Limitations of extracorporeal shock wave lithotripsy

Prospective Evaluation of Extracorporeal Shockwave Lithotripsy in Renal and Upper Ureteric Stone Treatment: Clinical Assessment and Results

INTRODUCTION

Extracorporeal shockwave lithotripsy (ESWL) is a widely accepted non-invasive treatment for renal and upper ureteric stones smaller than 2 cm due to its safety and efficacy. Despite advancements in minimally invasive techniques, extracorporeal shockwave lithotripsy remains an important modality.

AIMS AND OBJECTIVE

This prospective observational study aimed to evaluate the outcomes of ESWL in managing renal and upper ureteric stones measuring less than 2 cm in terms of stone clearance.

MATERIAL AND METHODS

In a study conducted at a university-affiliated tertiary care hospital, 119 patients with renal and upper ureteric stones underwent extracorporeal shockwave lithotripsy over a 12-month period. Data on patient demographics, stone characteristics, treatment procedures, and complications were collected. Follow-up assessments were performed at two-week intervals for up to two months post-treatment.

RESULTS

The mean age of patients was 39.78 years, with a mean stone size of 1.2 cm. Right kidney stones were more prevalent (61.3% [n=76]). Complications included fever (19.3% [n=23]), gross haematuria (24.3% [n=29]), and steinstrasse (21.8% [n=26]). The success rate of extracorporeal shockwave lithotripsy was 81.5% (n=97), with 18.5% (n=22) of patients requiring surgical intervention due to incomplete fragmentation or residual fragments >4 mm. Stone size and density played significant roles in treatment success.

CONCLUSION

Despite advancements in minimally invasive techniques, ESWL retains its significance as a noninvasive and effective treatment option for renal and upper ureteric stones smaller than 2 cm. Its success depends on various factors, including the stone site, size, and composition. ESWL offers advantages such as minimal morbidity, shorter hospital stays, and better patient compliance. Complications such as steinstrasse are manageable with conservative measures or ancillary procedures. While ESWL may be losing ground in some cases, its noninvasive nature and favourable outcomes make it a valuable option in the armamentarium for stone management.

Assessing Cost-Effectiveness of New Technologies in Stone Management

Diagnosis, treatment, and follow-up are all influential in determining the overall cost to the health care system for kidney stones. New innovations in the field of nephrolithiasis have been abundant, including disposable ureteroscopes, ultrasound-guided approaches to percutaneous nephrolithotomy, and advanced laser lithotripters. Identifying cost-effective treatment strategies encourages practitioners to be thoughtful about providing value-based high-quality care and remains on important principle in the treatment of urinary stone disease.

Efficacy of commercialised extracorporeal shock wave lithotripsy service: a review of 589 renal stones

BACKGROUND

Extracorporeal shockwave lithotripsy (ESWL) is the management of choice for renal stones 20 mm or smaller, with a stone clearance rate of up to 89%. The purpose of the present is to investigate the efficacy of a commercialised ESWL service, being performed as an outsourced treatment using a mobile lithotripsy system on an outpatient basis. Furthermore, the study aims to evaluate the risk of needing treatment with an internal ureteral double-J stent (JJ) after ESWL treatment.

METHODS

During an eight-year period, 461 patients with a total of 589 renal stones were treated using a mobile lithotripsy system at a single Danish institution. A commercial company performed all treatments using a Storz Modulith SLK® system. Each stone was prospectively registered according to size, intra renal location and the presence of a JJ at the time of treatment. The number of required ESWL treatments and auxiliary procedures were retrospectively evaluated.

RESULTS

The success rate after the initial ESWL procedure was 69%, which increased to an overall success rate of 93% after repeated treatment. A negative correlation was found between stone size and the overall success rate (r = -0.2, p < 0.01). The upper calyx was associated with a significantly better success rate, but otherwise intra renal stone location was not predictive for treatment success. A total of 17 patients (2.9%) required treatment with a JJ after the ESWL procedure. No significant difference was observed between the stone size or intra renal location and the risk of needing treatment with JJ after ESWL.

