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Enhanced Treatment Efficiency of Holmium:YAG Laser Lithotripsy by Using PEDOT:PSS Nanofluid
Preprints and early-stage research may not have been peer reviewed yet.
Abstract
Holmium: yttrium-aluminum-garnet (Ho:YAG) laser lithotripsy has been considered the gold standard for treating urinary stones, a disease with increasing prevalence in the US in recent years. While various efforts have been made to enhance the stone ablation efficiency of Ho:YAG laser, these have primarily focused on adjusting laser source settings such as pulse energy and frequency. In this study, we introduced a novel strategy to improve the ablation efficiency of the Ho:YAG laser by incorporating nanoparticles into the fluid surrounding the stone with strong near-infrared light absorption. Experimental results of stone damage revealed an 82% increase in photothermal ablation efficiency when using a "dusting" mode of laser lithotripsy in 0.03 wt.% PEDOT:PSS solution in direct contact. The enhanced NIR absorbance of the fluid was found to promote vapor tunnel formation, facilitating increased laser energy transmission to the stone surface, and to enhance stone absorbance due to trapped fluid inside, leading to greater laser energy absorption for photothermal ablation. Furthermore, cytotoxicity tests on PEDOT:PSS solution demonstrated minimal toxicity when carefully controlling concentration and application duration. This modification of fluid absorbance for efficiency improvement presents a versatile approach compatible with previously reported laser setting modulation methods, showcasing significant potential for enhancing Ho:YAG laser lithotripsy.
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HIGHLIGHTS
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The morphology of PEDOT:PSS, including in the forms of aqueous dispersions, solid films, and hydrogels, is outlined, and the application potential of PEDOT:PSS hydrogels is described.
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Fabrication techniques for PEDOT:PSS-based devices are introduced, including coating, printing, conventional lithography, and soft lithography.
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The latest developments in four main categories of PEDOT:PSS-based physical sensors, for humidity, temperature, pressure, and strain, respectively, are introduced.
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The development prospects for PEDOT:PSS, from materials to fabrication techniques to physical sensors, are outlined.
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.
We study a conductive polymer PEDOT: PSS for infrared thermal detection. We propose to use PEDOT: PSS simultaneously as the thermal sensitive material, infrared absorption layer, thermal insulation layer, as well as the electrical connection material. We demonstrate theoretically and confirm experimentally that PEDOT: PSS has a high temperature coefficient of resistance (TCR) of ∼0.6%/K at room temperature, which is comparable to those inorganic materials commonly used in commercial bolometers. We then experimentally characterize the infrared absorption of a thin PEDOT: PSS film, and we find that it has considerable absorption (over 0.2) in a broad range even with a film as thin as 100nm. This is beneficial to reduce the thermal capacitance and thereby increase the response speed. Finally, we characterize the infrared response of PEDOT: PSS film, and the detectivity is found to be 2×10⁸ cmHz1/2/W. This work is especially inspirational in the design and fabrication of versatile, and highly integrated sensors and detectors, as well as other polymer-based devices and systems.
The flashlamp-pumped, solid-state, pulsed, mid-infrared, holmium:YAG laser (λ = 2120 nm) has been the clinical gold standard laser for lithotripsy for over the past two decades. However, while the holmium laser is the dominant laser technology in ureteroscopy because it efficiently ablates all urinary stone types, this mature laser technology has several fundamental limitations. Alternative, mid-IR laser technologies, including a thulium fiber laser (λ = 1908 and 1940 nm), a thulium:YAG laser (λ = 2010 nm), and an erbium:YAG laser (λ = 2940 nm) have also been explored for lithotripsy. The capabilities and limitations of these mid-IR lasers are reviewed in the context of the quest for an ideal laser lithotripsy system capable of providing both rapid and safe ablation of urinary stones.
Purpose of review:
Laser lithotripsy is increasingly used worldwide and is a continuously evolving field with new and extensive research being published every year.
Recent findings:
Variable pulse length Ho:YAG lithotripters allow new lithotripsy parameters to be manipulated, and there is an effort to integrate new technologies into lithotripters. Pulsed thulium lasers seem to be a viable alternative to holmium lasers. The performance of similar laser fibers varies from manufacturer to manufacturer. Special laser fibers and "cleaving only" fiber tip preparation can be beneficial for the lithotripsy procedure. Different laser settings and the surgical technique employed can have significant impact on the success of laser lithotripsy. When safely done, complications of laser lithotripsy are rare and concern the endoscopic nature of procedure, not the technology itself, making laser lithotripsy one of the safest tools in urology. Laser lithotripsy has had several new developments and more insight has been gained in recent years with many more advances expected in the future.
Purpose:
To evaluate the thermal effect of Ho:YAG laser lithotripsy in a standardized in vitro model via real-time temperature measurement.
Methods:
Our model comprised a 20 ml test tube simulating the renal pelvis that was immersed in a 37 °C water bath. Two different laser fibers [FlexiFib (15-45 W), RigiFib 1000 (45-100 W), LISA laser products OHG, Katlenburg-Lindau, Germany] were placed in the test tube. An Ho:YAG 100 W laser was used in all experiments (LISA). Each experiment involved 120 s of continuous laser application, and was repeated five times. Different laser settings (high vs. low frequency, high vs. low energy, and long vs. short pulse duration), irrigation rates (0 up to 100 ml/min, realized by several pumps), and human calcium oxalate stone samples were analyzed. Temperature data were acquired by a real-time data logger with thermocouples (PICO Technology, Cambridgeshire, UK). Real-time measurements were assessed using MatLab®.
Results:
Laser application with no irrigation results in a rapid increase in temperature up to ∆28 K, rising to 68 °C at 100 W. Low irrigation rates yield significantly higher temperature outcomes. Higher irrigation rates result immediately in a lower temperature rise. High irrigation rates of 100 ml/min result in a temperature rise of 5 K at the highest laser power setting (100 W).
Conclusions:
Ho:YAG laser lithotripsy might be safe provided that there is sufficient irrigation. However, high power and low irrigation resulted in potentially tissue-damaging temperatures. Laser devices should, therefore, always be applied in conjunction with continuous, closely monitored irrigation whenever performing Ho:YAG laser lithotripsy.
Objective:
To evaluate in vitro and in vivo effects of Moses technology in Holmium laser and to compare it with the Regular mode in terms of lithotripsy efficiency and laser-tissue interactions.
