Storz Medical Lithotripsy Index Predicts Success of Shock Wave Lithotripsy in Ureteric Stones.

PURPOSE: The aim of this study is to evaluate the factors affecting treatment success in patients who underwent Shock wave lithotripsy (SWL) for ureter stones and to investigate the effect of Storz Medical Lithotripsy Index (SMLI) on treatment effectiveness in ureteric stones. METHOD: Prospective data were collected on patients undergoing SWL treatment for ureter stones between January 2013 and May 2021. Stone location, number, and size were determined with Non contrast CT (NCCT) for all patients. All patients underwent SWL with a Storz Modulith SLK lithotripsy machine with local anaesthesia. The total amount of energy applied to the stone was calculated using the Storz Medical Lithotripsy Index (SMLI). All patients were evaluated for stone-free status by X-ray at least 2 weeks after treatment. The success of the procedure was defined as the patient being completely stone free (SF) or detection of residual fragments < 4 mm that did not require further treatment Results: A total of 1199 patients with ureter stones were included in the study. The mean age of the patients was 43.11 ± 10.65 (18-73), and the mean BMI was 27.87±8.12(19.02-38.65). During SWL, 89.3% of patients demonstrated excellent pain tolerance (1070/1199). A total of 119 patients could not tolerate pain during SWL (10.7%). Treatment success was associated with fewer treatment sessions (2.04±1.64 vs. 2.50 ± 1.48; p < 0.001), smaller stone size (7.35±2.99 vs. 9.02 ± 3.81; p < 0.001) and higher SMLI/stone size (29.70 ± 17.48 vs. 24.98±16.01; p < 0.001). In the univariate and multivariate regression analysis, the factors affecting the success of the treatment were the number of sessions (OR: 1.147), stone size (OR: 1.112), SMLI/stone size (OR: 1.115) and pain tolerance (OR: 0.740). CONCLUSION: In the treatment of ureteral stones with SWL, number of sessions, stone size, SMLI/stone size, and pain tolerance are the factors affecting success. SMLI per stone size is a statistically significant factor for predicting SWL success.

An analysis of stone management over the decade before the COVID-19 pandemic in Germany, France and England.

OBJECTIVES: To understand the implications that the rising upper urinary tract (UUT) stone prevalence in Europe and the increasing burden places on patients and healthcare providers (HCPs), we investigated the evolution of diagnoses and procedures in Germany, France and England over the decade before the coronavirus disease 2019 (COVID-19) pandemic. METHODS: We identified International Classification of Diseases (ICD)-10 codes related to UUT stones diagnosis and extracted procedure volumes for extracorporeal shockwave lithotripsy (ESWL), ureteroscopy (URS), percutaneous nephrolithotomy and open surgery using national procedure codes from the German Institute for the Hospital Remuneration System, the French Technical Agency of Hospitalisation Information and NHS England Hospital Episode Statistics. We analysed procedures vs hospital diagnoses from 2010 to 2019 and reported results per 100 000 inhabitants. RESULTS: Between 2010 and 2019, ICD-10 N20 codes for calculus of kidney and ureter increased by 8%, 26% and 15% in Germany, France, and England respectively; whereas procedures increased by 3%, 38% and 18%. Of the patients diagnosed with stones, the percentage that received treatment (of any type) differed between countries. In 2019, in Germany 83% of patients diagnosed with stones received treatment, in France 88%, and in England 56%. These figures were relatively stable over the 10-year study period. Over the past decade, the dominant procedure shifted from ESWL to URS, and the average length of stay for URS decreased. Day case procedures increased in France and England (by 68% and 23%), no data were available in Germany. CONCLUSION: This analysis highlights an increase in stone diagnoses and procedures, and a shift of surgical management. This development may be due to clinical advantages and advanced technology. The continued stone prevalence rise affects patients, hospitals, and HCPs.

The New Lithotripsy Index predicts success of shock wave lithotripsy.