CONCLUSIONS

Commercialised ESWL treatment can achieve an overall success rate of more than 90% using a mobile lithotripsy system. As expected, an inverse relation between stone size and success rate was found. Patients who do not require treatment with a JJ prior to ESWL will only rarely need treatment with a JJ after ESWL, irrespective of stone size and intra renal stone location.

Ultrasonography Is Not Inferior to Fluoroscopy to Guide Extracorporeal Shock Waves during Treatment of Renal and Upper Ureteric Calculi: A Randomized Prospective Study

Objective

To investigate whether the visualization modality (ultrasound or fluoroscopy) used during shockwave lithotripsy (SWL) affects the clinical outcome in those instances where both imaging modalities are optional.

Methods

Between November 2014 and July 2016, 114 patients with radiopaque upper urinary tract calculi were randomly assigned to an ultrasound- or fluoroscopy-guided SWL group in a prospective, open-label, single-center study. A standardized SWL protocol was used. The stone-free rate and the positive outcome rate (stone-free or asymptomatic residual fragments ≤ 4 mm) were compared.

Results

The stone-free rate was 52% in the ultrasound-guided group compared to 42% in the fluoroscopy-guided group (p = 0.06) and the positive outcome rate was 79% in the ultrasound-guided group compared to 70% in the fluoroscopy-guided group (p = 0.28). These results were not significantly different but proved to be noninferior based on a Wilson confidence interval of independent proportions (noninferiority limit 10%). The mean number of SWL sessions was not significantly different (p = 0.4).

Conclusion

Our study demonstrated that the clinical results of ultrasound-guided SWL were not inferior to the results of fluoroscopy-guided SWL, while no ionizing radiation is needed.

Does Transient Cessation of Antiplatelet Medication Prior to Shock Wave Lithotripsy Have Any Safety Concern: Evaluation of the Short Term Safety Results

OBJECTIVE

The study aimed to evaluate the true safety of transient cessation of the antiplatelet medication before extracorporeal shock wave lithotripsy (SWL) on bleeding-related complications.

PATIENTS AND METHODS

Forty cases undergoing SWL for renal pelvic stones were included and depending on the use of antiplatelet medication they were divided into 2 groups namely: group 1, cases under antiplatelet medication in whom the medication was stopped before ESWL; and group 2, cases without any antiplatelet medication. Comparative evaluation of patient, stone and treatment-related parameters were done in both groups.

RESULTS

Although microscopic hematuria was present in all cases, the incidence of macroscopic hematuria was higher in cases undergoing antiplatelet medication when compared with the other cases. Regarding the microscopic hematuria again, the mean number erythrocytes per field of analysis was significantly higher in group 1 cases. The mean value of the hematoma size was similar in both groups.

CONCLUSION

Our findings indicate that SWL can be applied safely in patients under antiplatelet therapy following the cessation of medication for a certain period of time. However, among the cases treated with this concept in our study, we clearly observed that the incidence of procedure-related hematoma formation and macroscopic hematuria were more common in such cases than in the normal ones.

The Efficacy of Medical Expulsive Therapy (MET) in Improving Stone-free Rate and Stone Expulsion Time, After Extracorporeal Shock Wave Lithotripsy (SWL) for Upper Urinary Stones: A Systematic Review and Meta-analysis

In this meta-analysis, we included randomized studies on medical expulsive therapy implemented following shock wave lithotripsy for renal and ureteral stones. Pooled results demonstrated the efficacy of α-blockers, nifedipine, Rowatinex, and Uriston in increasing stone clearance. In addition, the time to stone elimination, the intensity of pain, the formation of steinstrasse, and the need for auxiliary procedures were reduced mainly with α-blockers. Expulsion rate was not correlated with the type of α-blocker, the diameter, and the location of stone. Our results show that medical expulsive therapy for residual fragments after shock wave lithotripsy should be implemented in clinical practice.

