Progress in Lithotriptor Technology

Factors influencing the efficacy of ultrasound-guided extracorporeal shockwave lithotripsy in the treatment of ureteral stones: a retrospective study

The aim of the study was to analyze the factors influencing the efficacy of ultrasound-guided extracorporeal shockwave lithotripsy (ESWL) in the treatment of ureteral stones. The clinical data of 8102 patients (6083 men and 2019 women) who presented with ureteral stones were retrospectively analyzed. All the patients were treated with ultrasound-guided ESWL. The stone-free rate (SFR) was calculated to evaluate the effect of ESWL. The characteristics of the patients and their stones, and the ESWL parameters applied were compared to identify the factors affecting the treatment outcomes. The SFR and that following one ESWL session were 94.6% (7663/8102) and 75.4% (6107/8102), respectively. Multivariate analysis showed that stone location (OR 0.656, p < 0.001), stone size (OR 1.103, p < 0.001), and degree of hydronephrosis (OR 1.952, p < 0.001) independently affected SFR; and age (OR 1.005, p = 0.022), stone location (OR 0.729, p < 0.001), stone size (OR 1.103, p < 0.001), degree of hydronephrosis (OR 1.387, p = 0.001), maximum energy level(OR 0.691, p < 0.001) independently affected SFR following one session. Ultrasound-guided ESWL is effective in all levels of ureteral stones. Large stone size and moderate hydronephrosis are correlated with treatment failure. Ultrasound-guided ESWL may be the first choice for distal ureteral stones.

Association between renal urolithiasis after extracorporeal shock wave lithotripsy therapy and new-onset hypertension: an updated meta-analysis

OBJECTIVE

The long-term effect of extracorporeal shock wave lithotripsy (SWL) is still controversial. A previous meta-analysis showed no association between new-onset hypertension and entire upper urinary urolithiasis after SWL. Recently, there have been some reports on this topic. Therefore, we aimed to examine the association between new-onset hypertension and nephrolithiasis after SWL therapy.

METHODS

Embase, the Cochrane Central Search Library, and PubMed were used to search for reports on new-onset hypertension and patients with nephrolithiasis after SWL. A meta-analysis of the association between new-onset hypertension and nephrolithiasis after SWL was carried out. The data of relevant research were synthesized and the relative risk was computed.

RESULTS

Seven eligible studies were included in our meta-analysis. There was a significant association between nephrolithiasis after SWL and new-onset hypertension. The overall relative risk with a 95% confidence interval was 1.21 (1.11-1.31) in a fixed-effects model.

CONCLUSION

Our meta-analysis suggests an association between new-onset hypertension and patients with nephrolithiasis after SWL, which is in contrast with the finding of a previous meta-analysis.

Evaluation of an experimental electrohydraulic discharge device for extracorporeal shock wave lithotripsy: Pressure field of sparker array

In this paper, an extracorporeal shock wave source composed of small ellipsoidal sparker units is described. The sparker units were arranged in an array designed to produce a coherent shock wave of sufficient strength to fracture kidney stones. The objective of this paper was to measure the acoustical output of this array of 18 individual sparker units and compare this array to commercial lithotripters. Representative waveforms acquired with a fiber-optic probe hydrophone at the geometric focus of the sparker array indicated that the sparker array produces a shock wave (P⁺ ∼40-47 MPa, P^- ∼2.5-5.0 MPa) similar to shock waves produced by a Dornier HM-3 or Dornier Compact S. The sparker array's pressure field map also appeared similar to the measurements from a HM-3 and Compact S. Compared to the HM-3, the electrohydraulic technology of the sparker array produced a more consistent SW pulse (shot-to-shot positive pressure value standard deviation of ±4.7 MPa vs ±3.3 MPa).

A prediction model for two-dimensional pressure distribution from underwater shock wave focusing by an ellipsoidal reflector

Underwater shock wave focusing by ellipsoidal reflector is an important method for medical treatment, detection, and acoustic warfare. However, its pressure field is difficult to predict due to complicated physics. In this study, the pressure by focusing is modeled based on theories of shock wave propagation, nonlinear reflection, and nonlinear focusing, and the calculation domain is determined by approximate equations of wave fronts and lines. The pressure field during the whole process is described by combining direct and focusing pressures in the time and space domains. On this basis, the focusing behavior is simulated, and obtained pressure profiles are compared with experimental results, and the influence of reflector length on focusing performance is also discussed. The results indicate that although there are some rough assumptions, this model can simulate the underwater focusing in some detail and does a good job of predicting the pressure distribution, especially for the positive peak pressure, with an error below 10%; as the reflector length increases, the dynamic focus tends to move linearly forward to the other geometric focus, and the pressure gain increases continuously but the growth rate decreases.

