Optimising an escalating shockwave amplitude treatment strategy to protect the kidney from injury during shockwave lithotripsy

Is extracorporeal lithotripsy a first-line treatment for urinary stones today?

OBJECTIVE

To evaluate the efficacy and complications of extracorporeal lithotripsy (SWL) as a first-line treatment for renal and ureteral stones METHODS: Retrospective and observational study of all the patients treated with lithotripsy in a third level center between January 2014 and January 2021; characteristics of the patients, the stones, complications and results of SWL is recollected. Multivariate logistic regression of the factors associated with stone size reduction was performed. A statistical analysis of the factors associated with additional treatment after SWL and factors associated with complications is also executed.

RESULTS

1727 patients are included. Stone mean size was 9,5mm. 1540 (89.4%) patients presented reduction in stone size. In multivariate analysis, stone size (OR=1.13; p=0.00), ureteral location of the lithiasis (OR=1.15; p=0.052) and number of waves (p=0.002; OR=1.00) used in SWL are the factors associated with reduction of stone size. Additional treatment after lithotripsy was needed in 665 patients (38.5%). The factors associated with the need for retreatment were stone size (OR=1.131; p=0.000), number of waves (OR=1.000; p=0.000), energy (OR=1.005; p=0.000). 153 patients (8.8%) suffered complications after SWL. A statistically significant association was found between the size of the lithiasis (p=0.024, OR=1.054) and the previous urinary diversion (P=0.004, OR=0.571).

CONCLUSION

Lithotripsy remains an effective treatment as the first line of therapy for reno-ureteral lithiasis with a low percentage of complications.

International Alliance of Urolithiasis Guideline on Shockwave Lithotripsy

Different international associations have proposed their own guidelines on urolithiasis. However, the focus is primarily on an overview of the principles of urolithiasis management rather than step-by-step technical details for the procedure. The International Alliance of Urolithiasis (IAU) is releasing a series of guidelines on the management of urolithiasis. The current guideline on shockwave lithotripsy (SWL) is the third in the IAU guidelines series and provides a clinical framework for urologists and technicians performing SWL. A total of 49 recommendations are summarized and graded, covering the following aspects: indications and contraindications; preoperative patient evaluation; preoperative medication; prestenting; intraoperative analgesia or anesthesia; intraoperative position; stone localization and monitoring; machine and energy settings; intraoperative lithotripsy strategies; auxiliary therapy following SWL; evaluation of stone clearance; complications; and quality of life. The recommendations, tips, and tricks regarding SWL procedures summarized here provide important and necessary guidance for urologists along with technicians performing SWL. PATIENT SUMMARY: For kidney and urinary stones of less than 20 mm in size, shockwave lithotripsy (SWL) is an approach in which the stone is treated with shockwaves applied to the skin, without the need for surgery. Our recommendations on technical aspects of the procedure provide guidance for urologists and technicians performing SWL.

Which is better, fluoroscopic-guided or ultrasonic-guided shock wave lithotripsy for pediatric renal stones? Prospective randomized comparative study

OBJECTIVES

To compare the efficacy and clinical outcomes of two different stone localization modalities (fluoroscopic or ultrasonic) in SWL treatment of pediatric renal stones.

PATIENTS AND METHODS

This study was conducted in the period between January 2021 and June 2022 and included 100 children aged 2-16 years who presented with radio-opaque renal pelvic stones < 20 mm. The children were divided in two groups: group I, US-guided (50 patients), and group II, FS-guided SWL (50 patients). SWL was applied under general anesthesia. The follow-up of the patients included a visit every two weeks up to three months.

RESULTS

Even though group II's stone-free rate after one month of follow-up was higher than group I's (90% vs. 84%), no statistically significant difference was found between the groups (p = 0.749). While the success rate was higher in group II than in group I (92% vs. 86%), no statistically significant difference was observed between the two groups (p = 0.338). The complication rate was 28% (14 patients) and 12% (6 patients) in Groups I and II, respectively. However, no significant difference was found between the two groups (p = 0.132).

