performed in our department; 125 patients met the inclusion criteria. Holmium:yttrium-aluminum-garnet laser lithotripsy was necessary in 41 (32.8%) patients. The mean stone size was 11.93 ± 8.2 mm, with a mean stone burden of 83.7 ± 67.66 mm(2). The mean number of stones was 3.59 ± 3.57. Twenty-six (20.8%) patients had a stone burden ≥ 100 mm(2), and 99 (79.2%) a stone burden <100 mm(2). The overall stone-free rate after a single procedure of fURS was 74.4%. In the remaining 32 patients with residual stones, the mean stone burden dropped from 123.24 ± 84.36 mm(2) to 56.28 ± 52.53 mm(2). The stone-free rate in patients with a stone burden ≥ 100 mm(2) was 65.4% and 79.5% in patients with a stone burden < 100 mm(2), respectively. Complications have been recorded in seven (5.6%) patients, including urinary tract infection in four, ureteral perforation in one, and hematuria in two patients. No major complications occurred. All patients were treated conservatively.

CONCLUSIONS

fURS is an effective treatment option in patients with multiple unilateral renal stones. Single procedure stone-free rates are high with a low rate of only minor complications.

Stentless pediatric ureteroscopic holmium: YAG laser stone disintegration: is gravels retrieval an issue?

PURPOSE

To evaluate the safety and efficacy of stentless pediatric ureteroscopic holmium laser stone disintegration without gravels retrieval.

PATIENTS AND METHODS

From Feb 2007 to Feb 2010, 21 children (12 boys and 9 girls) with unilateral single stone ureter, with an average age of 8.5 years (range 4-12 years), were treated with 6.9 Fr semirigid ureteroscope for a stone size ranged from 5 to 10 mm (mean 6.5 mm). All the stones were radioopaque, located in the upper ureter in 2 cases (9.5%), in the middle ureter in 5 cases (24%), and in the lower ureter in 14 cases (66.5%). Complete holmium laser stone disintegration was applied in all cases without gravels removal. No postoperative ureteral stent was inserted in any case.

RESULTS

The stones were successfully approached and completely disintegrated in a single session in 20 cases (95.2%). All the procedures were done without ureteral orifice dilatation apart from 3 cases where another working guide wire was applied. No intraoperative complications were recorded in the form of mucosal injury, ureteral perforation, or urinary extravasation. There is no early postoperative complication in the form of urinary tract infection or colic apart from single case of hematuria which was successfully treated conservatively. Two weeks postoperatively, KUB (kidney, ureter, and bladder) films were completely free from any significant gravel (>3 mm) and US showed no hydronephrosis.

CONCLUSION

Stentless ureteroscopic holmium laser disintegration without gravels removal is a safe and effective method for pediatric ureteral stone less than 10 mm in diameter.

Antegrade flexible ureteroscopy for bilateral ureteral stones in a patient with severe hip joint ankylosis

In the past several decades there has been a remarkable development of small-caliber, flexible ureteroscopes and various ancillary instruments for stone manipulation and retrieval. Percutaneous antegrade ureteroscopy can be substituted in select cases for retrograde ureteroscopy. We report a case of a 60-year-old man with severe ankylosis in both hip joints who was diagnosed with bilateral ureteral stones. The patient underwent antegrade flexible ureteroscopy and laser lithotripsy. This case illustrates the role of antegrade flexible ureteroscopy combined with the holmium:YAG laser as a minimally invasive, safe, and effective technique for the management of stones in a patient who cannot undergo a retrograde approach.

Effect of pulse energy, frequency and length on holmium:yttrium-aluminum-garnet laser fragmentation efficiency in non-floating artificial urinary calculi

BACKGROUND AND PURPOSE

Holmium:yttrium-aluminum-garnet (Ho:YAG) laser lithotripsy is the standard lithotrite in ureteroscopy. We investigated the influence of pulse frequency, energy and length on the fragmentation efficiency of Ho:YAG laser lithotripsy in non-floating artificial stones in vitro.

MATERIALS AND METHODS

Stone fragmentation efficiency of three different Ho:YAG laser devices were evaluated in vitro at different pulse energy (1.0 and 2.0 J) and frequency settings (5 and 10 Hz), resulting in a standardized output power of 10W, respectively. Where possible, pulse length was modified (350 vs 700 microsec). Each setting was performed with a 273 microm and a 365 microm fiber. Lithotripsy was conducted using non-repulsive stones consisting of soft stone (plaster of Paris) and hard stone composition (Fujirock type 4).

RESULTS

Our results showed an increased stone disintegration efficiency at higher pulse energy (2.0 J/5 Hz vs 1.0 J/10 Hz) independently of two fiber diameters and stone types applied in this study (P < 0.05 in 18 of 20 groups). Similarly, reduction of the pulse length from 700 to 350 microsec resulted in a higher stone disintegration (P < 0.05 in 13 of 16 groups). This effect was most prominent when applied to soft stones. Higher fiber diameter was not constantly associated with an increase in stone disintegration.

CONCLUSION

We demonstrate that an increase of pulse energy and a reduction of pulse length at a standardized output power of 10W can improve Ho:YAG laser fragmentation efficiency in vitro in nonfloating stones. These results may potentially affect clinical practice of Ho:YAG laser lithotripsy in impacted or large stones, when retropulsion is excluded.