AIM: The aim of this study is to evaluate the factors affecting treatment success in patients who underwent Shock wave lithotripsy (SWL) and to investigate the effect of the Storz Medical Lithotripsy Index (SMLI) on treatment effectiveness. METHODS: Prospective data were collected on patients undergoing SWL treatment for kidney stones between January 2013 and May 2021. Stone location, number and size were determined with non-contrast CT (NCCT) for all patients. All patients underwent SWL with a Storz Modulith SLK lithotripsy machine without anaesthesia. The total amount of energy applied to the stone was calculated using the SMLI. All patients were evaluated for stone-free status by X-ray at least 2 weeks after treatment. The success of the procedure was defined as the patient being completely stone free or the detection of residual fragments < 4 mm that did not require further treatment. RESULTS: A total of 1230 patients with kidney stones were included in the study. The mean age of the patients was 42.33 ± 11.78 (18-75), and the mean BMI was 28.47 ± 8.78 (19.25-38.52). During SWL, 75.6% of patients demonstrated excellent pain tolerance (930/1230). A total of 116 patients could not tolerate the pain during SWL (9.4%). Treatment success was associated with fewer treatment sessions (2.34 ± 1.75 vs. 2.90 ± 2.04; p < 0.001), smaller stone size (7.52 ± 3.29 vs 8.60 ± 3.93; p < 0.001) and higher SMLI/stone size (25.11 ± 13.63 vs. 22.27 ± 14.50; p < 0.001). In the univariate and multivariate regression analysis, the factors affecting the success of the treatment were the number of sessions (OR 1.170), stone size (OR 1.142), number of shocks (OR 1.005), SMLI/stone size (OR 1.024) and pain tolerance (OR 0.692). CONCLUSION: In the treatment of kidney stones with SWL, stone site, stone size, SMLI/stone size, and pain tolerance are the factors affecting success. SMLI per stone size is a statistically significant factor for predicting SWL success.

Utility of blood tests in screening for metabolic disorders in kidney stone disease.

OBJECTIVES: To determine the clinical utility of blood tests as a screening tool for metabolic abnormalities in patients with kidney stone disease. SUBJECTS AND METHODS: Clinical and biochemical data from 709 patients attending the Oxford University Hospitals NHS Foundation Trust for assessment and treatment of kidney stones were prospectively collected between April 2011 and February 2017. Data were analysed to determine the utility of serum calcium, parathyroid hormone (PTH), urate, chloride, bicarbonate, potassium and phosphate assays in screening for primary hyperparathyroidism, normocalcaemic hyperparathyroidism, hyperuricosuria, distal renal tubular acidosis (dRTA) and hypercalciuria. RESULTS: An elevated serum calcium level was detected in 2.3% of patients. Further investigations prompted by this finding resulted in a diagnosis of primary hyperparathyroidism in 0.2% of men and 4.6% of women for whom serum calcium was recorded. An elevated serum PTH level in the absence of hypercalcaemia was detected in 15.1% of patients. Of these patients, 74.6% were vitamin D-insufficient; no patients were diagnosed with normocalcaemic hyperparathyroidism. Hyperuricosuria was present in 21.6% of patients and hypercalciuria in 47.1%. Hyperuricaemia was not associated with hyperuricosuria, nor was hypophosphataemia associated with hypercalciuria. No patient was highlighted as being at risk of dRTA using serum chloride and bicarbonate as screening tests. CONCLUSION: This study indicates that individuals presenting with renal calculi should undergo metabolic screening with a serum calcium measurement alone. Use of additional blood tests to screen for metabolic disorders is not cost-effective and may provide false reassurance that metabolic abnormalities are not present. A full metabolic assessment with 24-h urine collection should be undertaken in recurrent stone formers and in those at high risk of future stone disease to identify potentially treatable metabolic abnormalities.

Genetic variants of calcium and vitamin D metabolism in kidney stone disease.