CONCLUSIONS

SWL is a non-invasive and safe method for treating pediatric renal stones. We recommend the use of the ultrasonic focusing modality in SWL of the pediatric age group, which has similar success rates, avoiding radiation and low complication rate instead of the fluoroscopic focusing modality, which uses ionizing radiation during SWL.

Functional and Morphological Changes Associated with Burst Wave Lithotripsy-Treated Pig Kidneys

Purpose: Burst wave lithotripsy (BWL) is a new technique for comminution of urinary stones. This technology is noninvasive, has a low positive pressure magnitude, and is thought to produce minor amounts of renal injury. However, little is known about the functional changes related to BWL treatment. In this study, we sought to determine if clinical BWL exposure produces a functional or morphological change in the kidney. Materials and Methods: Twelve female pigs were prepared for renal clearance assessment and served as either sham time controls (6) or were treated with BWL (6). In the treated group, 1 kidney in each pig was exposed to 18,000 pulses at 10 pulses/s with 20 cycles/pulse. Pressure levels related to each pulse were 12 and -7 MPa. Inulin (glomerular filtration rate, GFR) and para-aminohippuric acid (effective renal plasma flow, eRPF) clearance was measured before and 1 hour after treatment. Lesion size analysis was performed to assess the volume of hemorrhagic tissue injury created by each treatment (% FRV). Results: No visible gross hematuria was observed in any of the collected urine samples of the treated kidneys. BWL exposure also did not lead to a change in GFR or eRPF after treatment, nor did it cause a measurable amount of hemorrhage in the tissue. Conclusion: Using the clinical treatment parameters employed in this study, BWL did not cause an acute change in renal function or a hemorrhagic lesion.

Factors Affecting Tissue Cavitation during Burst Wave Lithotripsy

Burst wave lithotripsy (BWL) is a technology under clinical investigation for non-invasive fragmentation of urinary stones. Under certain ranges of ultrasound exposure parameters, this technology can cause cavitation in tissue leading to renal injury. This study sought to measure the focal pressure amplitude needed to cause cavitation in vivo and determine its consistency in native tissue, in an implanted stone model and under different exposure parameters. The kidneys of eight pigs were exposed to transcutaneous BWL ultrasound pulses. In each kidney, two locations were targeted: the renal sinus and the kidney parenchyma. Each was exposed for 5 min at a set pressure level and parameters, and cavitation was detected using an active cavitation imaging method based on power Doppler ultrasound. The threshold was determined by incrementing the pressure amplitude up or down after each 5-min interval until cavitation occurred/subsided. The pressure thresholds were remeasured postsurgery, targeting an implanted stone or collecting space (in sham). The presence of a stone or sham surgery did not significantly impact the threshold for tissue cavitation. Targeting parenchyma instead of kidney collecting space and lowering the ultrasound pulse repetition frequency both resulted in an increased pressure threshold for cavitation.

Automated Generation of Personalized Shock Wave Lithotripsy Protocols: Treatment Planning Using Deep Learning

Background

Though shock wave lithotripsy (SWL) has developed to be one of the most common treatment approaches for nephrolithiasis in recent decades, its treatment planning is often a trial-and-error process based on physicians’ subjective judgement. Physicians’ inexperience with this modality can lead to low-quality treatment and unnecessary risks to patients.

Objective

To improve the quality and consistency of shock wave lithotripsy treatment, we aimed to develop a deep learning model for generating the next treatment step by previous steps and preoperative patient characteristics and to produce personalized SWL treatment plans in a step-by-step protocol based on the deep learning model.

Methods

We developed a deep learning model to generate the optimal power level, shock rate, and number of shocks in the next step, given previous treatment steps encoded by long short-term memory neural networks and preoperative patient characteristics. We constructed a next-step data set (N=8583) from top practices of renal SWL treatments recorded in the International Stone Registry. Then, we trained the deep learning model and baseline models (linear regression, logistic regression, random forest, and support vector machine) with 90% of the samples and validated them with the remaining samples.

Results

The deep learning models for generating the next treatment steps outperformed the baseline models (accuracy = 98.8%, F1 = 98.0% for power levels; accuracy = 98.1%, F1 = 96.0% for shock rates; root mean squared error = 207, mean absolute error = 121 for numbers of shocks). The hypothesis testing showed no significant difference between steps generated by our model and the top practices (P=.480 for power levels; P=.782 for shock rates; P=.727 for numbers of shocks).