Experience with impacted upper ureteral stones; should we abandon using semirigid ureteroscopes and pneumatic lithoclast?

Introduction

The AUA/EAU Ureteral Stones Guideline Panel reported that the stone free rate for the proximal ureteral stones is around 81% when treated by either SWL or ureteroscopy (URS).

Complication rates, most notably ureteral perforation and long-term complications of URS such as stricture formation rates, have been reduced to < 5%. Moreover, impacted ureteral calculi are more difficult to fragment with SWL because of the lack of natural expansion space for stones, this result in a situation that is better managed by ureteroscopy. The aim of this study is to assess the efficacy, safety, and complications of impacted upper ureteral stone disintegration using semirigid ureteroscopes and pneumatic lithotripsy.

Methods

We retrospectively analyzed the records of 267 consecutive patients with impacted upper ureteral stones (9–20 mm) who were treated by semirigid ureteroscopes and pneumatic disintegration. The efficacy of treatment was estimated using the stone-free rate and all treatment related complications were analyzed.

Results

Except for 24 cases where the stone migrated to the kidney, the stone was successfully treated ureteroscopically, with a low rate of minimal complications such as mild hematuria (18.4%), short term low grade fever (13.5%). Only 3 patients (1.1%) had high grade fever and none had post operative stricture.

Conclusion

The use of semirigid URS and pneumatic lithotripsy in impacted upper ureteral stones in experienced hands has very satisfactory results with minimal complications. When Holmium laser and flexible URS are not available, semirigid URS and pneumatic lithotripsy is a good alternative that shouldn't, yet, be abandoned.

Impact of irrigation systems on stone migration

PURPOSE

To evaluate forces exerted on a stone with different ureteroscopic irrigation systems that could impact stone migration during ureteroscopy.

MATERIALS AND METHODS

A 3-mm steel simulated stone was welded to a 3F stone basket. The basket wire was then backloaded into the working channel of a 4.5F Wolf semirigid ureteroscope. The basket shaft was attached to a 50 g load cell. The ureteroscope was placed in a ureteral model (14F silicon tubing). Simulated blood was dripped adjacent to the stone at 12 drops/min. Endo-irrigation devices were attached to the ureteroscope, and irrigation was applied at a rate sufficient to maintain visualization of the stone. Force on the stone was measured with the following endo-irrigation systems: Gravity (183 cm H2O); pressurized irrigation (150 mm Hg, 300 mm Hg); Kosin Technology Universal Piggyback Irrigation System (UPIS) at gravity (183 cm H2O), 150 mm Hg and 300 mm Hg; EMS Medical Peditrol Foot Pump; Cook Ureteroscopy Irrigation System; ACMI Irri-Flo Irrigation Delivery System; and Boston Scientific Single-Action-Pump System (SAPS).

RESULTS

SAP required the least number of pumps (0.35/sec) to maintain a clear endoscopic field while the Peditrol device required the most (1.88/sec). Pulse duration was longest for the ACMI (1.6 sec) and shortest for pressurized gravity and UPIS (<0.3 sec). The average total maximum impulse during a pump was significantly greater with the Cook (0.017 Ns) and ACMI (0.027 Ns) systems. On average, gravity-based systems applied the least amount of force, < or =0.0006 Ns, maximum impulse at any given time.

CONCLUSIONS

Gravity-based systems exert less force than hand-held and foot-pump devices. Of the hand-held devices, the SAP exerted the least average maximum impulse on the stone.

Comparative evaluation of Swiss LithoClast 2 and holmium:YAG laser lithotripsy for impacted upper-ureteral stones

PURPOSE

We prospectively compared the results of the Swiss LithoClast System with the holmium: yttrium-aluminum-garnet (Ho:YAG) laser for ureteral lithotripsy for management of upper ureteral stones.

MATERIALS AND METHODS

Fifty patients were randomized to two groups: LithoClast classic 2 (n = 25) and Ho:YAG laser (n = 25) between January 2005 and January 2007. Procedure selection was decided by random chit allotment. All patients who successfully had ureteral dilatation (up to 10F) were included in the study. An 8/9.8F semirigid ureteroscope was used in all procedures with LithoClast 2, and either an 8F or 7F was used in patients who underwent laser lithotripsy. Patients were analyzed for fragmentation time, stone-free rate, stone up-migration, intraoperative complications, and auxiliary procedures.

RESULTS

Average stone size was 9.63 +/- 2.46 mm2 and 10.17 +/- 2.28 mm2 with overall stone-free rates of 84% and 88% (P = 0.41), respectively, for laser and LithoClast 2 groups. Stone up-migration was 24% and 16% (P = 0.82), mean stone fragmentation time was 9.82 +/- 7.58 and 7.86 +/- 3.25 minutes (P = 0.12), and stone fragments requiring ancillary procedures were 16% and 12% (P = 0.99), respectively, in laser and LithoClast 2 groups. Postoperative hematuria (up to 72 hours) was significantly (P = 0.04) prolonged in the laser group (36%) compared with the LithoClast 2 group (8%). Three patients in the LithoClast 2 group had instrument breakage.

CONCLUSION

Both Ho:YAG laser and LithoClast 2 were equally efficient in managing ureteral stones with effective stone clearance, minimum morbidity, and reduced stone up-migration.