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.