Kidney stone disease (nephrolithiasis) is a major clinical and economic health burden with a heritability of ~45-60%. We present genome-wide association studies in British and Japanese populations and a trans-ethnic meta-analysis that include 12,123 cases and 417,378 controls, and identify 20 nephrolithiasis-associated loci, seven of which are previously unreported. A CYP24A1 locus is predicted to affect vitamin D metabolism and five loci, DGKD, DGKH, WDR72, GPIC1, and BCR, are predicted to influence calcium-sensing receptor (CaSR) signaling. In a validation cohort of only nephrolithiasis patients, the CYP24A1-associated locus correlates with serum calcium concentration and a number of nephrolithiasis episodes while the DGKD-associated locus correlates with urinary calcium excretion. In vitro, DGKD knockdown impairs CaSR-signal transduction, an effect rectified with the calcimimetic cinacalcet. Our findings indicate that studies of genotype-guided precision-medicine approaches, including withholding vitamin D supplementation and targeting vitamin D activation or CaSR-signaling pathways in patients with recurrent kidney stones, are warranted.

Predicting shockwave lithotripsy outcome for urolithiasis using clinical and stone computed tomography texture analysis variables.

We aimed to develop and evaluate a statistical model, which included known pre-treatment factors and new computed tomography texture analysis (CTTA) variables, for its ability to predict the likelihood of a successful outcome after extracorporeal shockwave lithotripsy (SWL) treatment for renal and ureteric stones. Up to half of patients undergoing SWL may fail treatment. Better prediction of which cases will likely succeed SWL will help patients to make an informed decision on the most effective treatment modality for their stone. 19 pre-treatment factors for SWL success, including 6 CTTA variables, were collected from 459 SWL cases at a single centre. Univariate and multivariable analyses were performed by independent statisticians to predict the probability of a stone free (both with and without residual fragments) outcome after SWL. A multivariable model had an overall accuracy of 66% on Receiver Operator Curve (ROC) analysis to predict for successful SWL outcome. The variables most frequently chosen for the model were those which represented stone size. Although previous studies have suggested SWL can be reliably predicted using pre-treatment factors and that analysis of CT stone images may improve outcome prediction, the results from this study have not produced a useful model for SWL outcome prediction.

Impact of Case Volume on Shock Wave Lithotripsy Outcomes: Data from the National Shock Wave Lithotripsy Database of New Zealand.

Purpose: To assess the impact of individual operator case volume on shock wave lithotripsy (SWL) treatment outcomes in more than 9000 stone cases over a 20-year period in New Zealand. Materials and Methods: Stone cases treated with SWL on the Mobile Medical Technology (MMT) vehicle between June 19, 1995, and December 1, 2014, were identified. Data collection was undertaken prospectively for patient, stone, and treatment characteristics, and retrospectively for treatment outcomes. Multivariate analysis using binary logistic regression was undertaken to assess whether radiographer stone case volume (stones/year) was an independent predictor of SWL success (stone free or clinically insignificant residual fragments ≤4 mm at follow-up). Results: Sixteen radiographers delivered treatment to the included cohort (9039 stone cases), with a median case volume (stones/year) of 73 (range: 37-197) and median total of 425 stones treated (range: 71-1721). The two radiographers with highest case volumes achieved the highest success rates. Radiographer case volume (stones/year) was independently associated with SWL success (odds ratio [OR]: 1.004, 95% confidence interval [CI]: 1.003-1.005, p < 0.0001) and reduced need for post-SWL hospital admission (OR: 0.997, 95% CI: 0.994-1.000, p = 0.028), but there was no associated decrease in post-SWL urosepsis (OR: 0.999, 95% CI: 0.974-1.025, p = 0.941), perinephric hematoma (OR: 1.003, 95% CI: 0.985-1.020, p = 0.778), or need for auxiliary procedures (OR: 1.000, 95% CI: 0.998-1.002, p = 0.871). Conclusions: SWL success rates can be improved by increasing the frequency of cases performed by individual operators. In this multicenter cohort of more than 9000 stone cases treated over a 20-year period, the best outcomes were seen for those radiographers performing >150 cases per year.

