Monitoring the coupling of the lithotripter therapy head with skin during routine shock wave lithotripsy with a surveillance camera

High-frequency shock wave lithotripsy: stone comminution and evaluation of renal parenchyma injury in a porcine ex-vivo model

BACKGROUND

The electrohydraulic high-frequency shock wave (Storz Medical, Taegerwilen, Switzerland) is a new way to create small fragments with frequencies up to 100 Hertz (Hz). This study evaluated the efficacy and safety of this method in a stone and porcine model.

MATERIALS AND METHODS

BEGO stones were put in a condom in a specifically designed fixture treated with different modulations to see stone comminution. Standardized ex vivo porcine model with perfused kidneys with 26 upper and lower poles of 15 kidneys was treated with the following modulations: voltage 16-24 kV, capacitor 12 nF and frequency up to 100 Hz. 2000-20,000 shock waves were applied to each pole. The kidneys were perfused with barium sulfate solution (BaSO4) and x-ray was performed to quantify the lesions using pixel volumetry.

RESULTS

There was no correlation between the number of shock waves and the powdering degree or the applied Energy and the grade of pulverization in the stone model. Regarding the perfused kidney model, the number of shock waves, applied voltage and frequency had no direct correlation with the occurrence of parenchymal lesions The detected lesions of the renal parenchyma were minimal, technical parameters had no significant impact and the lesions did not differ from the results of former experiments using 1-1.5 Hz in the same model.

CONCLUSIONS

High-frequency shock wave lithotripsy can produce small stone fragments to pass in a very short time. The injury to the renal parenchyma is comparable to the results of the conventional SWL using 1-1.5 Hz.

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.

A clinical observational study of effectiveness of a solid coupling medium in extracorporeal shock wave lithotripsy

This study aimed to investigate clinical effectiveness of stone disintegration by using isolation coupling pad (“icPad”) as coupling medium to reduce trapped air pockets during extracorporeal shock wave lithotripsy (ESWL). Patients underwent ESWL between Oct. 2017 and May 2018 were enrolled in this clinical observational study. An electromagnetic lithotripter (Dornier MedTech Europe GmbH Co., Germany) was used in this study. Patients were divided into icPad group P1, P2 and semi-gel group C by different coupling medium. The energy level and total number of shock wave (SW) for group P1 and C was set at level 2 and 3000 and group P2 at level 3 and 2500. The successful stone disintegration rate (SSDR) was determined to evaluate the treatment outcome. All patients were evaluated by KUB film and ultrasonography after 90 days. Complications during ESWL were recorded. A total of 300 patients satisfied the inclusion criteria. There were no significant differences in characteristics of patients and stone among three groups. The corresponding SSDRs for patients in group P1, P2 and C was 73.0%, 73.2% and 55.3%, respectively. The SSDR in group P1 was statistically higher than Group C. Comparing to semi-liquid gel, coupling medium using by icPad could achieve better treatment outcome of stone disintegration in ESWL.

Contemporary treatment trends for upper urinary tract stones in a total population analysis in Germany from 2006 to 2019: will shock wave lithotripsy become extinct?

PURPOSE

To describe the change in upper urinary tract stone management in Germany over a 14-year period.

METHODS

Using remote data processing we analyzed the nationwide German billing data from 2006 to 2019. To analyze the clinics' case numbers and regional trends, we used the reimbursement.INFO tool based on standardized quality reports of all German hospitals. To also cover shock wave lithotripsy (SWL) as an outpatient procedure, we analyzed the research database of the Institute for Applied Health Research with a representative anonymous sample of 4 million insured persons.

RESULTS

The number of inpatient interventional therapies for upper tract urolithiasis in Germany increased from 70,099 cases in 2006 to 94,815 cases in 2019 (trend p < 0.0001). In-hospital SWL declined from 41,687 cases in 2006 to 10,724 cases in 2019 (decline of 74%; trend p < 0.0001). The percentage of SWL as an outpatient procedure increased between 2013 and 2018 from 36 to 46% of all performed SWL, while total SWL case numbers declined. Contrarily, the number of ureteroscopies increased from 32,203 cases in 2006 to 78,125 cases in 2019 (increase of 143%; trend p < 0.0001). The number of percutaneous nephrolithotomy also increased from 1673 cases in 2006 to 8937 in 2019 (increase of 434%; trend p < 0.0001).

