Burst wave lithotripsy and acoustic manipulation of stones

PURPOSE OF REVIEW

Burst wave lithotripsy and ultrasonic propulsion of kidney stones are novel, noninvasive emerging technologies to separately or synergistically fragment and reposition stones in an office setting. The purpose of this review is to discuss the latest refinements in technology, to update on testing of safety and efficacy, and to review future applications.

RECENT FINDINGS

Burst wave lithotripsy produced consistent, small passable fragments through transcutaneous applications in a porcine model, while producing minimal injury and clinical trials are now underway. A more efficient ultrasonic propulsion design that can also deliver burst wave lithotripsy effectively repositioned 95% of stones in 18 human participants (18 of 19 kidneys) and clinical trials continue. Acoustic tractor beam technology is an emerging technology with promising clinical applications through the manipulation of macroscopic objects.

SUMMARY

The goal of the reviewed work is an office-based system to image, fragment, and reposition urinary stones to facilitate their natural passage. The review highlights progress in establishing safety, effectiveness, and clinical benefit of these new technologies. The work is also anticipating challenges in clinical trials and developing the next generation of technology to improve on the technology as it is being commercialized today.

[Current status of extracorporeal shock wave lithotripsy in urinary lithiasis.]

Over the last decade, urinary lithiasis' prevalence has dramatically increased due to diet and lifestyle changes, growing 10.6% and 7.1% in men and women respectively. Extracorporeal shock wave lithotripsy has lost relevance in current practice due to endoscopic device development and unpredictability of results. Instrument miniaturization is leading to an increase of the percutaneous approach of increasingly smaller stones, while most flexible ureteroscopes durability and digitalization has allowed urologists to address larger stones. So that, decision algorithm is now impossible to define, but what is clear is that ESWL has declined worldwide. Can it disappear as a urinary lithiasis treatment modality? If we don't improve appropriate candidate selection and optimize disintegration efficiency, guidelines are going to replace the more "boring" ESWL by popular and more attractive endoscopes. Shock wave technology has evolved in the last two decades, however lithotripsy fundamental principle has not changed. ESWL has passed the test of time and centers dedicated to stone treatment should have a lithotripter in order to offer an appropriate balance in different options for different clinical situations. New developments will be focused on improvements in location (in-line navigation systems; Vision track system) and automatic ultrasound location on a robotic arm; monitoring and stone fixation, implementation of different focal sizes with new acoustic lenses, multitask working stations that allow endourological approach, coupling control (avoiding microbubbles) and low cost devices for different applications. On the other hand, optimizing outcomes by: slower pulse rates, ramping strategies and patient selection with soft stones, short stone-skin distance, low BMI and favorable collecting system anatomy, allow us to achieve better outcomes in shock wave treatments. SWL still represents a unique non invasive method of stone disease treatment with no anesthesia and low complication rates; and a high proportion of stones could still be treated with shock waves and remains among patient's first options. This update objective has been to review the evolution, identify shock wave new developments and clarify their impact on our daily practice in urinary stones treatment.

National Practice Pattern and Time Trends in Treatment of Upper Urinary Tract Calculi in Korea: a Nationwide Population-Based Study

Despite high prevalence of upper urinary tract calculi (UUTC), there are few studies regarding patterns of care in Asian populations. We investigated treatment patterns and time trends in patients with newly diagnosed UUTC in Korea using the National Health Insurance database that includes de-identified claims from a random 2% sample of the entire population (> 1 million people). A total of 14,282 patients who received active treatments, including shock wave lithotripsy (SWL), ureteroscopic surgery (URS), percutaneous nephrolithotomy (PNL), and uretero/pyelolithotomy (UPL), for newly diagnosed UUTC between 2003 and 2013 were included. The number of primary and all treated cases of UUTC significantly (43% and 103.3%, respectively) increased over the 10-year period. While patients undergoing SWL, URS, PNL, and UPL as primary treatment increased by 43.7%, 31.9%, 87.5%, and 0%, respectively, the relative proportion undergoing each treatment remained constant over the 10 years (SWL > 90%, URS 4.5% to 7.8%, PNL 0.4% to 1.0%, and UPL < 0.4%, respectively). Multinomial logistic regression analysis showed that age > 40 years (compared to age < 30 years) was significantly associated with URS, PNL, and UPL, rather than SWL, while patients living in urban or suburban/rural areas (compared to metropolitan) were significantly less likely to undergo URS and PNL. In summary, the majority of Korean patients underwent SWL as primary treatment for UUTC, and the predominant use of SWL remained steady over a 10-year period in Korea. Our results will be valuable in examining treatment patterns and time trends in Korean UUTC patients.