Methods:
The Lumenis? PulseTM P120H holmium laser system together with Moses D/F/L fibers were used to compare Regular mode with the Moses modes in stone retropulsion using a high-speed camera, and stone ablation efficiency. In addition, a porcine ureteroscopy model was used to assess stone fragmentation and dusting as well as laser-tissue interaction with the ureteral wall.
Results:
Following a laser pulse, in vitro stone displacement experiments showed significant reduction in retropulsion when using the Moses modes. The stone movement was reduced by 50 times at 0.8J and 10Hz (p<0.01). The pronounced reduction of retropulsion in the Moses modes was clearly observed during fragmentation setting (high energy) and dusting (low energy, high Hz). In addition, stone fragmentation tests showed that the Moses modes resulted in significantly higher ablation volume when compared with Regular mode (160% higher; p<0.001). In vivo assessment also supported the reduction in retropulsion when treating stones in the porcine kidney. Histological analysis of the porcine ureter after direct lasing in the Moses modes suggested less damage than in the Regular mode.
Conclusions:
The Moses technology resulted in more efficient laser lithotripsy in addition to significantly reduced stone retropulsion and displayed a margin of safety that may result in shorter procedural time and safer lithotripsy.
Objectives:
In vitro investigations of Ho:YAG laser-induced stone fragmentation were performed to identify potential impacts of different pulse durations on stone fragmentation characteristics.
Materials and methods:
A Ho:YAG laser system (Swiss LaserClast, EMS S.A., Nyon, Switzerland) with selectable long or short pulse mode was tested with regard to its fragmentation and laser hardware compatibility properties. The pulse duration is depending on the specific laser parameters. Fragmentation tests (hand-held, hands-free, single-pulse-induced crater) on artificial BEGO stones were performed under reproducible experimental conditions (fibre sizes: 365 and 200 µm; laser settings: 10 W through combinations of 0.5, 1, 2 J/pulse and 20, 10, 5 Hz, respectively).
Results:
Differences in fragmentation rates between the two pulse duration regimes were detected with statistical significance for defined settings. Hand-held and motivated Ho:YAG laser-assisted fragmentation of BEGO stones showed no significant difference between short pulse mode and long pulse mode, neither in fragmentation rates nor in number of fragments and fragment sizes. Similarly, the results of the hands-free fragmentation tests (with and without anti-repulsion device) showed no statistical differences between long pulse and short pulse modes.
Conclusion:
The study showed that fragmentation rates for long and short pulse durations at identical power settings remain at a comparable level. Longer holmium laser pulse duration reduces stone pushback. Therefore, longer laser pulses may result in better clinical outcome of laser lithotripsy and more convenient handling during clinical use without compromising fragmentation effectiveness.
Characteristics of thermo-mechanical laser ablation process are investigated using an original numerical model. In contrast
with previous models, it is based on a microscopic physical model of the micro-explosion process, which combines thermodynamic
behavior of tissue water with elastic response of the solid tissue components. Diffusion of dissipated heat is treated in
one dimension, and the amount of thermal damage is assessed using the Arrhenius model of the protein denaturation kinetics.
Influence of the pulse fluence and duration on temperature profile development, ablation threshold, and depth of thermal damage
is analyzed for the case of Er:YAG laser irradiation of human skin. Influence of mechanical properties on the ablation threshold
of soft tissue is predicted theoretically for the first time. In addition, feasibility of deep tissue coagulation with a repetitively
pulsed Er:YAG laser is indicated from the model.
Surfactants reduce vapor bubble surface tension and increase bubble dimensions, which may potentially enable longer non-contact working distances during laser lithotripsy and/or lower laser energy for creating bubbles. This study compares vapor bubble characteristics of two commercially available surfactants over a wide range of concentrations and laser parameters. A Thulium fiber laser (TFL) at 1940 nm delivered single laser pulses through 200-μm-core fibers with 0.22 numerical aperture, in a 9.5 L water tank. The TFL was operated with four laser settings, at constant peak power of 200 W (50 mJ / 250 μs; 100 mJ / 500 μs; 200 mJ / 1000 μs; 500 mJ / 2500 μs). Two surfactants (Tween 20 and 80) were tested with concentrations of 0% - water (control), 0.1%, 1%, and 10%. A total of ninety-two experiments were conducted: (2 surfactants x 3 concentrations x 4 parameters x 3 tests) + 20 tests in water). A highspeed camera operating at 200,000 frames per second and with 256 x 160 resolution, imaged bubble dimensions. ImageJ and MATLAB software were used to analyze bubble dimensions. A 1% concentration of Tween 20 provided optimal results, balancing increased bubble dimensions with solubility and visibility. At 1%, Tween 20 produced 5.3% and 8.0% greater bubble lengths than Tween 80 and water, respectively, and 5.4% greater bubble width than water. Bubble lifetime increased with increasing surfactant concentration, and the number of bubbles in a laser pulse also increased with laser pulse energy and pulse duration for all parameters tested. Tween 20 yields longer bubble lengths than water and Tween 80, for potential use as an irrigant during laser lithotripsy.
Objective:
To investigate the mechanism of stone dusting in Holmium (Ho): YAG laser lithotripsy (LL).
Materials and methods:
Cylindrical BegoStone samples (6 x 6 mm, H x D) were treated in water using a clinical Ho: YAG laser lithotripter in dusting mode (0.2 ~ 0.4 J with 70 ~ 78 s in pulse duration, 20 Hz) at various fiber tip to stone standoff distances (SD = 0, 0.5, and 1 mm). Stone damage craters were quantified by optical coherence tomography and bubble dynamics were captured by high-speed video imaging. To differentiate the contribution of cavitation vs. thermal ablation to stone damage, three additional experiments were performed. First, pre-soaked wet stones were treated in air to assess stone damage without cavitation. Second, the laser fiber was advanced at various offset distances (OSD = 0.25, 1, 2, 3, and 10 mm) from the tip of a flexible ureteroscope to alter the dynamics of bubble collapse. Third, stones were treated with parallel fiber to minimize photothermal damage while isolating the contribution of cavitation to stone damage.