Extracorporeal shock wave lithotripsy for difficult common bile duct stones: a comparison between 2 different lithotripters in a large cohort of patients

BACKGROUND

Extracorporeal shock wave lithotripsy (ESWL) for difficult common bile duct (CBD) stones is a safe and effective treatment strategy allowing for bile duct clearance in approximately 90% of patients with a low incidence of mild adverse events.

OBJECTIVE

To compare the CBD clearance rates achieved after ESWL performed with 2 different lithotripters (Siemens Lithostar Plus and Storz Modulith SLX-F2) in a large cohort of patients with difficult CBD stones.

DESIGN

A retrospective analysis of a prospectively collected database.

SETTING

Tertiary care center.

PATIENTS

All of the consecutive patients who underwent ESWL because of difficult CBD stones between 1990 and 2012 were considered suitable for inclusion.

INTERVENTIONS

ESWL with Lithostar Plus or with Modulith SLX-F2.

MAIN OUTCOME MEASUREMENTS

CBD clearance.

RESULTS

Three hundred ninety-two patients with difficult CBD stones were treated; 199 patients were treated with the Lithostar Plus and 193 patients with the Modulith SLX-F2. CBD clearance was achieved in 349 patients (89.0%) with no significant difference between the patients treated with Lithostar Plus and those treated with Modulith SLX-F2 (90.5% vs 87.6%; P = .45). Patients treated with Modulith SLX-F2 underwent a significantly lower number of ESWL sessions (3 [range, 2 to 4] vs 3 [range, 2 to 4]; P = .0015), had a lower incidence of ESWL-related adverse events (5.2% vs 13.6%; P = .009), and never required opioid analgesia (P < .001).

LIMITATIONS

Retrospective design.

CONCLUSIONS

The Modulith SLX-F2 allows the same clearance rate as the Lithostar Plus but has a significantly lower incidence of adverse events and requires fewer ESWL sessions.

Optical coupling control: an important step toward better shockwave lithotripsy

BACKGROUND

In modern "dry" lithotripters, shockwaves are generated in a membrane-covered water cushion that is then coupled to the patient.To limit energy loss, a coupling agent, usually ultrasound gel, is used in this acoustic interface. During the coupling process, air pockets are inevitably trapped in the coupling area, which subsequently remains invisible to the operator. These air pockets dramatically decrease stone fragmentation efficiency up to 40%.

MATERIALS AND METHODS

To check for air bubbles in the coupling interface, a video camera was installed in the therapy head of our Dornier Gemini lithotripter: all air bubbles observed in the coupling zone could then be removed under visual control. We evaluated the effect of this optically controlled coupling (OCC) on treatment results (10/1/12-9/30/13) and compared these to the results obtained in a "blind" coupling mode (4/1/11-4/30/12).

RESULTS

Optically controlled removal of air bubbles from the coupling area reduced the required number of shockwaves with 25.4% for renal stones and 25.5% for ureteral stones. Energy level was reduced by 23.1% for renal stones and by 22.5% for ureteral stones. For renal stones, total applied energy was thus reduced by 42.9%. Effectiveness quotients were comparable.

CONCLUSIONS

Optical control with a video camera proved pivotal in the realization of bubble-free coupling. Bubble-free coupling significantly reduced the total energy needed to obtain comparable treatment results. Theoretically, this should also lead to a reduced incidence and severity of shockwave-induced adverse effects. We consider this an important step toward better and safer shockwave lithotripsy and would therefore advocate the standard incorporation of an OCC system in all new lithotripters.