Renal calculi: trends in the utilization of shockwave lithotripsy and ureteroscopy

INTRODUCTION

To assess trends in the usage of extracorporeal shockwave lithotripsy (SWL) and ureteroscopy (URS) in the treatment of renal calculi.

MATERIALS AND METHODS

An analysis of the 5% Medicare Public Use Files (years 2001, 2004, 2007 and 2010) was performed to evaluate changes in the use of SWL and URS to treat renal calculi. Patients were identified using ICD-9 (cm) and CPT codes. Statistical analyses, including the Fisher, 2 tests, and multivariate logistic regression analysis were performed using SAS 9.3 (SAS Institute Inc., Cary, NC, USA) and SPSS v20 (IBM Corp., Armonk, NY, USA).

RESULTS

The absolute number of patients diagnosed with (+85.1%) and treated for (+31.5%) kidney calculi increased from 2001 to 2010. The ratio of diagnosed/treated patients declined from 15.2% in 2001 to 10.8% in 2010. Whites (OR = 1.27, p < 0.0001), patients in the South (OR = 1.16, p < 0.0001) and those ≤ 84 years of age were more likely to be treated. The utilization of SWL (84.7%) was greater than URS (15.3%), but the utilization of URS increased over time from 8.4% in 2001 to 20.6% of cases by 2010 (p < 0.0001). Treatment via URS was more likely in women (OR = 1.28, p < 0.0001), in patients living outside the South (OR = 1.29-1.45, p ≤ 0.006) and in later years of the study (OR = 2.87, p < 0.0001).

CONCLUSIONS

Treatment patterns for renal calculi changed from 2001 to 2010. The usage of URS increased at the cost of SWL. Multiple sociodemographic factors correlated with the likelihood of being treated surgically as well as the choice of the surgical approach.

Overview of therapeutic ultrasound applications and safety considerations

Applications of ultrasound in medicine for therapeutic purposes have been accepted and beneficial uses of ultrasonic biological effects for many years. Low-power ultrasound of about 1 MHz has been widely applied since the 1950s for physical therapy in conditions such as tendinitis and bursitis. In the 1980s, high-pressure-amplitude shock waves came into use for mechanically resolving kidney stones, and "lithotripsy" rapidly replaced surgery as the most frequent treatment choice. The use of ultrasonic energy for therapy continues to expand, and approved applications now include uterine fibroid ablation, cataract removal (phacoemulsification), surgical tissue cutting and hemostasis, transdermal drug delivery, and bone fracture healing, among others. Undesirable bioeffects can occur, including burns from thermal-based therapies and severe hemorrhage from mechanical-based therapies (eg, lithotripsy). In all of these therapeutic applications of ultrasound bioeffects, standardization, ultrasound dosimetry, benefits assurance, and side-effect risk minimization must be carefully considered to ensure an optimal benefit to risk ratio for the patient. Therapeutic ultrasound typically has well-defined benefits and risks and therefore presents a manageable safety problem to the clinician. However, safety information can be scattered, confusing, or subject to commercial conflicts of interest. Of paramount importance for managing this problem is the communication of practical safety information by authoritative groups, such as the American Institute of Ultrasound in Medicine, to the medical ultrasound community. In this overview, the Bioeffects Committee of the American Institute of Ultrasound in Medicine outlines the wide range of therapeutic ultrasound methods, which are in clinical use or under study, and provides general guidance for ensuring therapeutic ultrasound safety.