Results:
Treatment in water resulted in 2.5- to 90-fold increase in stone damage compared to those produced in air where thermal ablation dominates. With the fiber tip placed at OSD = 0.25 mm, the collapse of the bubble was distracted away from the stone surface by the ureteroscope tip, leading to significantly reduced stone damage compared to treatment without the scope or with scope at large OSD of 3 ~ 10 mm. The average crater volume produced by parallel fiber orientation at 0.2 J after 100 pulses where cavitation is the dominant mechanism of stone damage was comparable with those produced by using perpendicular fiber orientation within SD = 0.25 ~ 1 mm.
Conclusion:
Cavitation plays a dominant role over photothermal ablation in stone dusting during short pulse Ho: YAG LL.
Purpose:
While cavitation during laser lithotripsy contributes to the Moses effect, the impact of cavitation on stone damage is less clear. Using different laser settings, we investigate the role of cavitation bubbles in energy delivery and stone damage.
Materials and methods:
The role of cavitation in laser energy delivery was characterized using photodetector measurements synced with high-speed imaging for laser pulses of varying durations. BegoStone samples were treated with the laser fiber oriented perpendicularly in contact with the stone in water or in air to assess the impact of cavitation on crater formation. Crater volume and geometry were quantified using optical coherence tomography. Furthermore, the role of cavitation in stone damage was elucidated by treatment in water with the fiber oriented parallel to the stone surface and by photoelastic imaging.
Results:
Longer pulse durations resulted in higher energy delivery but smaller craters. Stones treated in water resulted in greater volume, wider yet shallower craters compared to those treated in air. Stones treated with the parallel fiber showed crater formation after 15 pulses, confirmed by high-speed imaging of the bubble collapse with the resultant stress field captured by photoelastic imaging.
Conclusions:
Despite improved energy delivery, the longer pulse mode produced smaller crater volume, suggesting additional processes secondary to photothermal ablation are involved in stone damage. Our critical observations of the difference in stone damage treated in water vs. in air, combined with the crater formation by parallel fiber suggest that cavitation is a contributor to stone damage during laser lithotripsy.
With the development of flexible electronic devices such as organic electrodes, medical sensors and light-emitting diodes, conductive polymer: poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) has attracted tremendous research attention due to its unique...
Kidney stones are a common disorder, with an annual incidence of eight cases per 1,000 adults. During an episode of renal colic, the first priority is to rule out conditions requiring immediate referral to an emergency department, then to alleviate pain, preferably with a nonsteroidal anti-inflammatory drug. The diagnostic workup consists of urinalysis, urine culture, and imaging to confirm the diagnosis and assess for conditions requiring active stone removal, such as urinary infection or a stone larger than 10 mm. Conservative management consists of pain control, medical expulsive therapy with an alpha blocker, and follow-up imaging within 14 days to monitor stone position and assess for hydronephrosis. Asymptomatic kidney stones should be followed with serial imaging, and should be removed in case of growth, symptoms, urinary obstruction, recurrent infections, or lack of access to health care. All patients with kidney stones should be screened for risk of stone recurrence with medical history, basic laboratory evaluation, and imaging. Lifestyle modifications such as increased fluid intake should be recommended for all patients, and thiazide diuretics, allopurinol, or citrates should be prescribed for patients with recurrent calcium stones. Patients at high risk of stone recurrence should be referred for additional metabolic assessment, which can serve as a basis for tailored preventive measures.
Electronic structure and optical absorption spectra of poly(3,4-ethylenedioxythiophene) (PEDOT) for different oxidation levels were studied using density functional theory (DFT) and time-dependent DFT. It is shown that the DFT-based predictions for the polaronic and bipolaronic states and the nature of corresponding optical transitions are qualitatively different from the widely used traditional picture based on semi-empirical pre-DFT approaches that still dominate the current literature. Based on the results of our calculations, the experimental Vis/NIR absorbance spectroscopy and the electron paramagnetic resonance spectroscopy are re-examined and a new interpretation of the measured spectra and the spin signal which is qualitatively different from the traditional interpretation is provided. The findings and conclusions concerning the nature of polaronic and bipolaronic states, band structure and absorption spectra presented for PEDOT, are generic for a wide class of conducting polymers (such as polythiophenes and their derivatives) that have similar structure of monomer units.
Objectives:
The aim of this study was to investigate "calyceal" fluid temperature changes during holmium laser activation/lithotripsy using settings up to 40 watt power output with different irrigation flow rates.
Methods:
The experimental system consisted of a glass test tube (diameter 10 mm/length 75 mm) filled with deionized water, to mimic a calyx. Real time temperature was recorded using a thermocouple (Physitemp, NJ) positioned 5 mm from the bottom of the tube. A 200 µm laser fiber (Flexiva, Boston Scientific, MA) was introduced through the working channel of a disposable ureteroscope (Lithovue,Boston Scientific, MA) and the laser fiber tip was positioned 15 mm above the bottom of the test tube. Deionized water irrigation (room temperature) through the working channel of the ureteroscope was delivered at flow rates of 0, 7-8, 14-15, and 38-40 ml/min. A 120-watt holmium laser (Pulse 120, Lumenis, CA) was used. The following settings were explored: 0.5J x 10Hz, 1.0J x 10Hz, 0.5J x 20Hz, 1.0J x 20Hz, 0.5J x 40Hz, 1.0J x 40Hz, and 0.5J x 80Hz. During each experiment the laser was activated continuously for 60 seconds.
Results:
Temperature increased with increasing laser power output and decreasing irrigation flow rate. The highest temperature, 70.3°C (SD 2.7) occurred with laser setting of 1.0J x 40Hz and no irrigation after 60 seconds of continuous laser firing. None of the tested laser settings and irrigation parameters produced temperature exceeding 51°C when activated for only 10 seconds of continuous laser firing.
Conclusion:
High power holmium settings fired in long bursts with low irrigation flow rates can generate high fluid temperatures in a laboratory 'calyceal' model. Awareness of this risk, allows urologist to implement a variety of techniques (higher irrigation flow rates, intermittent laser activation, and potentially cooled irrigation fluid) to control and mitigate thermal effects during holmium laser lithotripsy.