An FDTD-based computer simulation platform for shock wave propagation in electrohydraulic lithotripsy

Extracorporeal Shock Wave Lithotripsy (ESWL) is based on disintegration of the kidney stone by delivering high-energy shock waves that are created outside the body and transmitted through the skin and body tissues. Nowadays high-energy shock waves are also used in orthopedic operations and investigated to be used in the treatment of myocardial infarction and cancer. Because of these new application areas novel lithotriptor designs are needed for different kinds of treatment strategies. In this study our aim was to develop a versatile computer simulation environment which would give the device designers working on various medical applications that use shock wave principle a substantial amount of flexibility while testing the effects of new parameters such as reflector size, material properties of the medium, water temperature, and different clinical scenarios. For this purpose, we created a finite-difference time-domain (FDTD)-based computational model in which most of the physical system parameters were defined as an input and/or as a variable in the simulations. We constructed a realistic computational model of a commercial electrohydraulic lithotriptor and optimized our simulation program using the results that were obtained by the manufacturer in an experimental setup. We, then, compared the simulation results with the results from an experimental setup in which oxygen level in water was varied. Finally, we studied the effects of changing the input parameters like ellipsoid size and material, temperature change in the wave propagation media, and shock wave source point misalignment. The simulation results were consistent with the experimental results and expected effects of variation in physical parameters of the system. The results of this study encourage further investigation and provide adequate evidence that the numerical modeling of a shock wave therapy system is feasible and can provide a practical means to test novel ideas in new device design procedures.

Stone comminution correlates with the average peak pressure incident on a stone during shock wave lithotripsy

To investigate the roles of lithotripter shock wave (LSW) parameters and cavitation in stone comminution, a series of in vitro fragmentation experiments have been conducted in water and 1,3-butanediol (a cavitation-suppressive fluid) at a variety of acoustic field positions of an electromagnetic shock wave lithotripter. Using field mapping data and integrated parameters averaged over a circular stone holder area (R(h)=7 mm), close logarithmic correlations between the average peak pressure (P(+(avg))) incident on the stone (D=10 mm BegoStone) and comminution efficiency after 500 and 1000 shocks have been identified. Moreover, the correlations have demonstrated distinctive thresholds in P(+(avg)) (5.3 MPa and 7.6 MPa for soft and hard stones, respectively), that are required to initiate stone fragmentation independent of surrounding fluid medium and LSW dose. These observations, should they be confirmed using other shock wave lithotripters, may provide an important field parameter (i.e., P(+(avg))) to guide appropriate application of SWL in clinics, and facilitate device comparison and design improvements in future lithotripters.

Impact of radiological technologists on the outcome of shock wave lithotripsy

OBJECTIVE

To evaluate the correlation of radiological technologists (RTs) and the outcome of shock wave lithotripsy (SWL) in terms of fluoroscopy time, fragmentation rate, and stone-free rate.

MATERIAL AND METHODS

A retrospective review of a prospectively collected database of 601 SWL treatments between June 2009 and March 2010 was performed. Patients with radiolucent stones were excluded. SWL was done by 6 RTs with different levels of experience. Follow up was available for 534 treatments. Multivariate analysis was performed.

RESULTS

RTs (A-F) performed 144, 109, 118, 58, 57, and 48 SWL sessions, respectively. There was no statistical difference among RTs in terms of mean stone size or stone location. Compared with other RTs, RT A had a significantly lower mean fluoroscopy time of 129 seconds (95% CI 120.8-137.3) (P <.001), higher stone-free rate (75.7%; P = .035), and stone fragmentation rate after a single SWL session (82.6%; P = .004). After correcting for stone size and location, fluoroscopy time (P <.001), fragmentation rate (P = .002), and stone-free rate (P = .04) maintained their significance. When comparing the top 3 RTs performing >100 SWL sessions, RTs B and C had significantly higher fluoroscopy time compared with RT A (OR [95% CI] 1.84 [1.38-2.45]; P <.001 and 2.67 [2.00-3.57]; P <.001), respectively. After correcting for stone size and location, RT B had significantly lower fragmentation rate when compared with RT A (OR [95% CI] 0.21 [0.05-0.86], P = .03]. However, there were no significant differences among the top 3 RTs in terms of stone-free rates.

CONCLUSION

RTs significantly differ in fluoroscopy usage in addition to stone fragmentation and stone-free rates.

Factors determining stone-free rate in shock wave lithotripsy using standard focus of Storz Modulith SLX-F2 lithotripter

OBJECTIVES

To calculate the efficiency quotient (EQ) of the latest mobile Storz Modulith SLX-F2 lithotripter and to identify the factors determining the stone-free rate.