Optimizing Shock Wave Lithotripsy in the 21st Century

OBJECTIVE

Shock wave lithotripsy (SWL) has radically changed treatment of stone disease and appears to be the first option for the majority of patients. This review of current literature focused on suggestions for optimising technique, patient selection, results, and lithotriptor comparison for SWL.

METHODS

Literature search for SWL was performed for recently published papers in English language. Topics of interest were treatment protocols; patient evaluation; pre-SWL prediction of outcome; lithotriptor technology; efficacy; and methods to assess the effects, decrease complications, and compare lithotriptors. Earlier classic papers on SWL and guidelines for stone disease were also reviewed.

RESULTS

Recent literature contained important recommendations about SWL concerning (1) methods to predict stone fragmentation; (2) identification of factors contributing to treatment failure for lower pole and ureteric calculi; (3) guidelines from urological associations; (4) manoeuvres and changes in SWL delivery (slower rate, twin-pulse technique) to increase efficacy and decrease complications; (5) clarification of the role of medical treatment (antibiotics, alpha-blockers); (6) role of SWL in calyceal stones, CIRF, and abnormal kidneys; (7) obesity and SWL; and (8) methods to evaluate and compare lithotriptors.

CONCLUSIONS

SWL delivered in an outpatient setting as an anaesthesia-free treatment is still considered the first option for the majority of stones with a minimal number of complications. Better understanding of the physics of shockwave delivery is required, together with treatment optimisation by limiting renal damage and better selection of patients because this approach will offer maximum benefit to patients and physicians, as well as more cost-effective treatment.

Therapeutic applications of ultrasound

Therapeutic applications of ultrasound predate its use in imaging. A range of biological effects can be induced by ultrasound, depending on the exposure levels used. At low levels, beneficial, reversible cellular effects may be produced, whereas at high intensities instantaneous cell death is sought. Therapy ultrasound can therefore be broadly divided into "low power" and "high power" applications. The "low power" group includes physiotherapy, fracture repair, sonophoresis, sonoporation and gene therapy, whereas the most common use of "high power" ultrasound in medicine is probably now high intensity focused ultrasound. Therapeutic effect through the intensity spectrum is obtained by both thermal and non-thermal interaction mechanisms. At low intensities, acoustic streaming is likely to be significant, but at higher levels, heating and acoustic cavitation will predominate. While useful therapeutic effects are now being demonstrated clinically, the mechanisms by which they occur are often not well understood.

Extracorporeal shock wave lithotripsy 25 years later: complications and their prevention

OBJECTIVE

We review the pathophysiology and possible prevention measures of complications after extracorporeal shock wave lithotripsy (ESWL).

METHODS

A literature search was performed with the Medline database on ESWL between 1980 and 2004.

RESULTS

ESWL application has been intuitively connected to complications. These are related mostly to residual stone fragments, infections, and effects on tissues such as urinary, gastrointestinal, cardiovascular, genital, and reproductive systems. Recognition of ESWL limitations, use of alternative therapies, correction of pre-existing renal or systemic disease, treatment of urinary tract infection, use of prophylactic antibiotics, and improvement of ESWL efficacy are the most important measures of prevention. Decrease of shock wave number, rate and energy, use of two shock-wave tubes simultaneously, and delivery of two shock waves at carefully timed close intervals improve ESWL efficacy and safety.

CONCLUSION

ESWL is a safe method to treat stones when proper indications are followed. The need for well-designed prospective randomised trials on aetiology and prevention of its complications arises through the literature review.