Electrohydraulic lithotripsy was used to manage 45 upper tract calculi (23 renal and 22 ureteral stones) in 40 patients. Electrohydraulic lithotripsy successfully fragmented 91% of the calculi. All ureteral fragments cleared; in 2 patients with renal calculi solitary 4 mm. stone fragments remained. There were no intraoperative or long-term complications directly related to the use of electrohydraulic lithotripsy in the upper urinary tract. We conclude that intrarenal and intraureteral electrohydraulic lithotripsy is a safe, effective, inexpensive means to perform intracorporeal lithotripsy. (J. Urol, 143: 13–17, 1990)
Conductive polymer consisting of poly(3,4-ethylenedioxythiophene)/cross-linked poly(p-styrenesulfonate) (PEDOT/CL-PSS) particles was synthesized, and its dispersion and film properties were evaluated. CL-PSS was synthesized by sulfonation of poly(styrene-co-divinylbenzene) prepared by emulsion polymerization, and PEDOT/CL-PSS was synthesized by oxidative polymerization of EDOT in the presence of CL-PSS particles. The dispersion of PEDOT/CL-PSS exhibited lower viscosity than that of the usual PEDOT/PSS, enabling the highly concentrated dispersion of the conductive polymer in water. The electrostabilities of the PEDOT/CL-PSS film against heat and humidity were significantly improved by the cross-linkage, although the conductivity decreased with the increase of crosslink density. PEDOT/CL-PSS was miscible with PEDOT/PSS and could be used as a surface roughness-controlling agent for PEDOT/PSS film.
Kidney stones have been rising in prevalence in the United States and worldwide, and represent a significant cost burden. Cost effectiveness research in this area may enable improvements in treatment efficiency that can benefit patients, providers and the healthcare system. There has been limited research in the cost effectiveness of surgical interventions for stone disease, despite the diverse treatment approaches that are available. Medical expulsive therapy (MET) has been shown to improve rates of stone passage for ureteral stones, and there is evidence that this practice should be liberalized from the standpoint of both clinical and cost effectiveness. While conservative treatment following a primary stone event appears to be cost effective, the economic impact of medical therapy for recurrent stone formers requires clarification despite its clinical efficacy. Future study regarding the cost effectiveness of prevention and interventions for stone disease are likely to improve both the quality and efficiency of care.
Context:
Management of urinary stones is a major issue for most urologists. Treatment modalities are minimally invasive and include extracorporeal shockwave lithotripsy (SWL), ureteroscopy (URS), and percutaneous nephrolithotomy (PNL). Technological advances and changing treatment patterns have had an impact on current treatment recommendations, which have clearly shifted towards endourologic procedures. These guidelines describe recent recommendations on treatment indications and the choice of modality for ureteral and renal calculi.
Objective:
To evaluate the optimal measures for treatment of urinary stone disease.
Evidence acquisition:
Several databases were searched to identify studies on interventional treatment of urolithiasis, with special attention to the level of evidence.
Evidence synthesis:
Treatment decisions are made individually according to stone size, location, and (if known) composition, as well as patient preference and local expertise. Treatment recommendations have shifted to endourologic procedures such as URS and PNL, and SWL has lost its place as the first-line modality for many indications despite its proven efficacy. Open and laparoscopic techniques are restricted to limited indications. Best clinical practice standards have been established for all treatments, making all options minimally invasive with low complication rates.
Conclusion:
Active treatment of urolithiasis is currently a minimally invasive intervention, with preference for endourologic techniques.
Patient summary:
For active removal of stones from the kidney or ureter, technological advances have made it possible to use less invasive surgical techniques. These interventions are safe and are generally associated with shorter recovery times and less discomfort for the patient.
To assess the fragmentation (ablation) efficiency of laser lithotripsy along a wide range of pulse energies, frequencies, power settings and different laser fibres, paying special attention to compare high frequency to low frequency lithotripsy using a dynamic and innovative testing procedure free from any human interaction bias.
An automated laser fragmentation testing system was developed. The unmoving laser fibres fire at the surface of an artificial stone while the stone is moved past at a constant velocity, thus creating a fissure. The lithotripter settings were 0.2 - 1.2 J pulse energies, 5 - 40 Hz frequencies, 4 - 20 W power levels, and 200 and 550 μm core laser fibres. Fissure width, depth, and volume were analysed and comparisons between laser settings, fibres and ablation rates were made.
Low frequency-high pulse energy (LoFr-HiPE) settings were (up to six times) more efficient than high frequency-low pulse energy (HiFr-LoPE) at the same power levels (p < 0.00001) as they produced deeper (p < 0.01) and wider (p < 0.00001) fissures. There were linear correlations between pulse energy and fragmentation volume, fissure width, and fissure depth (all p < 0.00001). Total power did not correlate with fragmentation measurements. Laser fibre diameter did not affect fragmentation volume (p = 0.81), except at very low pulse energies (0.2 J), where the large fibre was less efficient (p = 0.015).
At the same total power level, LoFr-HiPE lithotripsy was most efficient. Pulse energy was the key variable that drove fragmentation efficacy. Attention must be paid to prevent the formation of time-consuming bulky debris and adapt the lithotripter settings to one's needs. Since fibre diameter did not affect fragmentation efficiency, small fibres are preferable due to better scope irrigation and manoeuvrability.
The influence of anode buffer layers of doped poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) on the performance of solar cells made from blends of poly(3-hexylthiophene) and [6,6]-phenyl-C61-buytyric acid methyl ester has been investigated. Different concentration of ethylene glycol were added into the PEDOT:PSS solution to increase its conductivity. The surface roughness of the doped PEDOT:PSS film was changed, which was examined by atomic force microscopy. The best doped device with a power conversion efficiency of 4.39% as compared to 3.41% for the pristine device has been achieved. The enhanced PEDOT:PSS conductivity improved the short circuit current and fill factor of the doped device. The almost constant open circuit voltage indicated the well-established ohmic contact between the anode and active layer irrespective of the doping of the PEDOT:PSS. The changed surface roughness of the doped PEDOT:PSS film did not correlate with the morphology of the consequent active layer and the resultant device performance.
The last nationally representative assessment of kidney stone prevalence in the United States occurred in 1994. After a 13-yr hiatus, the National Health and Nutrition Examination Survey (NHANES) reinitiated data collection regarding kidney stone history.
Describe the current prevalence of stone disease in the United States, and identify factors associated with a history of kidney stones.
A cross-sectional analysis of responses to the 2007-2010 NHANES (n=12 110). OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Self-reported history of kidney stones. Percent prevalence was calculated and multivariable models were used to identify factors associated with a history of kidney stones.