METHODS

A retrospective review of a prospectively collected database of the first consecutive 533 patients undergoing shock wave lithotripsy (SWL) from June 2009 to February 2010 was performed. A total of 16 patients with radiolucent stones and 43 patients with incomplete follow-up were excluded. The patients were followed up with plain radiography to assess the stone-free status. Univariate and multivariate analyses were performed to identify the factors determining the stone-free rates.

RESULTS

Follow-up was complete for 474 patients, with a mean age of 54.2 ± 14.5 years. The success rate after a single SWL session was 82.7% (renal 82.2% and ureteral 83.3%; P = .81). The retreatment rate was 14.7% (renal 15.2% and ureteral 14.2%; P = .79). The stone-free rate was 77% (renal 74.1% and ureteral 80.9%; P = .10). Of the 474 patients, 43 had pre-SWL ureteral stents, and 13 required post-SWL ureteral stenting; 35 patients required post-SWL curative procedures. The EQ was 0.66, and the modified EQ was 0.62. On multivariate analysis, the stone-free patients had a smaller stone size (9.5 vs 10.3 mm, P = .02), younger age (53.1 vs 58.0 years, P = .002), right-sided stones (83.6% vs 71.0% P = .001), and the absence of a ureteral stent (78.7% vs 64.3%; P = .001).

CONCLUSIONS

The mobile Storz Modulith SLX-F2 lithotripter has an acceptable EQ of 0.66. In the present study, smaller stones (<10 mm), younger age, right-sided stones, and the absence of ureteral stents were associated with significantly greater stone-free rates.

Shock wave technology and application: an update

CONTEXT

The introduction of new lithotripters has increased problems associated with shock wave application. Recent studies concerning mechanisms of stone disintegration, shock wave focusing, coupling, and application have appeared that may address some of these problems.

OBJECTIVE

To present a consensus with respect to the physics and techniques used by urologists, physicists, and representatives of European lithotripter companies.

EVIDENCE ACQUISITION

We reviewed recent literature (PubMed, Embase, Medline) that focused on the physics of shock waves, theories of stone disintegration, and studies on optimising shock wave application. In addition, we used relevant information from a consensus meeting of the German Society of Shock Wave Lithotripsy.

EVIDENCE SYNTHESIS

Besides established mechanisms describing initial fragmentation (tear and shear forces, spallation, cavitation, quasi-static squeezing), the model of dynamic squeezing offers new insight in stone comminution. Manufacturers have modified sources to either enlarge the focal zone or offer different focal sizes. The efficacy of extracorporeal shock wave lithotripsy (ESWL) can be increased by lowering the pulse rate to 60-80 shock waves/min and by ramping the shock wave energy. With the water cushion, the quality of coupling has become a critical factor that depends on the amount, viscosity, and temperature of the gel. Fluoroscopy time can be reduced by automated localisation or the use of optical and acoustic tracking systems. There is a trend towards larger focal zones and lower shock wave pressures.

CONCLUSIONS

New theories for stone disintegration favour the use of shock wave sources with larger focal zones. Use of slower pulse rates, ramping strategies, and adequate coupling of the shock wave head can significantly increase the efficacy and safety of ESWL.

A simple method for fabricating artificial kidney stones of different physical properties

A simple method for preparing artificial kidney stones with varying physical properties is described. BegoStone was prepared with a powder-to-water ratio ranging from 15:3 to 15:6. The acoustic properties of the phantoms were characterized using an ultrasound transmission technique, from which the corresponding mechanical properties were calculated based on elastic wave theory. The measured parameters for BegoStone phantoms of different water contents are: longitudinal wave speed (3,148-4,159 m/s), transverse wave speed (1,813-2,319 m/s), density (1,563-1,995 kg/m(3)), longitudinal acoustic impedance (4.92-8.30 kg/m(2) s), transverse acoustic impedance (2.83-4.63 kg/m(2) s), Young's modulus (12.9-27.4 GPa), bulk modulus (8.6-20.2 GPa), and shear modulus (5.1-10.7 GPa), which cover the range of corresponding properties reported in natural kidney stones. In addition, diametral compression tests were carried out to determine tensile failure strength of the stone phantoms. BegoStone phantoms with varying water content at preparation have tensile failure strength from 6.9 to 16.3 MPa when tested dry and 3.2 to 7.1 MPa when tested in water-soaked condition. Overall, it is demonstrated that this new BegoStone preparation method can be used to fabricate artificial stones with physical properties matched with those of natural kidney stones of various chemical compositions.