Strategies for improved shock wave lithotripsy

Research in lithotripsy that started with the effort to characterize acute shock wave damage to the kidney has led to advances on several fronts, including discovery of strategies that have improved clinical treatment. It is appreciated now that shock wave trauma is primarily a vascular lesion, that injury is dose dependent, and that hemorrhage can be severe and can lead to a permanent loss of functional renal mass. Studies of the renal functional response to lithotripsy have shown that shock wave treatment triggers vasoconstriction in the kidney. This finding has been turned to advantage, and it is now known that when treatment is begun using low amplitude pulses, subsequent high amplitude shock waves are far less damaging. Thus, when shock waves are delivered judiciously, treatment can have a protective effect. The finding that cavitation is a key mechanism in vessel rupture has led to the development of novel experimental methods of shock wave delivery that can suppress bubble expansion and minimize tissue damage. Progress has also been made in understanding the physical mechanisms involved in stone comminution, and it is seen that the forces generated by cavitation, shear stress and circumferential squeezing act synergistically to fragment stones. Recent work suggests that a broad focal zone may be an advantage, allowing stones to be broken with lower amplitude pulses. Cavitation has been shown to play a critical role in reducing stone fragments to a size that can be voided. Cavitation is also the factor that limits the rate at which treatment can be performed, as stones break significantly better at slow rate than at fast ratean observation from basic research that is now appreciated in clinical practice. The current environment in lithotripsy research is encouraging. There is great interest in developing new technology, and in finding ways to improve how lithotripsy is performed.

Nephrolithiasis: "Scope," Shock or Scalpel?

PURPOSE

To evaluate treatment preferences for complex urinary calculi.

MATERIALS AND METHODS

A questionnaire was sent to 174 members of the Minnesota Urological Society. Three case scenarios were presented: a 1.5-cm lower-pole calculus with unfavorable anatomy, a 1.4-cm proximalureteral calculus, and a staghorn calculus. The treatment options offered were extracorporeal shockwave lithotripsy (SWL), ureteral stenting, ureteroscopy (URS), percutaneous nephrolithotomy (PCNL), and open surgery.

RESULTS

Our survey response rate was 49%. A PCNL for staghorn calculi was more likely to be offered by urologists in metropolitan (100%; P<0.001) and urban (100%; P=0.003) settings than rural settings (57%). Whereas only 22% of urban and metropolitan urologists would offer anatrophic nephrolithotomy, 43% of rural urologists would include this among their treatment options. A PCNL was more likely to be offered by urologists trained after 1980 (100%) than by urologists trained before 1980 (81%; P=0.004). For a large lower-pole calculus with unfavorable anatomy, urologists with >50% managed-care practices were more likely (91%) than urologists with <50% managed-care practices (65%) to select PCNL for such stones (P=0.034). Whereas 82% of metropolitan urologists would select PCNL, 43% of rural urologists would consider SWL as initial therapy. A URS was more likely to be offered by urologists trained after 1980 (16%) than by urologists trained before 1980 (0; P=0.044). For a large proximal-ureteral calculus, metropolitan urologists were most likely (64%) to use stents initially (urban 28%; P=0.014; rural 14%; P=0.017). Rural urologists were more likely to offer SWL (100%) than were metro urologists (55%; P=0.024).

CONCLUSIONS

Initial therapy for nephrolithiasis differs significantly according to geographic location, year of residency completion, and the percentage of managed-care patients in a urologist's practice. Future emphasis should be placed on increasing the availability of endoscopic techniques in rural settings.

Calculus fragmentation in laser lithotripsy

The intracorporeal treatment of urinary calculi with lasers is presented, which describes laser-calculus interactions associated with lithotripsy. Reliable fragmentation of calculi with diverse compositions and minimal collateral tissue damage are primarily contingent upon laser parameters (wavelength, pulse duration, and pulse energy) and physical properties of calculi (optical, mechanical, and chemical). The pulse duration governs the dominant mechanism in calculi fragmentation, which is either photothermal or photoacoustical/photomechanical. Lasers with long pulse durations (i.e. > tens of micros) induce a temperature rise in the laser-affected zone with minimal acoustic waves; material is removed by means of vaporization, melting, mechanical stress, and/or chemical decomposition. Short-pulsed laser ablation (i.e. < 10 micros), on the other hand, produces shock waves, and the resultant mechanical energy fragments calculi. Work continues throughout the world to evaluate the feasibility of advanced lasers in lithotripsy and to optimize laser parameters and light delivery systems pertinent to efficient fragmentation of calculi.