CONCLUSION

We observed an increase in interventional therapy for upper tract urolithiasis in Germany with a dramatic shift from SWL to endoscopic/percutaneous treatment. These changes may be attributed to enormous technological advances of the endoscopic armamentarium and to reimbursement issues.

In-vitro comparison of two electromagnetic shock-wave generators: low-pressure-wide focus versus high-pressure small focus - the impact on initial stone fragmentation and final stone comminution

CONTEXT

Recently developed concepts for higher efficacy ESWL with low-pressure wide focus systems resulting in finer fragmentation of the calculi.

OBJECTIVE

To compare two different electromagnetic shock wave sources (low-pressure wide focus (XL) versus high-pressure small focus (SL)) by sound-field measurements and in-vitro fragmentation.

EVIDENCE ACQUISITION

The CS-2012A XX-ES lithotripter (self-focusing electromagnetic shock-wave generator with concave spherical curved electrical coil; Xinin Lithotripter = XL) was compared to the Siemens Lithoskop (= SL) (electromagnetic generator with a flat electric coil with an acoustical lens). Different sound-field measurements were performed using a fiber-optic hydrophone. Measurements at three different power settings (XL: 8.0kV, 9.3kV and 10.3kV; SL: Level 1, 5 and 8). 10 ATS-stones and 15 BegoStones (9.3 kV, Level 3) with a frequency of 90/minute (SL) and 20/minute (XL). Number of impulses to the first crack and for complete stone comminution (residual fragments <2mm) were documented.

RESULTS

The median number of shock waves for the first crack in ATS-stones with the XL was 12 (10-14), with the SL 7 (6-9). Complete disintegration was accomplished after 815 (782-824) shock waves with XL, 702 (688-712) with SL. The difference was not statistically significant. The median number of shock waves to produce the first crack in BegoStones was 524 (504-542) with XL and only 151 (137-161) with SL. Numbers of shock waves for complete disintegration did not differ significantly (XL:2518 vs SL:2287). Using a wide focus with low pressure shows more homogeneous disintegration.

CONCLUSION

Two stone models showed significant differences regarding form and time of the initial fragmentation. Impulses for stone comminution did not differ significantly. The advantages of a low-pressure wide focus-system include minimal trauma and a homogeneous fragment size but is more time consuming. High-pressure small focus systems are clinically effective.

Extracorporeal shock-wave lithotripsy: is it still valid in the era of robotic endourology? Can it be more efficient?

PURPOSE OF REVIEW

The aim of the article is to evaluate the actual role of extracorporeal shock-wave lithotripsy (ESWL) in the management of urolithiasis based on the new developments of flexible ureterorenoscopy (FURS) and percutaneous nephrolithotomy (PCNL).

RECENT FINDINGS

In Western Europe, there is a significant change of techniques used for treatment of renal stones with an increase of FURS and a decrease of ESWL. The reasons for this include the change of indications, technical improvement of the endourologic armamentarium, including robotic assistance. Mostly relevant is the introduction of digital reusable and single-use flexible ureterorenoscopes, whereas micro-PCNL has been abandoned. Some companies have stopped production of lithotripters and novel ideas to improve the efficacy of shock waves have not been implemented in the actual systems. Promising shock-wave technologies include the use of burst-shock-wave lithotripsy (SWL) or high-frequent ESWL. The main advantage would be the very fast pulverization of the stone as shown in in-vitro models.

SUMMARY

The role of ESWL in the management of urolithiasis is decreasing, whereas FURS is constantly progressing. Quality and safety of intracorporeal shock-wave lithotripsy using holmium:YAG-laser under endoscopic control clearly outweighs the advantages of noninvasive ESWL. To regain ground, new technologies like burst-SWL or high-frequent ESWL have to be implemented in new systems.