Effect of lithotripter focal width on stone comminution in shock wave lithotripsy

Using a reflector insert, the original HM-3 lithotripter field at 20 kV was altered significantly with the peak positive pressure (p(+)) in the focal plane increased from 49 to 87 MPa while the -6 dB focal width decreased concomitantly from 11 to 4 mm. Using the original reflector, p(+) of 33 MPa with a -6 dB focal width of 18 mm were measured in a pre-focal plane 15-mm proximal to the lithotripter focus. However, the acoustic pulse energy delivered to a 28-mm diameter area around the lithotripter axis was comparable ( approximately 120 mJ). For all three exposure conditions, similar stone comminution ( approximately 70%) was produced in a mesh holder of 15 mm after 250 shocks. In contrast, stone comminution produced by the modified reflector either in a 15-mm finger cot (45%) or in a 30-mm membrane holder (14%) was significantly reduced from the corresponding values (56% and 26%) produced by the original reflector (no statistically significant differences were observed between the focal and pre-focal planes). These observations suggest that a low-pressure/broad focal width lithotripter field will produce better stone comminution than its counterpart with high-pressure/narrow focal width under clinically relevant in vitro comminution conditions.

Ultrasound monitoring of kidney stone extracorporeal shockwave lithotripsy with an external transducer: does fatty tissue cause image distortions that affect stone comminution?

INTRODUCTION

Ultrasound imaging, using either an inline or an external transducer, is a standard method for extracorporeal shockwave lithotripsy (SWL) monitoring. This study investigates whether image distortions caused by the low sound speed of fatty tissue could lead to incorrect stone positioning such that disintegration is affected.

MATERIALS AND METHODS

To define the accuracy needed for SWL monitoring, the dependency of fragmentation efficiency on the distance between stone center and SWL focus was examined by in vitro model stone tests. In a clinical study, 15 patients with kidney stones were treated with a Dornier Sigma FarSight. This lithotripter was equipped with both an inline and an external transducer. They were operated alternately to check for inconsistencies, which would indicate ultrasound image distortions. In addition, the ultrasound paths from the transducer to the SWL focus were analyzed for error estimation.

RESULTS AND DISCUSSION

In the model stone tests, the number of shock waves required for complete fragmentation doubled if the stone was about 7.5 to 10 mm off focus in lateral direction. In the clinical trial, the stone positions obtained from an inline and an external transducer coincided within a 5 mm range of tolerance, but that approach suffered from some practical difficulties, resulting in measurement imprecision. The sound path analysis showed that the lengths through fatty tissue were too short to result in significant image distortion. The body mass index (20-31 kg/m(2)) was representative, except for very obese patients. Additional confirmation of correct stone positioning could be achieved quite easily by looking for pixel movement in the B-mode image or employing Doppler hit/miss monitoring.

CONCLUSION

Within the study group, no image distortion caused by fatty tissue that could be clinically relevant for SWL was observed.

Lithotripsy

Shock wave lithotripsy (SWL) is the process of fragmentation of renal or ureteric stones by the use of repetitive shock waves generated outside the body and focused onto the stone. Following its introduction in 1980, SWL revolutionized the treatment of kidney stones by offering patients a non-invasive procedure. It is now seen as a mature technology and its use is perceived to be routine. It is noteworthy that, at the time of its introduction, there was a great effort to discover the mechanism(s) by which it works, and the type of sound field that is optimal. Although nearly three decades of subsequent research have increased the knowledge base significantly, the mechanisms are still controversial. Furthermore there is a growing body of evidence that SWL results in injury to the kidney which may have long-term side effects, such as new onset hypertension, although again there is much controversy within the field. Currently, use of lithotripsy is waning, particularly with the advent of minimally invasive ureteroscopic approaches. The goal here is to review the state of the art in SWL and to present the barriers and challenges that need to be addressed for SWL to deliver on its initial promise of a safe, effective, non-invasive treatment for kidney stones.

[Single center experience with Siemens Lithostar Modularis for treatment of 1500 solitiary urinary stones]

OBJECTIVES

the aim of the study was to evaluate the results of extracorporeal shock wave lithotripsy (ESWL) treatment with Siemens Lithostar Modularis in urinary stones.