Conclusions

The high performance of our deep learning approach shows its treatment planning capability on par with top physicians. To the best of our knowledge, our framework is the first effort to implement automated planning of SWL treatment via deep learning. It is a promising technique in assisting treatment planning and physician training at low cost.

Renal Protection Phenomenon Observed in a Porcine Model After Electromagnetic Lithotripsy Using a Treatment Pause

Purpose: Pretreating the kidney with 100 low-energy shock waves (SWs) with a time pause before delivering a clinical dose of SWs (Dornier HM-3, 2000 SWs, 24 kV, and 120 SWs/min) has been shown to significantly reduce the size of the hemorrhagic lesion produced in that treated kidney, compared to a protocol without pretreatment. It has been assumed that a similar reduction in injury will occur with lithotripters other than the HM-3, but experiments to confirm this assumption are lacking. In this study, we sought to verify that the lesion protection phenomenon also occurs in a lithotripter using an electromagnetic shock source and dry-head coupling. Materials and Methods: Eleven female pigs were placed in a Dornier Compact S lithotripter where the left kidney of each animal was targeted for lithotripsy treatment. Some kidneys received 2500 SWs at power level (PL) = 5 (120 SWs/min) while some kidneys were pretreated with 100 SWs at PL = 1, with a 3-minute time pause, followed immediately by 2500 SWs at PL = 5 (120 SWs/min). Lesion size analysis was performed to assess the volume of hemorrhagic tissue injury created by each treatment regimen (% functional renal volume). Results: Lesion size fell by 85% (p = 0.01) in the 100 SW pretreatment group compared to the injury produced by a regimen without pretreatment. Conclusions: The results suggest that the treatment pause protection phenomenon occurs with a Dornier Compact S, a machine distinctly different from the Dornier HM-3. This result also suggests that this phenomenon may be observed generally in SW lithotripters.

Comparison of ultrasound-assisted and pure fluoroscopy-guided extracorporeal shockwave lithotripsy for renal stones

BACKGROUND

In this study, we aimed to compare the efficacy and clinical outcomes of shock wave lithotripsy (SWL) for patients with renal stones using pure fluoroscopy (FS) or ultrasound-assisted (USa) localization with two lithotripters.

METHODS

We retrospectively identified 425 patients with renal calculi who underwent SWL with either a LiteMed LM-9200 ELMA lithotripter (209 cases), which combined ultrasound and fluoroscopic stone targeting or a Medispec EM-1000 lithotripter machine (216 cases), which used fluoroscopy for stone localization and tracking. The patient demographic data, stone-free rates, stone disintegration rates, retreatment rates and complication rates were analyzed.

RESULTS

The USa group had a significantly higher overall stone-free rate (43.6 vs. 28.2%, p < 0.001) and stone disintegration rate (85.6 vs. 64.3%, p < 0.001), as well as a significantly lower retreatment rate (14.8 vs. 35.6%, p < 0.001) and complication rate (1.9 vs. 5.5%, p = 0.031) compared with the FS group. This superiority remained significant in the stone size < 1 cm stratified group. In the stone size > 1 cm group, the stone-free rate (32.4 vs. 17.8%, p = 0.028), disintegration rate (89.2 vs. 54.8%, p = 0.031) and retreatment rate (21.6 vs. 53.4%, p < 0.001) were still significantly better in the USa group, however there was no significant difference in the complication rate. The most common complication was post-SWL-related flank pain.

CONCLUSION

SWL is a safe and non-invasive way of treating renal stones. This study compared two electromagnetic shock wave machines with different stone tracking systems. LiteMed LM-9200 ELMA lithotripter, which combined ultrasound and fluoroscopic stone targeting outperformed Medispec EM-1000 lithotripter, which used fluoroscopy for stone localization and tracking, with better stone-free rates and disintegration rates, as well as lower retreatment rates and complications with possible reduced radiation exposure.