[Extracorporeal shock-wave lithotripsy. An established treatment]

Extracorporeal shock wave lithotripsy (ESWL) is the most required urinary stone therapy in our country and in the rest of the world. In a way it has replaced the alternative treatments (open surgery, percutaneous nephrolithectomy, ureteroscopy). Nevertheless these therapeutic approaches have still its own indications. Although there is no a definitive agreement, it should be desirable a world-wide consensus where each therapy will have a exactly defined land with all potential of each management improved. We review ESWL technical aspects, its literature-based most accepted indications, adverse bioeffects and last, future improvements are considered.

Current management of urolithiasis: progress or regress?

PURPOSE

To assess the impact of the development of less powerful second- and third-generation shockwave lithotripters on surgical stone therapy in light of recent advances in ureteroscopy and laser lithotripsy. As such, we sought to identify current trends in the treatment of stone disease, both at our university medical center and nationally, and to contrast them with the corresponding data from 1990.

PATIENTS AND METHODS

All urolithiasis procedures (ureteroscopy, SWL, open surgery, and percutaneous stone removal) performed in 1998 were compared with all urolithiasis procedures performed 8 years earlier (1990) at a single institution (Washington University, St. Louis). In addition, Medicare data for each year from 1988 through 2000 were collected from the Health Care Financing Administration to assess the national trends for open stone surgery, ureteroscopic stone removal, SWL, and percutaneous nephrolithotomy.

RESULTS

At Washington University, the number of percutaneous stone removals remained stable; however, the overall number of ureteroscopies increased by 53%, while the number of SWLs, decreased by 15%. The Medicare data likewise reflect a marked decrease in open stone surgery and a marked increase in ureteroscopic stone surgery with a slight increase in SWL. Utilization of percutaneous nephrolithotomy remained unchanged.

CONCLUSIONS

We believe this trend toward ureteroscopy is attributable to several factors: improved, smaller rigid and flexible ureteroscopes; the availability of more effective intracorporeal lithotripters (e.g., pneumatic and holmium laser), and the lack of development of lower cost, more effective SWL. This is an unfortunate trend, as we are moving away from the noninvasive treatment that was the hallmark of urolithiasis therapy at the beginning of the last decade toward more invasive endoscopic therapy. Increased research efforts in SWL technology are sorely needed.

A perspective on laser lithotripsy: the fragmentation processes

This paper describes in simple terms the physics of laser-calculus interactions and introduces a method with which physicians can understand or evaluate the application of any new laser technique for use in lithotripsy or other medical fields. Tissue optical properties and laser parameters govern the mechanism(s) of fragmentation of urinary or biliary calculi. Laser pulse energies for clinical lithotripsy range from Q0 = 20 mJ to 2 J for short-pulsed lasers to long-pulsed lasers, respectively. Lasers with short pulse durations (i.e., less than a few microseconds) fragment calculi by means of shockwaves following optical breakdown and plasma expansion of ionized water or calculus compositions or by cavitation collapse, thus manifesting a photoacoustical effect. Laser-tissue interactions involving dominant photomechanical or photoacoustical effects are usually stress confined. Long-pulsed lasers (i.e., >100 microsec), on the other hand, generate minimal acoustic waves, and calculi are fragmented by temperatures beyond the thresholds for vaporization of calculus constituents, melting, or chemical decomposition.

10-year experience with extracorporeal shockwave lithotripsy in the state of Colorado

PURPOSE

To evaluate trends in the utilization of extracorporeal shockwave lithotripsy (SWL) and the potential need for medical prophylaxis of urolithaisis in the state of Colorado.