PATIENTS AND METHODS

from May 2000 until September 2006, 1500 patients, 62% men and 38% women, ages 15 to 89 years (mean age 53), underwent ESWL as treatment of urinary stones at the Lithotripsy Unit of León. Data were analized retrospectively. More than half (56%) had left urinary stones. The most frequent ureteral localization (55%) was proximal (420 patients), and the most frecuent renal was renal pelvis (345 patients). The mean stone diameter was 1.3 cm. (1.01 ureteral and 1.7 renal). All patients received ESWL-session under i.v. analgesia with alfentanil and midazolam.

RESULTS

Mean number of sessions per lithiasis was 1.5 (ureteral stones 1.4 and renal stones 1.7). The retreatment rate was 33%, 28% for ureteral stones and 39% for renal stones with a cumulative success of 86% with two sessions. 22% of the patients required auxiliary manouvers, 24% of the patients with ureteral stones and 18% of the renal stones patients. Stone free rate was 91%, 97% in ureteral stones and 82% in renal stones.

CONCLUSIONS

treatment of urinary stones with Siemens Lithostar Modularis showed good results, with a stone free patient rate of more than 90%, although 33% of the patients need multiple ESWL treatment sessions and 20% of the patient required auxiliary procedures.

Outcomes using a fourth-generation lithotripter: a new benchmark for comparison?

OBJECTIVE

To evaluate the efficacy of a fourth-generation lithotripter, the Sonolith Vision (Technomed Medical Systems, Vaulx-en-Velin, France) for treating single previously untreated renal calculi, and to compare the results with the reference standard HM-3 (Dornier MedTech Europe GmbH, Wessling, Germany) in the same population originally studied by the USA Cooperative Study Group in 1986.

PATIENTS AND METHODS

The Sonolith Vision uses an innovative electroconductive shock-wave generator with an elliptical reflector specially designed to give the maximum concentration of energy on the stone. We reviewed the treatment sessions from our prospectively maintained database of the first 1000 consecutive patients with urinary stone disease who were treated with the Sonolith Vision between September 2004 and March 2006. Patients with previously untreated solitary renal calculi in anatomically normal kidneys were included. The outcome was assessed by plain films for radio-opaque stones, and renal ultrasonography for radiolucent stones, at 1 and 3 months after lithotripsy; the results were analysed according to stone size and location.

RESULTS

Data from 309 patients who had a complete follow-up and with 373 renal calculi that matched the above criteria were analysed. The initial fragmentation rate was 94%. The stone-free rate for stones of <10 mm was 77%, for 11-20 mm was 69% and for >20 mm was 50%. The overall stone-free rate 3 months after lithotripsy was 75%. Within a month of lithotripsy, 221 patients (59%) became stone-free. Additional procedures to render patients stone-free after lithotripsy were needed in only 22 cases (7%). The overall efficiency quotient was 62%. The stone-free rates for lower, upper, middle calyceal and renal pelvic calculi were 74%, 70%, 78.5% and 75%, respectively. There were no serious complications.

CONCLUSIONS

When similar populations of stone formers were assessed the Sonolith Vision achieved a high success rate, comparable with that using the HM-3 machine but with lower analgesia requirements and very low re-treatment rates. This method of comparison belies the commonly held view that newer lithotripters are less effective than the original spark-gap machines.

A new transportable shock-wave lithotripsy machine for managing urinary stones: a single-centre experience with a dual-focus lithotripter

OBJECTIVE

To assess the efficacy and safety of a transportable extracorporeal shock wave lithotripsy (ESWL) machine, the Modulith SLX-F2(TM) (Storz Medical Italia, Rome, Italy), in the management of solitary urinary calculi.

PATIENTS AND METHODS

The study included 233 patients (mean age 51 years; 172 male, 61 female) with symptomatic solitary renal (group A, 170, mean diameter 15.5 mm) or ureteric stones (group B, 63, mean diameter 9.5 mm) treated in a tertiary care institution. Exclusion criteria for the analysis were: pelvi-ureteric junction obstruction, multiple stones, stone diameter >2 cm, stones in a lower calyx with unfavourable anatomy, active infection, or impacted ureteric stones. Selected patients had ureteric stenting before treatment, and all patients were treated with no anaesthesia. Hospitalization, complications and subsequent auxiliary procedures were evaluated. Patients were assessed after a single ESWL session and after 3 months by a plain abdominal film and renal ultrasonography. Stone-free status was defined as no evidence of calculi, and clinical success as the presence of stone fragments of <4 mm. An efficiency quotient (EQ) was calculated for the ESWL treatment. Pain was assessed using a visual analogue scale.