Elemental Content of Calcium Oxalate Stones from a Canine Model of Urinary Stone Disease

One of the most common types of urinary stones formed in humans and some other mammals is composed of calcium oxalate in ordered hydrated crystals. Many studies have reported a range of metals other than calcium in human stones, but few have looked at stones from animal models such as the dog. Therefore, we determined the elemental profile of canine calcium oxalate urinary stones and compared it to reported values from human stones. The content of 19 elements spanning 7-orders of magnitude was quantified in calcium oxalate stones from 53 dogs. The elemental profile of the canine stones was highly overlapping with human stones, indicating similar inorganic composition. Correlation and cluster analysis was then performed on the elemental profile from canine stones to evaluate associations between the elements and test for potential subgrouping based on elemental content. No correlations were observed with the most abundant metal calcium. However, magnesium and sulfur content correlated with the mineral hydration form, while phosphorous and zinc content correlated with the neuter status of the dog. Inter-elemental correlation analysis indicated strong associations between barium, phosphorous, and zinc content. Additionally, cluster analysis revealed subgroups within the stones that were also based primarily on barium, phosphorous, and zinc. These data support the use of the dog as a model to study the effects of trace metal homeostasis in urinary stone disease.

Comparison of extracorporeal shock wave lithotripsy running models between outsourcing cooperation and rental cooperation conducted in Taiwan

BACKGROUND/PURPOSE

We conducted a retrospective study to compare the cost and effectiveness between two different running models for extracorporeal shock wave lithotripsy (SWL), including the outsourcing cooperation model (OC) and the rental cooperation model (RC).

METHODS

Between January 1999 and December 2005, we implemented OC for the SWL, and from January 2006 to October 2011, RC was utilized. With OC, the cooperative company provided a machine and shared a variable payment with the hospital, according to treatment sessions. With RC, the cooperative company provided a machine and received a fixed rent from the hospital. We calculated the cost of each treatment session, and evaluated the break-even point to estimate the lowest number of treatment sessions to make the balance between revenue and cost every month. Effectiveness parameters, including the stone-free rate, the retreatment rate, the rate of additional procedures and complications, were evaluated.

RESULTS

Compared with OC there were significantly less treatment sessions for RC every month (42.6±7.8 vs. 36.8±6.5, p=0.01). The cost of each treatment session was significantly higher for OC than for RC (751.6±20.0 USD vs. 684.7±16.7 USD, p=0.01). The break-even point for the hospital was 27.5 treatment sessions/month for OC, when the hospital obtained 40% of the payment, and it could be reduced if the hospital got a greater percentage. The break-even point for the hospital was 27.3 treatment sessions/month for RC. No significant differences were noticed for the stone-free rate, the retreatment rate, the rate of additional procedures and complications.

CONCLUSION

Our study revealed that RC had a lower cost for every treatment session, and fewer treatment sessions of SWL/month than OC. The study might provide a managerial implication for healthcare organization managers, when they face a situation of high price equipment investment.

Recent finding and new technologies in nephrolitiasis: a review of the recent literature

This review summarizes recent literature on advances regarding renal and ureteral calculi, with particular focus in areas of recent advances in the overall field of urolithiasis. Clinical management in everyday practice requires a complete understanding of the issues regarding metabolic evaluation and subgrouping of stone-forming patients, diagnostic procedures, effective treatment regime in acute stone colic, medical expulsive therapy, and active stone removal. In this review we focus on new perspectives in managing nephrolitihiasis and discuss recentadvances, including medical expulsive therapy, new technologies, and refinements of classical therapy such as shock wave lithotripsy, give a fundamental modification of nephrolithiasis management. Overall, this field appears to be the most promising, capable of new developments in ureterorenoscopy and percutaneous approaches. Further improvements are expected from robotic-assisted procedures, such as flexible robotics in ureterorenoscopy.

Impact of stone disease: chronic kidney disease and quality of life

This article reviews the impact of stone disease on chronic kidney disease and renal function; evaluating the natural progression of disease as well as the impact of surgical interventions. The impact of stone disease, medical therapy, and surgical therapy for stones on quality of life is discussed.