MATERIALS AND METHODS

We examined patient and stone characteristics of individuals undergoing SWL for renal or upper-ureteral stones over a 10-year period (1987-1996) at the Kidney Stone Center of the Rocky Mountains. There were no significant changes in the in-state physician referral patterns nor SWL treatment criteria over this time interval. All patients were treated on the Dornier HM3 lithotripter. From September 1999 to December 1999, 198 consecutive patients undergoing SWL filled out a 10-point questionnaire regarding their interest in medical prophylaxis of urolithiasis.

RESULTS

The number of patients from Colorado rose 32.5%: from 15.7 per 100,000 population in 1987 to 20.8 per 100,000 in 1996. Patient demographics such as sex, race, age, and history of nephrolithiasis did not change. Furthermore, there were no significant changes in the treated stone size or stone location. The overall increase in treatment numbers was attributable equally to increases in the number of upper ureteral and renal stones. Of the 198 patients questioned, 114 (58%) were recurrent stone formers, but only 52 (45%) of these had been offered a metabolic evaluation.

CONCLUSIONS

Over the 10 years since the introduction of WSL in Colorado, there has been a gradual increase in its utilization. This higher utilization is probably multifactorial. Patients undergoing SWL have a strong desire to prevent future stone episodes and are very interested in medical prophylaxis of their stone disease.

Extracorporeal shock wave lithotripsy of gallstones revisited: current status and future promises

The improvement and refinement of extracorporeal shock wave lithotripsy (ESWL) has made this non-invasive treatment modality not only more effective, but also applicable to a larger population of gallstone patients. It can be performed safely on an outpatient basis. Advances in lithotripsy technology have made it possible to fragment stones into very small, sand-like particles (pulverization), which clear the gall-bladder faster than large fragments. Recent studies provide evidence that adjuvant bile acids may not be necessary in most cases in which pulverization is achieved. Good gall-bladder emptying appears both to promote the clearance of gallstones after ESWL and to decrease their recurrence. Although generally found to be more expensive than surgery if bile acids are used, ESWL should be cost-effective, as bile acids may not be necessary in all patients. Elderly patients with radiolucent, solitary and less than 30 mm gallstones can particularly benefit from lithotripsy.

Recent developments in SWL physics research

Two projects in our laboratory highlight some recent developments in shockwave lithotripsy (SWL) physics research. In the first project, we developed a prototype of a piezoelectric annular array (PEAA) shockwave generator that can be retrofitted on a Dornier HM-3 lithotripter for active control of cavitation during SWL. The PEAA generator, operating at 15 kV, produces a peak positive pressure of approximately 8 MPa with a -6-dB beam diameter of 5 mm. The shockwave generated by the PEAA was used to control and force the collapse of cavitation bubbles induced by a laboratory electrohydraulic shockwave lithotripter with a truncated HM-3 reflector. With optimal time delay between the lithotripter pulse and the PEAA-generated shockwave, the collapse of cavitation bubbles near the stone surface could be intensified, and the resultant stone fragmentation in vitro could be significantly improved. In the second project, high-speed shadowgraph imaging was used to visualize the dynamics of lithotripter-induced bubble oscillation in a vascular phantom. Compared with the free bubble oscillation in water, the expansion of cavitation bubble(s) produced in silicone tubes and a 200-microm cellulose hollow fiber by either a Nortech EHL or a Dornier XL-1 lithotripter was found to be significantly constrained. Rupture of the cellulose hollow fiber was observed consistently after about 20 shocks from the XL-1 lithotripter at an output voltage of 20 kV. These results confirm experimentally that SWL-induced cavitation in vivo can be significantly constrained by the surrounding tissue, and large intraluminal bubble expansions could cause rupture of capillaries and small blood vessels.

[Current aspects of extracorporeal lithotripsy (ECL)]

Basing on original experience (2150 cases) and literature data, the authors review in detail current status of EL: indications and contraindications, complications, pediatric applications, use in anomalous and single kidneys, in single, multiple and coral concrements. Prospects for the future are outlined.