Experimental observations and numerical modeling of lipid-shell microbubbles with calcium-adhering moieties for minimally-invasive treatment of urinary stones

A novel treatment modality incorporating calcium-adhering microbubbles has recently entered human clinical trials as a new minimally-invasive approach to treat urinary stones. In this treatment method, lipid-shell gas-core microbubbles can be introduced into the urinary tract through a catheter. Lipid moities with calcium-adherance properties incorporated into the lipid shell facilitate binding to stones. The microbubbles can be excited by an extracorporeal source of quasi-collimated ultrasound. Alternatively, the microbubbles can be excited by an intraluminal source, such as a fiber-optic laser. With either excitation technique, calcium-adhering microbubbles can significantly increase rates of erosion, pitting, and fragmentation of stones. We report here on new experiments using high-speed photography to characterize microbubble expansion and collapse. The bubble geometry observed in the experiments was used as one of the initial shapes for the numerical modeling. The modeling showed that the bubble dynamics strongly depends on bubble shape and stand-off distance. For the experimentally observed shape of microbubbles, the numerical modeling showed that the collapse of the microbubbles was associated with pressure increases of some two-to-three orders of magnitude compared to the excitation source pressures. This in-vitro study provides key insights into the use of microbubbles with calcium-adhering moieties in treatment of urinary stones.

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.

[Extracorporeal shock wave lithotripsy]

Interventional treatment of stones essentially consists of three treatment modalities. Extracorporeal shockwave lithotripsy (ESWL), in addition to uterorenoscopy (URS) and percutaneous nephrolitholapaxy (PCNL) is an essential treatment pillar and is the only noninvasive therapy option for the treatment of urinary stones. After a long period of ESWL being the leading choice in stone treatment, the number of SWL interventions diminished in recent years in favor of the other two treatment modalities (URS and PCNL). This article describes the indications, surgical technique and management of complications of SWL.

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.

A new optical coupling control technique and application in SWL

The objective of this study was to compare the results of shock wave lithotripsy (SWL) between patients treated with optical coupling control (OCC) and those treated with "blind" coupling during SWL to treat renal stones. Enrolled in the study were patients with urinary stones who underwent SWL between January 2014 and February 2015. The lithotripter used in the study was an electromagnetic Dornier Compact Delta II UIMS. The closed envelope method was used to randomize the enroled patients to OCC (Group A) or "Blind" coupling group (Group B). The stone-free rates (SFRs) were determined using KUB film with or without ultrasonography after 3 months. Treatment failure was defined as radiologically confirmed persistence of the stone with no fragmentation after second SWL sessions. Complications during the intraoperative or post-operative periods were recorded. A total of 336 patients satisfied the inclusion criteria for the study, of which 169 patients were treated in the Group A and 167 in the Group B. There was no significant difference in patient and stone characteristics between the two groups (Table 1). The locations of treated stones are shown in Table 2. The treatment results were stratified by stone location in Table 3, significant differences existed in all treatment results between the two groups (P < 0.05). The overall stone-free rates after 3 months were 78.2 % for kidney stones and 81.7 % for ureteral stones in patients from Group A. The corresponding SFRs for patients in Group B were 62.8 and 67.9 % for stones in the kidneys and ureters, respectively. There were statistical differences in these results between the two groups (P < 0.05). The lithotripter with OCC had excellent shock wave transmission properties with the least possible loss of energy; it can lead to the optimization of SWL treatment outcome and reduce the incidence of SW-induced adverse effects. We are confident that the OCC used in this study should be a standard feature in future lithotripters. Table 1 Patients' and stones' characteristics Group A Group B P value Number of patients 169 167 Patients' gender (M/F) 97/72 109/58 0.138 Stone location (left/right) 86/83 89/78 0.659 Patients' age (years) 36.3 ± 7.1 34.2 ± 6.8 0.521 Size of stones  Kidney (cm) 1.4 ± 0.6 1.3 ± 0.7 0.452  Ureter (cm) 1.1 ± 0.5 1.1 ± 0.4 0.354  Average size (cm) 1.2 ± 0.8 1.2 ± 0.7 0.372 Table 2 The distribution of location of stones treated Group A % Group B % Upper calyx 21 12.4 25 15.0 Middle calyx 28 16.6 23 13.8 Lower calyx 7 4.1 5 3.0 Renal pelvis 31 18.3 33 19.8 Upper ureter 28 16.6 31 18.6 Middle ureter 6 3.6 4 2.4 Lower ureter 48 28.4 46 27.5 Overall 169 100.0 167 100.0 Table 3 The treatment results were stratified by stone location Group A Group B %Stone-free %Re-treatment %Ancillary procedure %Stone-free %Re-treatment %Ancillary procedure Kidney  Upper calyx 76.2 33.3 14.3 60.0 48.0 12.0  Middle calyx 75.0 35.7 7.1 56.5 56.5 13.0  Lower calyx 71.4 42.9 28.6 60.0 60.0 40.0  Renal pelvis 83.9 29.0 9.7 69.7 45.5 12.1  Overall 78.2 33.3 11.5 62.8 50. 0 14.0 Ureter  Upper ureter 82.1 28.6 10.7 74.2 32.3 16.1  Middle ureter 66.7 66.7 33.3 50. 75.0 50.0  Lower ureter 83.3 25.0 10.4 65.0 41.3 13.0  Overall 81.7 29.3 12.2 67.9 39.5 16.0.