The prevalence of kidney stones was 8.8% (95% confidence interval [CI], 8.1-9.5). Among men, the prevalence of stones was 10.6% (95% CI, 9.4-11.9), compared with 7.1% (95% CI, 6.4-7.8) among women. Kidney stones were more common among obese than normal-weight individuals (11.2% [95% CI, 10.0-12.3] compared with 6.1% [95% CI, 4.8-7.4], respectively; p<0.001). Black, non-Hispanic and Hispanic individuals were less likely to report a history of stone disease than were white, non-Hispanic individuals (black, non-Hispanic: odds ratio [OR]: 0.37 [95% CI, 0.28-0.49], p<0.001; Hispanic: OR: 0.60 [95% CI, 0.49-0.73], p<0.001). Obesity and diabetes were strongly associated with a history of kidney stones in multivariable models. The cross-sectional survey design limits causal inference regarding potential risk factors for kidney stones.
Kidney stones affect approximately 1 in 11 people in the United States. These data represent a marked increase in stone disease compared with the NHANES III cohort, particularly in black, non-Hispanic and Hispanic individuals. Diet and lifestyle factors likely play an important role in the changing epidemiology of kidney stones.
Purpose:
Due to the unavailability of suitable pediatric instruments children have not benefited from advances in endoscopic lithotripsy. This limitation may be overcome by the holmium: YAG laser. We evaluated the indications for, and efficacy and complications of holmium:YAG laser lithotripsy.
Materials and methods:
We retrospectively reviewed all cases of laser lithotripsy. Access to the calculus was antegrade or retrograde. A solid state holmium:YAG laser was used.
Results:
Eight patients 4 to 14 years old underwent laser lithotripsy during the study period. Average calculous surface area was 357.13 mm.2 (range 14 to 1,645). Five patients required 1 procedure to render them stone-free, while the remaining 3 required multiple procedures. No complications were associated with laser lithotripsy.
Conclusions:
The ability of the holmium:YAG laser to pulverize urinary calculi makes it an alternative choice for lithotripsy. In our series all patients are stone-free with stable renal function. The advantages of the holmium:YAG laser are that it may be precisely applied via small fibers, and it pulverizes calculi with minimal scattering of energy and retropulsion of the calculus, decreasing trauma to tissues at the perioperative site. There is also a lower risk of residual fragments, which is associated with a lower incidence of calculous regrowth. Holmium: YAG laser is safe and effective for treating pediatric urolithiasis.
Laser lithotripsy is one possibility for an intracorporeal lithotripsy. Different pulsed lasers are used for this purpose. They differ in their wavelength, pulse duration and pulse energy. Therefore the fragmentation process is slightly – in case of the Ho:YAG-laser strongly – different. Nevertheless the ability of stone fragmentation is comparable. Therefore safety aspects, reliability and costs are an important criterion for the choice. The fragmentation can be divided in a succession of processes: plasma formation, plasma expansion with generation of a shockwave and cavitation oscillation. Whereas the primary shockwave and the cavitation collapse are the origin of mechanical effects causing fragmentation. The Ho:YAG-laser due to its long pulse length and high pulse energy shows mainly thermal effects.
The holmium:YAG (Ho:YAG) laser lithotriptor is capable of operating at high pulse energies, but efficient operation is limited to low pulse rates (∼10 Hz) during lithotripsy. On the contrary, the thulium fiber laser (TFL) is limited to low pulse energies, but can operate efficiently at high pulse rates (up to 1000 Hz). This study compares stone ablation threshold, ablation rate, and retropulsion for the two different Ho:YAG and TFL operation modes. The TFL (λ = 1908 nm) was operated with pulse energies of 5 to 35 mJ, 500-μs pulse duration, and pulse rates of 10 to 400 Hz. The Ho:YAG laser (λ = 2120 nm) was operated with pulse energies of 30 to 550 mJ, 350-μs pulse duration, and a pulse rate of 10 Hz. Laser energy was delivered through 200- and 270-μm-core optical fibers in contact mode with human calcium oxalate monohydrate (COM) stones for ablation studies and plaster-of-Paris stone phantoms for retropulsion studies. The COM stone ablation threshold for Ho:YAG and TFL measured 82.6 and 20.8 J∕cm(2), respectively. Stone retropulsion with the Ho:YAG laser linearly increased with pulse energy. Retropulsion with TFL was minimal at pulse rates less than 150 Hz, then rapidly increased at higher pulse rates. For minimal stone retropulsion, Ho:YAG operation at pulse energies less than 175 mJ at 10 Hz and TFL operation at 35 mJ at 100 Hz is recommended, with both lasers producing comparable ablation rates. Further development of a TFL operating with both high pulse energies of 100 to 200 mJ and high pulse rates of 100 to 150 Hz may also provide an alternative to the Ho:YAG laser for higher ablation rates, when retropulsion is not a primary concern.
Purpose:
Management of large impacted upper ureteral calculi remains challenging for urologists. These calculi are frequently associated with obstructive uropathy and deteriorated renal function. Extracorporeal shock wave lithotripsy (SWL) is the least invasive treatment but its success rate is decreased for large impacted upper ureteral calculi. According to the American Urological Association guidelines on ureteral stones published in 1997, the appropriateness of ureteroscopy decreases when stone size exceeds 1 cm. However, the application of advanced ureteroscopy and techniques has increased the success rate of treating proximal ureter calculi. In this study we compared the safety and efficacy of ureterorenoscopic holmium:YAG laser lithotripsy (URSL) with SWL for large impacted proximal ureteral stones.
Materials and methods:
This study evaluated 82 patients with large impacted upper ureteral stones. Two patients were excluded from study owing to conversion to open surgery. SWL and URSL were performed in 41 and 39 patients, respectively. Those in the SWL group were treated on an outpatient basis with Medispec Econolith 2000 (Medispec, Germantown, Maryland) under intravenous sedation. The URSL was performed with a 6/7.5Fr semirigid tapered ureterorenoscope and holmium:YAG laser with the patient under spinal anesthesia on an inpatient basis. Successful outcome was defined as the patient being stone-free on radiography 1 month after treatment. Stone size, success rate, postoperative complications and cost were analyzed in each group.
Results:
A total of 80 patients were enrolled in this study. Hematuria and flank pain were the most common complaints in each group. Mean stone size +/- SD was 1.28 +/- 0.04 cm in the SWL group and 1.51 +/- 0.05 cm in URSL group (p = 0.0009). Accessibility of the semirigid ureterorenoscope for impacted upper ureteral stones was 95.1% (39 of 41) and the stone-free rate achieved after 1 sitting was 92% (36 of 39). The initial stone-free rate of in situ SWL was 61% (25 of 41). Notably, the initial stone-free rate in the URSL group was better than that of the SWL group (p = 0.003). The efficiency quotient was 0.53 for URSL and 0.59 for SWL. The average cost in the URSL group appears to be lower than in the SWL group. Both groups were free of major complications.