RESULTS

The mean number of shocks used was 3779 and the mean (range) treatment time was 35 (5-55) min. The overall clinical success rate after one ESWL session was 83.7% and 82.5% for renal and ureteric stones, respectively, and the overall 3-month stone-free rate was 77% and 74.6%, respectively; the overall EQ was 0.64. When risk factors for persistent calculi were analysed simultaneously in a logistic regression model, only stones of >1 cm were statistically significant (P < 0.05). Most patients reported that pain during ESWL was mild to moderate and easily tolerated. Only minor complications occurred, with an overall complication rate of 3.8%.

CONCLUSIONS

This transportable lithotripter is a safe and effective device for managing solitary stones throughout the urinary tract. Its main advantage is represented by the dual-focus system. Moreover, it shares with other contemporary machines several important features such as outpatient setting, no need for anaesthesia, easy patient positioning, and the capability of ancillary procedures.

Efficacy and safety of a new-generation shockwave lithotripsy machine in the treatment of single renal or ureteral stones: Experience with 2670 patients

PURPOSE

To review the treatment efficacy and to assess the complications encountered in patients with single renal or ureteral calculi managed with a new-generation SWL machine, the Siemens Lithostar Modularis Uro-Plus.

PATIENTS AND METHODS

The stone location, size, minimum and maximum energy used, localization technique, number of shockwaves, fluoroscopy time, and number of sessions were reviewed for 2670 patients. The medical records were consulted to identify post-SWL secondary treatments in order to calculate the efficacy quotient (EQ).

RESULTS

The stone-free rate was 79%. Calculi in the renal pelvis and upper, middle, and lower ureter had success rates of 86%, 86%, 86%, and 85%, respectively (P < 0.05). Higher re-treatment rates were encountered for midureteral stones (P < 0.05). The major complications were renal hematoma, acute pyelonephritis, perirenal abscess, and acute pancreatitis. The overall EQ was 0.67. The EQ was higher for the renal pelvis (0.73) and upper ureter (0.71).

CONCLUSION

Our experience has shown that this new lithotripter is safe and provides a 68% to 86% chance of stone clearance.

A mechanistic analysis of stone fracture in lithotripsy

In vitro experiments and an elastic wave model were used to analyze how stress is induced in kidney stones by lithotripsy and to test the roles of individual mechanisms-spallation, squeezing, and cavitation. Cylindrical U30 cement stones were treated in an HM-3-style lithotripter. Baffles were used to block specific waves responsible for spallation or squeezing. Stones with and without surface cracks added to simulate cavitation damage were tested in glycerol (a cavitation suppressive medium). Each case was simulated using the elasticity equations for an isotropic medium. The calculated location of maximum stress compared well with the experimental observations of where stones fractured in two pieces. Higher calculated maximum tensile stress correlated with fewer shock waves required for fracture. The highest calculated tensile stresses resulted from shear waves initiated at the proximal corners and strengthened along the side surfaces of the stone by the liquid-borne lithotripter shock wave. Peak tensile stress was in the distal end of the stone where fracture occurred. Reflection of the longitudinal wave from the distal face of the stone--spallation-produced lower stresses. Surface cracks accelerated fragmentation when created near the location where the maximum stress was predicted.

ESWL Prediction of Outcome and Failure Prevention

Based on our own experiences and a review of the recent literature, this article evaluates recent developments in predicting outcomes and failures of shockwave lithotripsy when treating patients with urinary tract stones. After a detailed MEDLINE research, the authors identified several variables that influence and predict extracorporeal shockwave lithotripsy (ESWL) success. These variables may be categorized as stone variables, patient variables and operator variables. Only multivariate analysis on a large number of homogenous patients may offer an objective evaluation of the factors conditioning ESWL outcome.

A New Integrated Ultrasound System for Shockwave Lithotripsy

BACKGROUND AND PURPOSE

Inline ultrasound monitoring requires good image quality for accurate stone localization, as well as low shockwave shadowing and a robust transducer. In general, conventional transducers designed for another purpose, such as abdominal scanning, are employed. The distance between the transducer and the SWL focus can be varied by a mechanical drive. The drawback is reduced fragmentation at short distances and poor imaging at long distances. This paper introduces a new approach using a specially designed transducer without a mechanical drive.