Arguments for choosing extracorporeal shockwave lithotripsy for removal of urinary tract stones

At a time when there is an almost unlimited enthusiasm and preference among urologists for endoscopic stone removal, we have found it essential to meet some of the frequently presented arguments on why extracorporeal shockwave lithotripsy (SWL) should not be used. We have based our considerations in this brief article on our 30-35 years' experience with the non-invasive or least invasive technique that SWL represents. Stone disintegration, requirement of repeated treatment sessions, the concern of residual fragments, complications and economic aspects are some points that are discussed.

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.

Extracorporeal shock wave lithotripsy: An opinion on its future

The development of miniaturized nephroscopes which allow one-stage stone clearance with minimal morbidity has brought the role of shock wave lithotripsy (SWL) in stone management into question. Design innovations in SWL machines over the last decade have attempted to address this problem. We reviewed the recent literature on SWL using a MEDLINE/PUBMED research. For commenting on the future of SWL, we took the subjective opinion of two senior urologists, one mid-level expert, and an upcoming junior fellow. There have been a number of recent changes in lithotripter design and techniques. This includes the use of multiple focus machines and improved coupling designs. Additional changes involve better localization real-time monitoring. The main goal of stone treatment today seems to be to get rid of the stone in one session rather than being treated multiple times non-invasively. Stone treatment in the future will be individualized by genetic screening of stone formers, using improved SWL devices for small stones only. However, there is still no consensus about the design of the ideal lithotripter. Innovative concepts such as emergency SWL for ureteric stones may be implemented in clinical routine.

Extracorporeal shock wave lithotripsy today

Even 32 years after its first introduction shockwave lithotripsy (SWL) remains a matter of discussion and controversy. Since the first SWL in 1980, millions of treatments have been performed worldwide. To this day SWL remains the least invasive of all stone treatments and is considered the treatment modality of first choice for the majority of urinary stones. Despite the massive scale on which SWL is performed in a wide range of indications, complication rate has always remained very low and usually limited to minor side effects and complications. The introduction of affordable multifunctional lithotripters has made SWL available to more and more departments of urology worldwide. Still many centers are disappointed with the treatment results and concerned about the adverse tissue effects. In this SWL proves to be the victim of its uninvasiveness and its apparent ease of practice. Urologists need proper skill and experience; however, to adequately administer shockwaves in order to improve outcome. This aspect is too often minimized and neglected. Apart from this the power of shockwaves often is underestimated by operators of shockwave machines. Basic knowledge of the physics of shockwaves could further reduce the already minimal adverse tissue effects. Good training and coaching in the administration of shockwaves would no doubt lead to a renaissance of SWL with better treatment results and minimal adverse tissue effects.