Conclusions:
This study demonstrated that URSL achieved excellent results for upper ureteral calculi greater than 1 cm. Thus, this procedure should be considered first line therapy for large proximal ureteral stones.
The tissue effects of a holmium:YAG (Ho:YAG) laser operating at a wavelength of 2.1 mu with a maximum power of 15 watts (W) and 10 different energy-pulse settings was systematically evaluated on kidney, bladder, prostate, ureteral, and vasal tissue in the dog. In addition, various urologic surgical procedures (partial nephrectomy, transurethral laser incision of the prostate, and laser-assisted vasovasostomy) were performed in the dog, and a laparoscopic pelvic lymph node dissection was carried out in a pig. Although the Ho:YAG laser has a strong affinity for water, precise tissue ablation was achieved in both the contact and non-contact mode when used endoscopically in a fluid medium to ablate prostatic and vesical tissue. Using the usual parameters for tissue destruction (blanching without charring), the depth of thermal injury in the bladder and ureter was kept superficial. In performing partial nephrectomies, a 2-fold reduction in the zone of coagulative necrosis was demonstrated compared to the use of the continuous wave Neodymium:YAG laser (Nd:YAG). When used through the laparoscope, the Ho:YAG laser provided precise cutting and, combined with electrocautery, allowed the dissection to proceed quickly and smoothly. Hemostatic control was adequate in all surgical procedures. Although the results of these investigations are preliminary, our initial experience with the Ho:YAG laser has been favorable and warrants further investigations.
Four new technologies have transformed the treatment of urinary calculi: electrohydraulic lithotripsy, ultrasonic lithotripsy, extracorporeal shock wave lithotripsy, and laser lithotripsy. Initial attempts to ablate urinary calculi by continuous wave CO2, ruby, and Nd-YAG lasers failed because of excess thermal injury and inability to pass the laser energy via a flexible fiber. Basic laboratory studies then demonstrated that short pulsed laser energy absorbed by the calculus resulted in fragmentation. The parameters that produced optimal urinary calculus fragmentation were found using the flashlamp pumped tunable dye laser, with the following parameters: wavelength: 504 nm; pulse duration: 1 microsec; fiber: 250 micro silica-coated quartz; repetition: 5-20 Hz. Use of pulsed dye laser caused no tissue damage. The mechanism of fragmentation is light absorption, plasma development, and repetitive acoustic shock wave action with resultant fragmentation. The techniques for application of laser to calculi have been successful, and new, miniature instruments have been developed. Laser lithotripsy is a successful method for fragmenting ureteral calculi. The small caliber of the laser fiber makes this method useful for treating calculi in narrow, tortuous ureters; impacted calculi; distal calculi in ureters that cannot be dilated, via the percutaneous route for stones in calyces or impacted in the upper ureter. Investigations are continuing to optimize fragmentation of harder calculi and to use laser fragmentation within the kidney. Laser lithotripsy may also be used to fragment biliary calculi.
With the increasing range of indications for extracorporeal shock-wave lithotripsy, "easy" cases of ureteroscopic stone removal have vanished. Clinical experience with ureterolitholapaxy has proved the method safe, effective, and reliable in the hands of the experienced urologist.
Extracorporeal shock wave lithotripsy (ESWL) is considered standard therapy for most renal calculi as well as more than 80% of all upper urinary tract stones. The development of flexible and small diameter rigid ureteroscopes, and the increased availability of laser lithotriptors have made endoscopic treatment of ureteral calculi more successful and safe. This report represents our contemporary series of 80 single mid and proximal ureteral calculi treated endoscopically.
A total of 78 patients underwent 80 primary endoscopic procedures with 3 auxiliary ESWL and 2 endoscopic re-treatments for 41 mid and 39 proximal ureteral calculi. Lithotripsy was performed for 55 of the 80 stones.
Of the 80 stones 75 (94%) successfully cleared 1 month after 1 endoscopic procedure. The success rate was 38 of 39 (97%) for proximal calculi and 37 of 41 (90%) for mid ureteral stones. With a single re-treatment overall success increased to 96%. If adjuvant ESWL was added, 100% success was attained. Currently all procedures are performed on an outpatient basis. Morbidity is low and there have been no major complications, such as stricture, renal loss or death.
Our series demonstrates the high success rate that can be achieved with ureteroscopic removal of mid and proximal ureteral calculi. Thus, ureteroscopic treatment should be considered a treatment of choice for upper ureteral calculi.
To investigate the safety and efficacy of electrokinetic lithotripsy (EKL), a ballistic lithotripter which uses high-energy magnetic fields to propel an impactor to fragment calculi.
The records and radiographs of 121 patients who underwent ureteroscopy using the EKL for stones in the upper (26), mid (28) or lower (67) ureter were reviewed retrospectively. Ureteroscopy was performed with an 8.5 F semi-rigid ureteroscope, through which a 3 F EKL probe was passed.
A total of 148 stones (mean stone size 11.5 mm, range 6-40) in 121 patients were treated using the EKL. One patient was lost to follow-up. Of 148 stones, 147 (99.3%) were fragmented, including five that had resisted fragmentation with either pulsed-dye laser or electrohydraulic lithotripsy. Despite this, only 45 of 56 patients (80%) with a single stone in the lower ureter were rendered stone-free after a single ureteroscopic procedure. Seven patients in this group (12%) required shock-wave lithotripsy for fragments that had been propelled into the kidney, while four patients (7%) required repeat ureteroscopy for retained ureteric fragments. Complications were limited to minor ureteric perforations in two patients, both of which were treated with a stent.
EKL is an inexpensive and reliable endoscopic method which fragments nearly all urinary calculi. Its limitations include the propulsion of fragments and the need to use an offset, semi-rigid ureteroscope. We recommend the use of a basket or graspers to remove fragments of >/=4 mm after EKL.
We determined the safety and efficacy of holmium:YAG lithotripsy in children.
We retrospectively reviewed the records of all holmium:YAG lithotripsy done in patients 17 years old or younger. Demographic, preoperative, intraoperative and postoperative data were collected.