[Changes in and acceptance of surgical and noninvasive therapy procedures in cholecystolithiasis]

BACKGROUND

The treatment of cholecystolithiasis has changed fundamentally in recent years due to the development of non-surgical techniques (extracorporeal shockwave lithotripsy [ESWL], oral litholysis) and the implementation of laparoscopic cholecystectomy.

PATIENTS AND RESULTS

Retrospective analysis of 2270 patients (1649 women, 621 men; age: 47.2 +/- 14 years) presenting with gallstone disorders in a university medical outpatients department between 1988 and 1992 in order to be instructed as to the most suitable therapy method bear witness to the rapid change in therapeutic procedure. Laparoscopic removal of the gallbladder has virtually supplanted conventional cholecystectomy, and within 5 years the proportionate role of ESWL has declined from 21 to 12%. Over the years, the proportion of patients requiring no therapeutic intervention remained constant (at about 20%). The therapeutic recommendations of the "experts" were implemented in almost 80% of cases. The majority of patients were satisfied with the chosen therapeutic approach (surgery: 93.0%, ESWL: 77.6%), although 44% of ESWL-patients and 36% of surgically managed patients reported complaints which persisted even after completion of therapy. Despite unsuccessful ESWL (residual fragments or recurrent stones) 58/95 (61%) of interviewed patients would again give preference to this non-invasive modality in the event of a renewed therapeutic decision.

CONCLUSION

Only a few years after its introduction, laparoscopic cholecystectomy has asserted itself as the predominant treatment option. But as far as acceptance and preference by the patient are concerned extracorporeal shockwave lithotripsy--as a non-invasive treatment modality--also enjoys high popularity and can be recommended as an alternative to surgery in suitable patients chosen according to the currently established stringent selection criteria.

[Current status of extracorporeal shockwave lithotripsy]

Extracorporeal shockwave lithotripsy has become an established standard procedure for the treatment of nephrolithiasis. Almost 100 lithotripters are installed in large and medium-sized urological departments in Germany. The number of treatments per year averages 660 ESWL sessions per hospital. Multifunctional use and non-urological ESWL therapy ensure maximum utilization of the lithotripter units. In additional hospitals mobile lithotripsy is provided. At present there is a trend toward ambulatory ESWL treatment.

[Extracorporeal lithotripsy and our future approach in lithiasis]

It can be claimed that ESWL is an optimal alternative for ablation of calculi by external shock waves. The new developments in ESWL focus more on the economic aspects of treatment rather than enhancing its efficacy or reducing the side effects. The routine indications of ESWL are well known and widely accepted. Similarly, its limitations are well defined: silent caliceal calculi, diverticular caliceal calculi, nephrolithiasis in horseshoe kidney, medullary sponge kidney and residual fragments after ESWL. Although endourology offers new, less invasive and less traumatic ways for stone ablation, such as lasertripsy, mini flexible ureteroscopes and ureteropyeloscopes, the indication for a more aggressive approach in the cases mentioned above is limited to the symptomatic cases. For calculi in the distal ureter, only the ureteroscope and intraureteral laser open new and interesting possibilities in the near future.

The dynamics of innovation in minimally invasive therapy

The emergence of minimally invasive therapy (MIT), which provides alternatives to major open-surgery procedures, is affecting all aspects of medical care delivery. In the present environment of resource and cost constraint in health services, an uncommon consensus among patients, physicians, providers, and payers has evolved regarding the rapid acceptance of this area of medical intervention, an acceptance that, in turn, is stimulating further innovation. This paper discusses the dynamics of medical innovation and analyzes these forces in the context of three minimally invasive therapies: percutaneous transluminal coronary angioplasty, extracorporeal shock wave lithotripsy, and laparoscopic cholecystectomy. The different experiences of the United States and Europe are used to illustrate how scientific, medical, economic, and regulatory factors affect both the rate and direction of technological change in minimally invasive therapy.