Laparotomy for duodenal obstruction, caused by a renal haematoma after extracorporeal shockwave lithotripsy

Extracorporeal shockwave lithotripsy is a widely used, acceptable and common first line treatment for non-conservatively managed renal and ureteric stone disease. Although considered a relatively safe non invasive treatment for renal and ureteric stones, can carry with it significant associated morbiditiy especially in high risk patients, such as those who are anticoagulated. Renal haematomas are not an uncommon finding after extracorporeal shockwave lithotripsy, however, fewer than 1% of patients presenting with a symptomatic renal haematoma require intervention in the form of urgent embolisation under interventional radiology, or emergency nephrectomy. Rare cases of splenic and hepatic haematomas have been reported and rarer still cases of gastro-intestinal perforation following extracorporeal shockwave lithotripsy. We report a case with a significant renal haematoma needing emergency embolisation of the renal artery, and subsequent development of duodenal obstruction from direct haematoma compression requiring a laparotomy and intended duodenal jejunal bypass.

Level of evidence: 5

Ultraslow full-power shock wave lithotripsy versus slow power-ramping shock wave lithotripsy in stones with high attenuation value: A randomized comparative study

OBJECTIVES

To compare the efficacy and safety of ultraslow full-power versus slow rate, power-ramping shock wave lithotripsy in the management of stones with a high attenuation value.

METHODS

This was a randomized comparative study enrolling patients with single high attenuation value (≥1000 Hounsfield unit) stones (≤3 cm) between September 2015 and May 2018. Patients with skin-to-stone distance >11 cm or body mass index >30 kg/m² were excluded. Electrohydraulic shock wave lithotripsy was carried out at rate of 30 shock waves/min for group A versus 60 shock waves/min for group B. In group A, power ramping was from 6 to 18 kV for 100 shock waves, then a safety pause for 2 min, followed by ramping 18-22 kV for 100 shock waves, then a safety pause for 2 min. This full power (22 kV) was maintained until the end of the session. In group B, power ramping was carried out with an increase of 4 kV each 500 shock waves, then maintained on 22 kV in the last 1000-1500 shock waves. Follow up was carried out up to 3 months after the last session. Perioperative data were compared, including the stone free rate (as a primary outcome) and complications (secondary outcome). Predicting factors for success were analyzed using logistic regression.

RESULTS

A total of 100 patients in group A and 96 patients in group B were included. The stone-free rate was significantly higher in group A (76% vs 38.5%; P < 0.001). Both groups were comparable in complication rates (20% vs 19.8%; P = 0.971). The stone-free rate remained significantly higher in group A in logistic regression analysis (odds ratio 24.011, 95% confidence interval 8.29-69.54; P < 0.001).

CONCLUSIONS

Ultraslow full-power shock wave lithotripsy for high attenuation value stones is associated with an improved stone-free rate without affecting safety. Further validation studies are required using other shock wave lithotripsy machines.

Inducing Different Brain Injury Levels Using Shock Wave Lithotripsy

OBJECTIVES

To assess the feasibility of inducing different severities of shock wave (SW)-induced traumatic brain injury (TBI) using lithotripsy.

METHODS

Wistar rats (n = 36) were divided into 2 groups: group 1 (n = 20) received 5 SW pulses, and group 2 (n = 16) received 15 SWs pulses. The SW pulses were delivered to the right side of the frontal cortex. Neurologic and behavioral assessments (Garcia test, beam walking, rotarod, and elevated plus maze) were performed at the baseline and at 3, 6, 24, 72, and 168 hours after injury. At day 7 after injury (168 hours), we performed cerebral angiography to assess the presence of cerebral vasospasm and vascular damage due to SW-induced TBI. At the conclusion of the study, the animals were euthanized to assess damage to brain tissue using an overall histologic severity score.

RESULTS

The Garcia score was significantly higher, and the anxiety index (based on the elevated plus maze) was significantly lower in group 1 compared to group 2 (P < .05). The anxiety index for group 1 returned to the baseline level in a fast nonlinear fashion, whereas the anxiety index for group 2 followed a distinct slow linear reduction. Cerebral angiograms revealed a more severe vasospasm for the animals in group 2 compared to group 1 (P = .027). We observed a statistically significant difference in the overall histologic severity scores between the groups. The median (interquartile range) overall histologic severity scores for groups 1 and 2 were 3.0 (2.75) and 6.5 (6.0), respectively (P = .023).