A total of 9 boys and 10 girls (26 stones) with a mean age of 11 years (range 1 to 17) were treated with holmium:YAG lithotripsy, which was chosen as initial therapy in 10 (53%). Retrograde ureteroscopy was performed in 15 patients to treat 13 ureteral and 6 renal calculi, and percutaneous nephrolithotripsy was done in 4 to treat 3 ureteral and 4 renal calculi. A complete stone-free outcome after 1 procedure was achieved in 16 children (84%) and 3 patients were rendered stone-free after 2 procedures. No patient had an intraoperative injury. Followup ranged from 0.5 to 12 months (mean 3). Followup imaging has shown no evidence of stricture or hydronephrosis.
Holmium:YAG lithotripsy is safe and effective in children. It is a reasonable option for failed shock wave lithotripsy, or in children with a known durile stone composition or contraindications to shock wave lithotripsy.
To review the results of holmium laser lithotripsy in a cohort of patients who presented with symptomatic urolithiasis in pregnancy. Symptomatic urolithiasis in pregnancy that does not respond to conservative measures has traditionally been managed with ureteral stent insertion or percutaneous nephrostomy. Holmium:yttrium-aluminum-garnet (YAG) laser lithotripsy using state-of-the-art ureteroscopes represents an emerging strategy for definitive stone management in pregnancy.
A retrospective analysis was conducted at two tertiary stone centers from January 1996 to August 2001 to identify pregnant patients who were treated with ureteroscopic holmium laser lithotripsy for symptomatic urolithiasis or encrusted stents. Eight patients with a total of 10 symptomatic ureteral calculi and two encrusted ureteral stents were treated. The mean gestational age at presentation was 22 weeks. The mean stone size was 8.1 mm. The stones were located in the proximal ureter/ureteropelvic junction (n = 3), midureter (n = 1), and distal ureter (n = 6).
Complete stone fragmentation and/or removal of encrusted ureteral stents were achieved in all patients using the holmium:YAG laser. The overall procedural success rate was 91%. The overall stone-free rate was 89%. No obstetric or urologic complications were encountered.
Ureteroscopy and holmium laser lithotripsy can be performed safely in all stages of pregnancy, providing definitive management of symptomatic ureteral calculi. The procedure can be done with minimal or no fluoroscopy and avoids the undesirable features of stents or nephrostomy tubes.
To evaluate the results of pneumatic lithotripsy (PL) with ureteroscopy in the treatment of ureteral stones.
We reviewed, retrospectively, the records of 500 patients (366 male, 134 female) with ureteral calculi treated by PL with the Swiss Lithoclast. Of these patients, 124 (24.8%) were treated primarily and 376 (75.2%) were treated secondarily after unsuccessful extracorporeal shockwave lithotripsy (SWL). The results were evaluated 3 months after treatment by excretory urography, ultrasonography, or both.
The over-all stone-free and fragmentation rates were 94.6% and 96.8%, respectively. These values were 97.1% and 98.5% for stones <or=10 mm and 83.7% and 89.1% for stones >10 mm, respectively. The main complications were stone migration (2.0%), urosepsis (3.0%), and ureteral perforation (1.4%).
While SWL is generally excepted as a first-line treatment option in ureteral stones because of its noninvasive nature, in situ lithotripsy, and especially PL, has higher success rates with minimal morbidity. Thus, PL seems to be a good alternative in patients in whom SWL was unsuccessful or not indicated and in patients who need early stone removal.
To compare the success rates, cost effectiveness, and efficiency of ureteroscopy (URS) and extracorporeal shock wave lithotripsy (ESWL) for proximal ureteral stones.
In a retrospective manner, 220 patients who underwent treatment for proximal ureteral stones were included in the study. The patient records, radiographs, and billing statements of all patients treated for upper ureteral stones between January 1997 and June 2001 at Scott and White Memorial Hospital were reviewed. The patients were placed into two treatment groups according to the method of their stone's initial treatment. The stones were categorized as less than 1 cm and 1 cm or greater.
A total of 111 patients were in the ESWL group, 73 of whom had stones less than 1 cm, and 109 patients in the URS group, 81 of whom had stones less than 1 cm. In the URS group, 91% were successfully treated with one treatment intervention, and 55% of the ESWL group were successfully treated with their initial intervention (P <0.0001). Of the patients with URS failure, all but one was treated successfully with a second URS. Of the patients with ESWL failure, 52% were treated successfully by subsequent URS. The remaining patients with ESWL failure were treated with repeat ESWL, with a 62% success rate. The efficiency quotient for stones less than 1 cm for URS and ESWL was 0.79 and 0.51, respectively. For stones 1 cm or greater, URS had an efficiency quotient of 0.72 and ESWL of 0.46. The URS group required fewer days to be stone free (8 versus 25.5 days, P <0.0001). No statistically significant difference was found in the overall complication rates (P = 0.43). URS had significantly lower charges for the initial procedure (7575 dollars versus 9507 dollars, P <0.0001). The total charges were also lower for URS (9378 dollars versus 15,583, dollars P <0.0001). Complications were similar in the two groups. The URS group had two ureteral strictures.
The results of this study indicate that URS is more efficient and cost-effective for stones up to and larger than 1 cm with similar complication rates compared with ESWL.
We quantified the burden of urolithiasis in the United States by identifying trends in the use of health care resources and estimating the economic impact of the disease.
The analytical methods used to generate these results have been described previously.
The rate of national inpatient hospitalizations for a diagnosis of urolithiasis decreased by 15% and hospital length of stay decreased from 2.6 to 2.2 days between 1994 and 2000. Rates of hospitalization were 2.5 to 3-fold higher for Medicare beneficiaries with little change between 1992 and 1998. Almost 2 million outpatient visits for a primary diagnosis of urolithiasis were recorded in 2000. Hospital outpatient visits increased by 40% between 1994 and 2000 and physician office visits increased by 43% between 1992 and 2000. In the Medicare population hospital outpatient and office visits increased by 29% and 41%, respectively, between 1992 and 1998. The distribution of surgical procedures remained relatively stable through the 1990s. Shock wave lithotripsy was the most commonly performed procedure, followed closely by ureteroscopy. Overall the total estimated annual expenditure for individuals with claims for a diagnosis of urolithiasis was almost 2 billion annually and it appears to be increasing with time despite a shift in inpatient to outpatient treatment and the emergence of minimally invasive treatment modalities, perhaps because the prevalence of stone disease is increasing.