Ureteroscopic treatment of larger renal calculi (>2 cm)

Objectives

To evaluate the current status of ureteroscopic lithotripsy (UL) for treating renal calculi of >2 cm, as advances in flexible ureteroscope design, accessory instrumentation and lithotrites have revolutionised the treatment of urinary calculi. While previously reserved for ureteric and small renal calculi, UL has gained an increasing role in the selective management of larger renal stone burdens.

Methods

We searched the available databases, including PubMed, Google Scholar, and Scopus, for relevant reports in English, and the article bibliographies to identify additional relevant articles. Keywords included ureteroscopy, lithotripsy, renal calculi, and calculi >2 cm. Retrieved articles were reviewed to consider the number of patients, mean stone size, success rates, indications and complications.

Results

In all, nine studies (417 patients) were eligible for inclusion. After one, two or three procedures the mean (range) success rates were 68.2 (23–84)%, 87.1 (79–91)% and 94.4 (90.1–96.7)%, respectively. Overall, the success rate was >90% with a mean of 1.2–2.3 procedures per patient. The overall complication rate was 10.3%, including six (1.4%) intraoperative and 37 (8.9%) postoperative complications, most of which were minor. The most common indications for UL were a failed previous treatment (46%), comorbidities (18.2%), and technical and anatomical factors (12.3%).

Conclusions

UL is safe and effective for treating large renal calculi. While several procedures might be required for total stone clearance, UL should be considered a standard approach in the urologist’s options treating renal calculi of >2 cm.

Management of Clinically Insignificant Residual Fragments following Shock Wave Lithotripsy

Clinically insignificant residual fragments (CIRFs) are small fragments (less than 5 mm) that are present in upper urinary tract at the time of regular post-SWL followup. The term is controversial because they may remain silent and asymptomatic or become a risk factor for stone growth and recurrence, leading to symptomatic events, and need further urologic treatment. Although a stone-free state is the desired outcome of surgical treatment of urolithiasis, the authors believe that the presence of noninfected, nonobstructive, asymptomatic residual fragments can be managed metabolically in order to prevent stone growth and recurrence. Further urologic intervention is warranted if clinical indications for stone removal are present.

Assessment of stone composition in the management of urinary stones

Several explanations have been suggested to account for the failure of extracorporeal shockwave lithotripsy (ESWL) treatment in patients with urinary stones, including large stone volume, unfavorable stone location or composition and the type of lithotriptor used. Unfavorable stone composition is considered a major cause of failure of ESWL treatment, and consequently knowledge of the stone composition before treatment is initiated is desirable. Plain abdominal radiographs cannot accurately determine either stone composition or fragility, and although the CT attenuation value in Hounsfield units (HU) (that is, normalized to the attenuation characteristics of water) is useful, this parameter has limited value as a predictor of stone composition or the response to ESWL treatment. By contrast, stone morphology as visualized by CT correlates well with both fragility and susceptibility to fragmentation by ESWL. For patients prone to recurrent calculi, analyses of stone composition are especially important, as they may reveal an underlying metabolic abnormality. The development of advanced imaging technologies that can predict stone fragility is essential, as they could provide extra information for physicians, enabling them to select the most appropriate treatment option for patients with urinary stones.