CONCLUSIONS

We have successfully established different SW-induced TBI severities in our SW-induced TBI model by delivering different numbers of SW pulses to brain tissue.

Indications and contraindications for shock wave lithotripsy and how to improve outcomes

For over 35 years shock wave lithotripsy has proven to be an effective, safe and truly minimally invasive option for the treatment of nephrolithiasis. Various technical factors as well as patient selection can impact the success of the procedure. We used published work focusing on outcomes of shock wave lithotripsy, risk of complications, and strategies for improving stone fragmentation to create this review. Multiple patient and technical factors have been found to impact success of treatment. Skin to stone distance, stone density and composition, size and location of the stone within the urinary system all influence stone free rates. A slower rate with a gradual increasing voltage, precise targeting, proper coupling will improve stone fragmentation and decrease risk of complications. The selection of appropriate patients through a shared decision making process and attention to the technical factors that improve stone free rates is key to providing an effective treatment and patient satisfaction.

Evaluation and physiopathology of minor transient shock wave lithotripsy - induced renal injury based on urinary biomarkers levels

Introduction

Extracorporeal shock wave lithotripsy (ESWL) is one of the most useful methods available for the treatment of urolithiasis. However, despite its significant benefits, adverse effects can occur. Oxidative stress mediated by ischemia-reperfusion might contribute to kidney injury after ESWL. Moreover, an acute kidney injury (AKI) may develop. AKI is typically diagnosed by measuring serum creatinine level, yet serum creatinine does not allow for early detection of sub-clinical AKI. The latest report has investigated multiple ways to determine ESWL - induced renal damage through the evaluation of various urine biomarkers of renal injury.

Materials and methods

The Medline and Web of Science databases were searched without a time limit in November 2017 using the terms 'ESWL' in conjunction with 'kidney failure', 'kidney damage', 'renal injury' and 'inflammation markers', 'biomarkers'. Boolean operators (NOT, AND, OR) were also used in succession to narrow and broaden the search. In this review, we described all the up-to-date reported urine markers of ESWL-induced renal damage.

Results

In recent years, several studies demonstrated evaluation of ESWL - induced renal injury based on urinary biomarkers levels and its utility in clinical practice. They have a beneficial role in the early detection of AKI, as well as in observation of a transition of this acute illness into chronic kidney disease.

Conclusions

Different markers have been evaluated in the urine before and after the ESWL treatment, but their number is still limited and results remain inconclusive. Further investigations are mandatory.

How can and should we optimize extracorporeal shockwave lithotripsy?

It is well recognized that the popularity of extracorporeal shock wave lithotripsy (SWL), despite its non-invasive character, has decreased during recent years. This is partly explained by the technological achievements in endoscopy and urologists’ enthusiasm for such procedures. Another explanation is that many urologists have been insufficiently successful with SWL. The latter effect might to some extent be a result of the performance of the lithotripter used, but in too many cases, it is evident that the principles of how shock wave lithotripsy should be carried out are poorly applied. The purpose of this article is to emphasize some important aspects on how SWL best should be used. Based on decades of experience, it stands to reason that success with SWL does not come automatically and attention has to be paid to all details of this technique.

Shockwave lithotripsy: techniques for improving outcomes

OBJECTIVES

Shock wave lithotripsy (SWL) remains the only effective truly non-invasive treatment for nephrolithiasis. While single-treatment success rates may not equal those of ureteroscopy and percutaneous nephrolithotomy, it has an important role to play in the management of stones. In this paper, we outline the latest evidence-based recommendations for maximizing SWL outcomes, while minimizing complications.

MATERIALS AND METHODS

A comprehensive review of the current literature was performed regarding maximizing SWL outcomes.