MATERIALS AND METHODS

A transducer prototype with optimized beam focusing (B-K Medical, Herlev, Denmark) was integrated into a modified Compact Delta II therapy head (Dornier MedTech, Wessling, Germany). Image quality was tested at two clinical sites, where 40 kidney and 14 ureteral stones were treated. The shockwave was characterized by model stone tests and fiberoptic hydrophone measurements.

RESULTS

Both kidney and ureteral stone treatments could be monitored reliably. Despite the long distance to the SWL focus, the transducer could be operated with relatively high frequencies (3.5-6 MHz), so that high image resolution was obtained. Model stone tests yielded the same fragmentation as the standard Compact Delta II without a transducer.

CONCLUSIONS

This study shows that the concept of an integrated transducer distant from the shockwave focus is feasible. Transducer elevation, which is accompanied by shockwave shadowing and early transducer failure, is avoided by employing a dedicated transducer design.

Comparison of a New-Generation Electroconductive Spark Lithotripter and the Dornier Compact Delta for Ureteral Calculi in a Quaternary Referral Center

PURPOSE

The Technomed Sonolith Vision is the most recently developed electroconductive lithotripter. Using a case-control study, we compared the treatment outcomes of this machine with those of the Dornier Compact Delta for ureteral calculi.

PATIENTS AND METHODS

Patients (N = 107) with calculi from the ureteropelvic to the ureterovesical junction undergoing primary lithotripsy using the Technomed Sonolith Vision were identified between September 2004 and February 2005. All patients had 2-week and 3-month follow-up. These patients were compared with 524 patients from our database treated between October 2000 and August 2004 with a Dornier Compact Delta. The two groups were similar at baseline. Outcome variables measured were stone-free rate at 3 months, retreatment rate, and requirement for intravenous analgesia during the procedure.

RESULTS

There was a superior stone-free rate for the Technomed, reaching significance for calculi up to 7 mm. The Technomed had a significantly lower re-treatment rate for calculi <13 mm. There was no statistical difference in the requirement for intravenous analgesia. The Efficiency Quotient was superior for the Technomed (0.67 v 0.56).

CONCLUSIONS

This latest-generation electroconductive lithotripter in its first 6 months of use has shown stone-free and re-treatment rates superior to those of the Dornier Compact Delta and approaching that of the Dornier HM-3. Lithotripsy remains our first-line treatment for all radiopaque ureteral calculi.

Can Phyllanthus niruri Affect the Efficacy of Extracorporeal Shock Wave Lithotripsy for Renal Stones? A Randomized, Prospective, Long-Term Study

PURPOSE

Phyllanthus niruri is a plant used in Brazilian folk medicine for the treatment of urolithiasis. We assessed the efficacy of P. niruri after extracorporeal shock wave lithotripsy for renal stones.

MATERIALS AND METHODS

We prospectively evaluated 150 patients with renal stones that were as large as 25 mm and composed of calcium oxalate. All patients received 1 to 3 extracorporeal shock wave lithotripsy sessions by Dornier Lithotriptor S. After treatment 78 of 150 patients (52%) underwent therapy with Uriston, a P. niruri extract (2 gm daily) for at least 3 months (group 1). Otherwise 72 of 150 patients (48%) were used as a control group (group 2). No significant difference in stone size between the 2 groups was found. Stone clearance was assessed after 30, 60, 90 and 180 days by abdominal x-ray and ultrasound scan.

RESULTS

Stone-free rate (stone-free defined as the absence of any stone or residual fragments less than 3 mm) was 93.5% in group 1 and 83.3% in group 2 (p = 0.48) at the end point of the followup (180 days). For lower caliceal stones (56 patients) the stone-free rate was 93.7% in the treatment group and 70.8% in the control group (p = 0.01). Re-treatment need for group 1 was 39.7% and for group 2 it was 43.3% (p = 0.2). No side effects were recorded with extracorporeal shock wave lithotripsy or P. niruri therapy.

CONCLUSIONS

Regular self-administration of P. niruri after extracorporeal shock wave lithotripsy for renal stones results in an increased stone-free rate that appears statistically significant for lower caliceal location. Its efficacy and the absolute lack of side effects make this therapy suitable to improve overall outcomes after extracorporeal shock wave lithotripsy for lower pole stones.