Viscero-visceral hyperalgesia: characterization in different clinical models

Co-existing algogenic conditions in two internal organs in the same patient may mutually enhance pain symptoms (viscero-visceral hyperalgesia). The present study assessed this phenomenon in different models of visceral interaction. In a prospective evaluation, patients with: (a) coronary artery disease (CAD)+gallstone (Gs) (common sensory projection: T5); (b) irritable bowel syndrome (IBS)+dysmenorrhea (Dys) (T10-L1); (c) dysmenorrhea/endometriosis+urinary calculosis (Cal)(T10-L1); and (d) gallstone+left urinary calculosis (Gs+LCal) (unknown common projection) were compared with patients with CAD, Gs, IBS, Dys or Cal only, for spontaneous symptoms (number/intensity of pain episodes) over comparable time periods and for referred symptoms (muscle hyperalgesia; pressure/electrical pain thresholds) from each visceral location. In patients' subgroups, symptoms were also re-assessed after treatment of each condition or after no treatment. (a) CAD+Gs presented more numerous/intense angina/biliary episodes and more referred muscle chest/abdominal hyperalgesia than CAD or Gs; cardiac revascularization or cholecystectomy also reduced biliary or cardiac symptoms, respectively (0.001<p<0.05). (b) IBS+Dys had more intestinal/menstrual pain and abdomino/pelvic muscle hyperalgesia than IBS or Dys; hormonal dysmenorrhea treatment also reduced IBS symptoms; IBS dietary treatment also improved dysmenorrhea (0.001<p<0.05) while no treatment of either conditions resulted in no improvement in time of symptoms from both. (c) Cal+Dys had more urinary/menstrual pain and referred lumbar/abdominal hyperalgesia than Cal or Dys; hormonal dysmenorrhea treatment/laser treatment for endometriosis also improved urinary symptoms; lithotripsy for urinary stone also reduced menstrual symptoms (0.001<p<0.05). (d) In Gs+LCal, cholecystectomy or urinary lithotripsy did not improve urinary or biliary symptoms, respectively. Mechanisms of viscero-visceral hyperalgesia between organs with documented partially common sensory projection probably involve sensitization of viscero-viscero-somatic convergent neurons.

Comparative analysis of upper ureteral stones (> 15 mm) treated with retroperitoneoscopic ureterolithotomy and ureteroscopic pneumatic lithotripsy

OBJECTIVE

To investigate an appropriate treatment for patients with upper ureteral stones, > 15 mm in size, by comparing the therapeutic outcomes for those undergoing retroperitoneoscopic ureterolithotomy (RPUL) and rigid ureteroscopic pneumatic lithotripsy (URSPL) retrospectively.

PATIENTS AND METHODS

During the study period, 81 patients with a large upper ureteral stone (> 15 mm) were divided into two groups. RPUL was performed with retroperitoneal approach, and the stone was removed in group A. URSPL was conducted using a rigid ureteroscope, and pneumatic probe was used for lithotripsy in group B. The patient characteristics, success rate, stone-free rate, operation time, and complications were analyzed prospectively in the two groups.

RESULTS

The success rates of operation were 94.5% (34/36) in group A and 88.8% (40/45) in group B, but there were no significant differences between two groups (P > 0.05). After 4 weeks of follow-up, the stone-free rate after RPUL (100%, 34/34) and URSPL (77.5%, 31/40) groups were statistically different (P = 0.006). Furthermore, simultaneous ureterolithotomy and ureteroplasty by retroperitoneal laparoscopic surgery were performed on four patients combined with ureteral stricture. However, the mean operation time and hospital staying time after surgery in group A were longer than that in group B, and the differences were statistically significant (P < 0.05). The complication rate after RPUL (17.6%, 6/34) was lower than that after URSPL (20%, 8/40), but the differences were not statistically significant (P > 0.05).

CONCLUSION

RPUL is a safe and effective treatment technique for large, impacted, upper ureteral stones >15 mm in size when first-line treatments have failed or are unlikely to be effective. It can handle with combined pathologies simultaneously.

Complications and outcomes following extracorporeal shock wave lithotripsy: a prospective study of 3,241 patients

Extracorporeal shock wave lithotripsy (SWL) has become the least invasive treatment modality with high success rates for urinary calculi; however, its established efficacy has been associated with a number of side effects and complications. This study sought to further evaluate the incidence rate and management of the post-SWL complications and also the efficiency of procedure in a large scale of patients. During a 51-month period, 3,241 consecutive adult patients with the mean age of 38.1 years (range 15-75) and urinary calculi (>or=4 mm) underwent SWL at our referral center and were followed for 3 months prospectively. Overall, 3,614 stones [kidneys (83.5%), ureters (15.8%) and bladder (0.7%)] in 3,241 patients were treated requiring 7,245 SWL sessions. Stone-free state occurred in 71.5% calculi and success rate in 79.8% patients. The re-treatment was necessary in 37.2% patients. Auxiliary procedure and efficiency quotient were 5.6% and 0.50, respectively. SWL success rate decreased as the stone size increased (P < 0.0001). The stone-free rate was correlated with the location of the stone. During the study period, 4,075 complications occurred in our patients. Colicky pain (40%) was the most frequent symptom followed by gross hematuria (32%) and steinstrasse (24.2%). Symptomatic bacteriuria developed in 9.7% patients; Escherichia coli (30.4%) was the most causative organism. In conclusion, the complication rate following SWL was high in our study; however, the majority was mild and managed conservatively or with the minimal intervention. Moreover, the management of urinary calculi in adults using SWL was proved to be safe and efficient, particularly for ureteral stones <10 mm, renal pelvic stones <20 mm, and bladder stones <30 mm.