RESULTS

Several different considerations need to be made regarding patient selection with respect to body habitus, body mass index, anatomical location and underlying urologic abnormalities. Stone composition and stone density (Hounsfield Units) are important prognostic variables. Patient positioning is critical to allow for adequate stone localization with either fluoroscopy or ultrasound. Coupling should be optimized with a low viscosity gel applied to the therapy head first and patient movement should be limited. SWL energy should be increased slowly and shockwave rates of 60 or 90 Hz should be used. Medical expulsive therapy with alpha-blockers after SWL treatment has shown benefit, particularly with stones greater than 10 mm.

CONCLUSION

While single-treatment success rates may not equal those of ureteroscopy or percutaneous nephrolithotomy, with proper patient selection, optimization of SWL technique, and use of adjunctive treatment after SWL, success rates can be maximized while further reducing the already low rate of serious complications. SWL remains an excellent treatment option for calculi even in 2017.

Using 300 Pretreatment Shock Waves in a Voltage Ramping Protocol Can Significantly Reduce Tissue Injury During Extracorporeal Shock Wave Lithotripsy

PURPOSE

Pretreating a pig kidney with 500 low-energy shock waves (SWs) before delivering a clinical dose of SWs (2000 SWs, 24 kV, 120 SWs/min) has been shown to significantly reduce the size of the hemorrhagic lesion produced in that treated kidney, compared with a protocol without pretreatment. However, since the time available for patient care is limited, we wanted to determine if fewer pretreatment SWs could be used in this protocol. As such, we tested if pretreating with 300 SWs can initiate the same reduction in renal lesion size as has been observed with 500 SWs.

MATERIALS AND METHODS

Fifteen female farm pigs were placed in an unmodified Dornier HM-3 lithotripter, where the left kidney of each animal was targeted for lithotripsy treatment. The kidneys received 300 SWs at 12 kV (120 SWs/min) followed immediately by 2000 SWs at 24 kV (120 SWs/min) focused on the lower pole. These kidneys were compared with kidneys given a clinical dose of SWs with 500 SW pretreatment, and without pretreatment. Renal function was measured both before and after SW exposure, and lesion size analysis was performed to assess the volume of hemorrhagic tissue injury (% functional renal volume, FRV) created by the 300 SW pretreatment regimen.

RESULTS

Glomerular filtration rate fell significantly in the 300 SW pretreatment group by 1 hour after lithotripsy treatment. For most animals, low-energy pretreatment with 300 SWs significantly reduced the size of the hemorrhagic injury (to 0.8% ± 0.4%FRV) compared with the injury produced by a typical clinical dose of SWs.

CONCLUSIONS

The results suggest that 300 pretreatment SWs in a voltage ramping treatment regimen can initiate a protective response in the majority of treated kidneys and significantly reduce tissue injury in our model of lithotripsy injury.

Review on Lithotripsy and Cavitation in Urinary Stone Therapy

Cavitation is the sudden formation of vapor bubbles or voids in liquid media and occurs after rapid changes in pressure as a consequence of mechanical forces. It is mostly an undesirable phenomenon. Although the elimination of cavitation is a major topic in the study of fluid dynamics, its destructive nature could be exploited for therapeutic applications. Ultrasonic and hydrodynamic sources are two main origins for generating cavitation. The purpose of this review is to give the reader a general idea about the formation of cavitation phenomenon and existing biomedical applications of ultrasonic and hydrodynamic cavitation. Because of the high number of the studies on ultrasound cavitation in the literature, the main focus of this review is placed on the lithotripsy techniques, which have been widely used for the treatment of urinary stones. Accordingly, cavitation phenomenon and its basic concepts are presented in Section II. The significance of the ultrasound cavitation in the urinary stone treatment is discussed in Section III in detail and hydrodynamic cavitation as an important alternative for the ultrasound cavitation is included in Section IV. Finally, side effects of using both ultrasound and hydrodynamic cavitation in biomedical applications are presented in Section V.

Renal Vasoconstriction Occurs Early During Shockwave Lithotripsy in Humans

INTRODUCTION

In animal models, pretreatment with low-energy shock waves and a pause decreased renal injury from shockwave lithotripsy (SWL). This is associated with an increase in perioperative renal resistive index (RI). A perioperative rise is not seen without the protective protocol, which suggests that renal vasoconstriction during SWL plays a role in protecting the kidney from injury. The purpose of our study was to investigate whether there is an increase in renal RI during SWL in humans.