Size and location of defects at the coupling interface affect lithotripter performance

Study Type--Therapy (case series) Level of Evidence 4. What's known on the subject? and What does the study add? In shock wave lithotripsy air pockets tend to get caught between the therapy head of the lithotripter and the skin of the patient. Defects at the coupling interface hinder the transmission of shock wave energy into the body, reducing the effectiveness of treatment. This in vitro study shows that ineffective coupling not only blocks the transmission of acoustic pulses but also alters the properties of shock waves involved in the mechanisms of stone breakage, with the effect dependent on the size and location of defects at the coupling interface.

OBJECTIVE

• To determine how the size and location of coupling defects caught between the therapy head of a lithotripter and the skin of a surrogate patient (i.e. the acoustic window of a test chamber) affect the features of shock waves responsible for stone breakage.

MATERIALS AND METHODS

• Model defects were placed in the coupling gel between the therapy head of a Dornier Compact-S electromagnetic lithotripter (Dornier MedTech, Kennesaw, GA, USA) and the Mylar (biaxially oriented polyethylene terephthalate) (DuPont Teijin Films, Chester, VA, USA) window of a water-filled coupling test system. • A fibre-optic probe hydrophone was used to measure acoustic pressures and map the lateral dimensions of the focal zone of the lithotripter. • The effect of coupling conditions on stone breakage was assessed using gypsum model stones.

RESULTS

• Stone breakage decreased in proportion to the area of the coupling defect; a centrally located defect blocking only 18% of the transmission area reduced stone breakage by an average of almost 30%. • The effect on stone breakage was greater for defects located on-axis and decreased as the defect was moved laterally; an 18% defect located near the periphery of the coupling window (2.0 cm off-axis) reduced stone breakage by only ~15% compared to when coupling was completely unobstructed. • Defects centred within the coupling window acted to narrow the focal width of the lithotripter; an 8.2% defect reduced the focal width ~30% compared to no obstruction (4.4 mm vs 6.5 mm). • Coupling defects located slightly off centre disrupted the symmetry of the acoustic field; an 18% defect positioned 1.0 cm off-axis shifted the focus of maximum positive pressure ~1.0 mm laterally. • Defects on and off-axis imposed a significant reduction in the energy density of shock waves across the focal zone.

CONCLUSIONS

• In addition to blocking the transmission of shock-wave energy, coupling defects also disrupt the properties of shock waves that play a role in stone breakage, including the focal width of the lithotripter and the symmetry of the acoustic field • The effect is dependent on the size and location of defects, with defects near the centre of the coupling window having the greatest effect. • These data emphasize the importance of eliminating air pockets from the coupling interface, particularly defects located near the centre of the coupling window.

Extracorporeal shock wave lithotripsy: What is new?

OBJECTIVES

Thirty years after its introduction, extracorporeal shockwave lithotripsy (ESWL) is still first-line treatment for more than half of all urinary tract stones, but machines and treatment strategies have significantly developed over time. In this review, we summarise the latest knowledge about the clinically important aspects of ESWL.

METHODS

We searched PubMed to identify relevant reports and the latest European Association of Urology guidelines, and standard urological textbooks were consulted.

RESULTS

New technical developments include: Twin-head and tandem-pulse shock-wave generators; wide-focus, low-pressure systems; optimised coupling; and automated location and acoustic tracking systems. Indications have been refined, making possible the identification of patients in whom ESWL treatment is likely to fail. By lowering the shock-wave rate, improving coupling, applying abdominal compression, power 'ramping' and postoperative medical expulsion therapy, treatment protocols have been optimised.

CONCLUSIONS

Promising new technical developments are under development, with the potential to increase the stone-free rate after ESWL. For optimal results, the refined indications need to be respected and optimised treatment protocols should be applied.