Chronic kidney disease affects the stone-free rate after extracorporeal shock wave lithotripsy for proximal ureteric stones

OBJECTIVE

To investigate the effect of renal function on the stone-free rate (SFR) of proximal ureteric stones (PUS) after extracorporeal shock wave lithotripsy (ESWL), as urinary obstruction caused by PUS can impair renal function, and elevated serum creatinine levels are associated with decreased ureteric stone passage.

PATIENTS AND METHODS

From January 2005 to December 2007, 1534 patients had ESWL for urolithiasis, 319 having ESWL in situ for PUS; they were reviewed retrospectively. Patients requiring simultaneous treatment of kidney stones, placement of a double pigtail stent, or percutaneous pigtail nephrostomy tube were excluded. We divided patients into groups by chronic kidney disease (CKD) stage according to the estimated glomerular filtration rate (eGFR) of ≥ 60 and <60 mL/min/1.73 m(2). Stone-free status was defined as no visible stone fragments on a plain abdominal film at 3 months after ESWL. A logistic regression model was used to evaluate the possible significant factors that influenced the SFR of PUS after ESWL, and to develop a prediction model.

RESULTS

The overall SFR of PUS (276/319 patients) was 86.5%; the SFR was 93% in patients with an eGFR of ≥ 60 and 50% in those with an eGFR of <60 (P < 0.001). After univariate and multivariate analysis, the three significant factors affecting SFR were an eGFR of ≥ 60, stone width, and gender, with odds ratios (95% confidence intervals) of 19.54 (8.25-46.30) (P < 0.001), 0.67 (0.55-0.82) (P < 0.001) and 0.16 (0.05-0.50 (P = 0.002), respectively. A logistic regression model was developed to estimate the probability of SFR after ESWL, the equation being 1/(1 + exp [-(3.8137 - 0.3967 × (stone width) + 2.9724 × eGFR - 1.8120 × Male)]), where stone width is the observed value (mm), eGFR = 1 for eGFR ≥ 60 and 0 for <60, and male = 1 for male, 0 for female.

CONCLUSIONS

Gender, eGFR ≥ 60 and a stone width of >7 mm were significant predictors affecting the SFR after one session of ESWL for PUS.

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.

Comparison of two different running models for the shock wave lithotripsy machine in Taipei City Hospital: self-support versus outsourcing cooperation

To compare two different running models including self-support and outsourcing cooperation for the extracorporeal shock wave lithotripsy (SWL) machine in Taipei City Hospital, we made a retrospective study. Self-support means that the hospital has to buy an SWL machine and get all the payment from SWL. In outsourcing cooperation, the cooperative company provides an SWL machine and shares the payment with the hospital. Between January 2002 and December 2006, we used self-support for the SWL machine, and from January 2007 to December 2008, we used outsourcing cooperation. We used the method of full costing to calculate the cost of SWL, and the break-even point was the lowest number of treatment sessions of SWL to make balance of payments every month. Quality parameters including stone-free rate, retreatment rate, additional procedures and complication rate were evaluated. When outsourcing cooperation was used, there were significantly more treatment sessions of SWL every month than when utilizing self-support (36.3 +/- 5.1 vs. 48.1 +/- 8.4, P = 0.03). The cost of SWL for every treatment session was significantly higher using self-support than with outsourcing cooperation (25027.5 +/- 1789.8 NT$ vs. 21367.4 +/- 201.0 NT$). The break-even point was 28.3 (treatment sessions) for self-support, and 28.4 for outsourcing cooperation, when the hospital got 40% of the payment, which would decrease if the percentage increased. No significant differences were noticed for stone-free rate, retreatment rate, additional procedures and complication rate of SWL between the two running models. Besides, outsourcing cooperation had lower cost (every treatment session), but a greater number of treatment sessions of SWL every month than self-support.