MATERIALS AND METHODS

Subjects were prospectively recruited from two hospitals. All subjects received an initial 250 shocks at low setting, followed by a 2-minute pause. Treatment power was then increased. Measurements of the renal RI were taken before start of procedure, at 250, after 750, after 1500 shocks, and at the end of the procedure. A linear mixed-effects model was used to compare RIs at the different time points.

RESULTS

Fifteen patients were enrolled. Average treatment time was 46 ± 8 minutes. Average RI at pretreatment, after 250, after 750, after 1500 shocks, and post-treatment was 0.67 ± 0.06, 0.69 ± 0.08, 0.71 ± 0.07, 0.73 ± 0.07, and 0.74 ± 0.06, respectively. In adjusted analyses, RI was significantly increased after 750 shocks compared with pretreatment (p = 0.05).

CONCLUSION

Renal RI increases early during SWL in humans with the protective protocol. Monitoring for a rise in RI during SWL is feasible and may provide real-time feedback as to when the kidney is protected.

Office-based stone management

As hospital resources are becoming strained, ambulatory surgical centers and day hospitals are being increasingly utilized. For the urologist, a working knowledge of local anesthetics and conscious sedation protocols are important, as many surgical kidney-stone procedures can be performed without general anesthetic. With any anesthesia, the key goal is to maximize patient comfort while minimizing respiratory depression and avoiding prolonged sedation. When using these medications, a working knowledge of emergency reversal, ventilation (bag mask/laryngeal mask airway/intubation), and cardiopulmonary resuscitation is recommended.

Evaluation of the LithoGold LG-380 lithotripter: in vitro acoustic characterization and assessment of renal injury in the pig model

PURPOSE

Conduct a laboratory evaluation of a novel low-pressure, broad focal zone electrohydraulic lithotripter (TRT LG-380).

METHODS

Mapping of the acoustic field of the LG-380, along with a Dornier HM3, a Storz Modulith SLX, and a XiXin CS2012 (XX-ES) lithotripter was performed using a fiberoptic hydrophone. A pig model was used to assess renal response to 3000 shockwaves (SW) administered by a multistep power ramping protocol at 60 SW/min, and when animals were treated at the maximum power setting at 120 SW/min. Injury to the kidney was assessed by quantitation of lesion size and routine measures of renal function.

RESULTS

SW amplitudes for the LG-380 ranged from (P(+)/P(-)) 7/-1.8 MPa at PL-1 to 21/-4 MPa at PL-11 while focal width measured ~20 mm, wider than the HM3 (8 mm), SLX (2.6 mm), or XX-ES (18 mm). For the LG-380, there was gradual narrowing of the focal width to ~10 mm after 5000 SWs, but this had negligible effect on breakage of model stones, because stones positioned at the periphery of the focal volume (10 mm off-axis) broke nearly as well as stones at the target point. Kidney injury measured less than 0.1% FRV (functional renal volume) for pigs treated using a gradual power ramping protocol at 60 SW/min and when SWs were delivered at maximum power at 120 SW/min.

CONCLUSIONS

The LG-380 exhibits the acoustic characteristics of a low-pressure, wide focal zone lithotripter and has the broadest focal width of any lithotripter yet reported. Although there was a gradual narrowing of focal width as the electrode aged, the efficiency of stone breakage was not affected. Because injury to the kidney was minimal when treatment followed either the recommended slow SW-rate multistep ramping protocol or when all SWs were delivered at fast SW-rate using maximum power, this appears to be a relatively safe lithotripter.

Shockwave lithotripsy-new concepts and optimizing treatment parameters

The treatment of kidney stone disease has changed dramatically over the past 30 years. This change is due in large part to the arrival of extracorporeal shock wave lithotripsy (ESWL). ESWL along with the advances in ureteroscopic and percutaneous techniques has led to the virtual extinction of open surgical treatments for kidney stone disease. Much research has gone into understanding how ESWL can be made more efficient and safe. This article discusses the parameters that can be used to optimize ESWL outcomes as well as the new concepts that are affecting the efficacy and efficiency of ESWL.