Purpose:
The frequency doubled, double pulse Nd:YAG (FREDDY) laser (World of Medicine, Berlin, Germany) functions through the generation of a plasma bubble. Upon bubble collapse a mechanical shock wave is generated, causing stone fragmentation. This mechanism of action is in contrast to the holmium laser, which cause stone destruction by vaporization. Observed clinical stone retropulsion and fragmentation with the FREDDY and holmium lasers has prompted a series of in vitro experiments designed to compare laser induced retropulsion and fragmentation with those of a holmium laser and pneumatic lithotrite.
Materials and methods:
For retropulsion a hands-off underwater laboratory setup, including a horizontally oriented silicone tube 1.3 cm in diameter and a holder to keep the stone phantom in contact with the quartz laser fiber or pneumatic probe, was used. Previously weighed, cylindrical Bego stone phantoms (Bego USA, Smithfield, Rhode Island) were placed in the apparatus. Stone fragmentation was performed with the FREDDY or holmium laser, or the pneumatic lithotripter. The FREDDY and holmium lasers were tested at similar pulse energy and frequency settings. As a standard for comparison, a pneumatic lithotrite was tested with a semirigid probe and single pulse settings of 100, 200 and 300 kPa. Stone phantoms underwent 30 shocks per setting. Mean net retropulsion, defined as the final resting point of the stone, as determined by direct measurement, was recorded for each setting. For fragmentation plaster of Paris stone phantoms of known weights were used to compare the fragmentation ability of each laser. Stones phantoms were placed in a hands-off underwater setup, consisting of an inverted silicon syringe and holder immersed in tap water. The laser fiber (365 microm for the holmium and 280 microm for the FREDDY) was placed through the tip of the syringe in contact with the stone phantom. A total of 24 stones were divided into 4 groups of 6 per group. Two groups were fragmented with the FREDDY laser at 300 and 400 J total energy. The other 2 groups were fragmented using the holmium laser at 300 and 480 J total energy. Fragmentation efficiency was determined as percent weight loss.
Results:
For retropulsion at 160 mJ the FREDDY laser caused stone retropulsion to a mean distance of 7.6, 8.1 and 6.8 cm at settings of 5, 10 and 15 Hz, respectively. At 0.8 J the holmium laser retropulsed the stone to a mean distance of 3.3 and 4.9 cm at settings of 5 and 10 Hz, respectively. The pneumatic device caused stone retropulsion a mean distance of 8.5, 9.9 and 13.8 cm at pressure settings of 100, 200 and 300 kPa, respectively. The FREDDY laser generally caused less retropulsion than the pneumatic device, although this difference was only significant at the highest pneumatic lithoclast setting (p <0.05). At clinically relevant settings the FREDDY laser caused significantly more retropulsion than the holmium laser (p <0.05). For fragmentation at total energy settings of 300 and 400 J the FREDDY laser resulted in 44.9% and 86.8% weight loss, respectively (p <0.05). At settings of 300 and 480 J the holmium:YAG laser resulted in 3.3% and 7.1% weight loss, respectively (p <0.05).
Conclusions:
At lower frequency settings stone retropulsion was significantly greater with the FREDDY laser compared with the holmium laser. However, retropulsion was significantly less than that caused by the pneumatic lithotripter at all settings. Therefore, we recommend the use of an occlusive device, such as the Stone Cone (Boston Scientific, Natick, Massachusetts) proximal to the calculus during intracorporeal ureteral lithotripsy and in the ureteropelvic junction during percutaneous laser nephrostolithotomy. In vitro stone fragmentation was significantly greater with the FREDDY laser than with the holmium:YAG laser, suggesting that the FREDDY may offer a low cost alternative to the holmium:YAG laser lithotrite in select patients.
We sought to identify whether changes in technology and local practice have improved outcomes in the minimally invasive management of pediatric stone disease.
We reviewed retrospectively case notes and imaging from 1988 to 2003, noting treatment modality, stone-free rates, ancillary therapy and complications.
A total of 122 children (140 renal units) with a mean age of 7.7 years underwent 209 extracorporeal shock wave lithotripsy (SWL) sessions. Stone size ranged from 6 to 110 mm. Stone-free rates were 84% for cases involving stones smaller than 20 mm, and 54% for those involving stones 20 mm or greater. For complex calculi 40% of patients were stone-free and 45% required ancillary procedures, with an overall complication rate of 26%. A total of 37 children (43 renal units) with a mean age of 6.4 years underwent 46 percutaneous nephrolithotomies (PCNLs). Stone size ranged from 8 to 155 mm. The overall stone-free rate was 79%. Of these patients 34% required ancillary procedures, with a major complication rate of 6%. A total of 35 children (35 renal units) with a mean age of 5.9 years underwent 53 ureteroscopies. Holmium laser was the most effective treatment modality in this group, with a 100% stone-free rate and no complications.
For most renal stones smaller than 20 mm SWL was the most effective primary treatment modality. There was no statistical difference between the 2 lithotriptors for stone-free or ancillary procedure rate. The stone-free rate was dependent on stone size rather than type of lithotriptor. For renal stones 20 mm or greater and staghorn calculi we switched from SWL to PCNL as primary treatment, as stone-free rates were higher and the ancillary procedure and re-treatment rates were lower with PCNL. Electrohydraulic lithotripsy and pulse dye laser were initially used to treat ureteral stones. However, with the introduction of holmium laser technology we achieved higher stone-free rates and lower complication rates. Holmium laser lithotripsy is now used as a primary treatment modality for ureteral stones.
To study the efficiency and safety of holmium:YAG laser lithotripsy for ureteral stones.
A series of 188 patients with 208 ureteral stones were treated with semirigid ureteroscopy and holmium:YAG laser lithotripsy from January 2003 to December 2005. Of the stones, 116 were lower ureteral, 37 middle ureteral, and 55 upper ureteral.
The success rate was 92.7% at the time of ureteroscopy and 96.7% at 3 months. The failures were secondary to retropulsion of the stones (3.3%). There were no perforations and one stricture. Stenting was done in 90% of patients.
The Holmium:YAG laser is an ideal intracorporeal lithotripter for ureteral calculi, with a high success rate and low morbidity.
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was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.
The copyright holder for this preprint (which
this version posted June 3, 2024.
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