ESWL and the future of stone management

Based on optimal efficacy regarding disintegration and stone clearance, combined with minimal invasiveness, extracorporeal shockwave lithotripsy (ESWL) represents the first choice therapy for urolithiasis. Further developments in ESWL have related more to economic aspects than to improvement of disintegration efficacy or reduction of side effects. Routine indications for ESWL are well known and widely accepted. Its limitations are also well established: silent calyceal stones, calyceal diverticula stones, nephrolithiasis in horse-shoe kidneys, medullary sponge kidney, and residual fragments after ESWL. Although endourology provides new, less invasive and traumatic means of stone retrieval or disintegration, including laser lithotripsy, small ureteroscopes and actively deflectable uretero- and pyeloscopes, indications for an aggressive approach in such cases are limited to those who are symptomatic. In the case of distal ureteral calculi ureteroscopy in traureteral laser-induced shockwave lithotripsy open up new and interesting possibilities for the future.

Minimally invasive therapy: the French case study

The diffusion in France of the 10 selected technologies is quite different, depending on the technology. Some are 'ancient', widely diffused and stabilized techniques, such as arthroscopy for knee surgery and lithotripsy for bladder stones. Others are very new but quickly disseminating technologies, such as laparoscopic cholecystectomy, and others, especially those based on lasers, have only a restricted diffusion related in some cases to a lasting skepticism of most physicians. It is therefore not possible to draw a common sketch that would apply to 'minimally invasive surgery in France' as a whole. Nevertheless, it is possible to stress some common points which characterize the dissemination of innovation in the French health care system since the 1980s. These include the lack of methods available to health authorities to control medical innovation; the organizational and financial constraints on health care institutions, restricting their ability to adapt to changing circumstances; a limited judicial response in the face of potentially dangerous technologies; the high degree of freedom that medical practitioners have in adopting innovations; the weakness of French industry; and the important and sometimes destructive role the media play in diffusion of health care innovations.

[New trends in extracorporeal shockwave lithotripsy]

Extracorporeal shock wave lithotripsy has become an established and successful treatment modality for urinary and biliary calculi. However, shock wave technology and corresponding device designs are still at an innovative stage. Three trends are discussed in this paper. In shock wave technology the electromagnetic principle seems to win the race. The demands for successful and tissue-protective stone disintegration require shockwave sources with high dynamic range and optimised focal geometry. Electromagnetic shock wave generators meet all these requirements. For stone localisation an isocentric X-ray targeting system combined with integrated shock wave application is accepted as the "gold standard". In ultrasound localisation in-line targeting is superior to out-of-line targeting.

Minimally invasive therapy

A rapid change is taking place in the development of less invasive surgical and radiological techniques. The consequences of these changes may have considerable implications for clinical work patterns and institutional design in the next decade. Surgeons, radiologists and health economists must be prepared to recognise and react rapidly to these radical shifts in technology which are aimed at the reduction of patient morbidity and mortality.

Evolution of pre-treatment stenting and local anesthesia for extracorporeal shock wave lithotripsy at a single university center

Evolution of the extracorporeal shock wave lithotripsy technique involves not just second generation technology but operator innovations and experience. Retrospective analysis of the first 512 treatments at a university medical stone unit using the Dornier HM3 lithotriptor was compared to 3 intervals of 100 consecutive treatments during the next 2-year period (1985 to 1987). Patient referral and selection as well as treatment techniques and rates of endourological interventions were analyzed. Patient demographics, stone types and retreatment rates remained constant during 2,500 treatments. However, the use of local anesthesia and internal ureteral stents became increasingly common. Of the 1987 cohort 29% were treated with the patient under local anesthesia, and 23 of the 44 with a stent (52%) received internal ureteral stents. Other treatment trends identified during the study period included increasing number of large (greater than 2 cm.) and multiple stones treated; increasing use of internal and external ureteral catheters before treatment, fewer stents for small, mobile renal calculi and decreasing length of hospital stay (2.7 to 2.1 days) with increasing use of stents before lithotripsy. The increasing average number of shock waves per treatment (1,382 versus 1,580) during the study period can be attributed to the larger proportion of patients with high stone burdens and the impact of an increased number of operators with more varied criteria for endoscopy and treatment end point.