A passive acoustic device for real-time monitoring of the efficacy of shockwave lithotripsy treatment

Extracorporeal shockwave lithotripsy (ESWL) is the preferred modality for the treatment of renal and ureteric stone disease. Currently X-ray or ultrasound B-scan imaging are used to locate the stone and to check that it remains targeted at the focus of the lithotripter during treatment. Neither imaging modality is particularly effective in allowing the efficacy of treatment to be judged during the treatment session. A new device is described that, when placed on the patient's skin, can passively monitor the acoustic signals that propagate through the body after each lithotripter shock, and which can provide useful information on the effectiveness of targeting. These acoustic time histories are analyzed in real time to extract the two main characteristic peak amplitudes (m(1) and m(2)) and the time between these peaks (t(c)). A set of rules based on the acoustic parameters was developed during a clinical study in which a complete set of acoustic and clinical data was obtained for 30 of the 118 subjects recruited. The rules, which complied with earlier computational fluid dynamics (CFD) modeling and in vitro tests, allow each shock to be classified as "effective" or "ineffective." These clinically-derived rules were then applied in a second clinical study in which complete datasets were obtained for 49 of the 85 subjects recruited. This second clinical study demonstrated almost perfect agreement (kappa = 0.94) between the number of successful treatments, defined as >50% fragmentation as determined by X-ray at the follow-up appointment, and a device-derived global treatment score, TS(0), a figure derived from the total number of effective shocks in any treatment. The acoustic system is shown to provide a test of the success of the treatment that has a sensitivity of 91.7% and a specificity of 100%. In addition to the predictive capability, the device provides valuable real-time feedback to the lithotripter operator by indicating the effectiveness of each shock, plus an indication TS(t) of the cumulative effectiveness of the shocks given so far in any treatment, and trends in key parameters. This feedback would allow targeting adjustments to be made during treatment. An example is given of its application to mistargeting because of respiration.

The concentration of Zn, Mg and Mn in calcium oxalate monohydrate stones appears to interfere with their fragility in ESWL therapy

Extracorporeal shockwave lithotripsy (SWL) has remained the preferred method of treatment of urinary stones since its introduction in 1980. Although SWL is classified as a potential first-line treatment for renal stones smaller than 2 cm and its overall success rate is higher than 85% for stone clearance, not all renal calculi are successfully fragmented after SWL. Among the urinary stones, calcium oxalate monohydrate (COM) stone is one of the hardest stones to fragment. Several factors interfering with stone fragility are known to exist. In addition to technical properties for SWL to increase the quality and rate of stone disintegration, the composition of stones such as trace element levels may also interfere with the efficacy of SWL. Therefore, in the present study, we aimed to elucidate the correlation, if it exists, between fragmentation of renal stones and their trace element (Cu, Zn, Mg, Fe, Pb, Mn, Cr) concentrations. For this purpose, the patients admitted to our department who were identified with urinary stones (740 patients) and underwent SWL sessions were evaluated prospectively. Patients having 5-20 mm of solitary COM stone in the renal pelvis were included in this study. The trace element concentrations of renal stones that were successfully fragmented with SWL (SWL-S) were compared with those that were unsuccessfully fragmented after three SWL sessions (SWL-US) and removed surgically. Our measurements showed that the concentrations of Cu, Fe, Pb, and Cr were similar in both groups; by contrast, the concentration of Zn, Mg and Mn was significantly lower in SWL-US renal stones. The present results suggest that low concentrations of Zn, Mg and Mn in COM stones appear to make them resistant to SWL fragmentation and may offer a critical distinction for the choice of a treatment program.