The Fluid Mechanics of Ureteroscope Irrigation.

PURPOSE: To develop a physical understanding of ureterorenoscopy irrigation, we derive mathematical models from basic physical principles and compare these predictions with the results of benchtop experiments. Mathematical modeling can be used to understand the role of inlet pressure, tip deflection, the presence of working tools, geometric properties of the instruments used, and material properties of the irrigation fluid on resulting flow rate. MATERIALS AND METHODS: We develop theoretical models to describe irrigation flow in an idealized setup and compare with benchtop experiments for flow through a straight scope, a scope with a deflected tip, and a scope with a working tool inserted. The benchtop experiments were performed using Boston Scientific LithoVue ureteroscope and a variety of Boston Scientific working tools. Standard ureteroscope working channels have circular cross sections, but using theoretical models we investigate whether modifications to the cross-sectional geometry can enhance flow rates. RESULTS: The theoretical flow predictions are confirmed by experimental results. Tip deflection is shown to have a negligible effect on flow rate, but the presence of working tools decreases flow significantly (for a fixed driving pressure). Flow rate is predicted to improve when tools are placed at the edge of the channel, rather than the center, and modifying the cross-sectional shape from a circle to an ellipse can further increase flow rate. CONCLUSIONS: A mathematical framework is formulated and shown to accurately predict the properties of ureteroscope irrigation flow. The theoretical approach has significant potential in quantifying irrigation flow and improving ureteroscope design.

A Drosophila genetic model of nephrolithiasis: transcriptional changes in response to diet induced stone formation.

BACKGROUND: Urolithiasis is a significant healthcare issue but the pathophysiology of stone disease remains poorly understood. Drosophila Malpighian tubules were known to share similar physiological function to human renal tubules. We have used Drosophila as a genetic model to study the transcriptional response to stone formation secondary to dietary manipulation. METHODS: Wild-type male flies were raised on standard medium supplemented with lithogenic agents: control, sodium oxalate (NaOx) and ethylene glycol (EG). At 2 weeks, Malpighian tubules were dissected under polarized microscope to visualize crystals. The parallel group was dissected for RNA extraction and subsequent next-generation RNA sequencing. RESULTS: Crystal formation was visualized in 20%(±2.2) of flies on control diet, 73%(±3.6) on NaOx diet and 84%(±2.2) on EG diet. Differentially expressed genes were identified in flies fed with NaOx and EG diet comparing with the control group. Fifty-eight genes were differentially expressed (FDR <0.05, p < 0.05) in NaOx diet and 20 genes in EG diet. The molecular function of differentially expressed genes were assessed. Among these, Nervana 3, Eaat1 (Excitatory amino acid transporter 1), CG7912, CG5404, CG3036 worked as ion transmembrane transporters, which were possibly involved in stone pathogenesis. CONCLUSIONS: We have shown that by dietary modification, stone formation can be manipulated and visualized in Drosophila Malpighian tubules. This genetic model could be potentially used to identify the candidate genes that influence stone risk hence providing more insight to the pathogenesis of human stone disease.

The Preoperative Assessment and Optimization of Patients Undergoing Major Urological Surgery.

PURPOSE OF REVIEW: Improving patient outcomes from major urological surgery requires not only advancement in surgical technique and technology, but also the practice of patient-centered, multidisciplinary, and integrated medical care of these patients from the moment of contemplation of surgery until full recovery. This review examines the evidence for recent developments in preoperative assessment and optimization that is of relevance to major urological surgery. RECENT FINDINGS: Current perioperative medicine recommendations aim to improve the short-term safety and long-term effectiveness of surgical treatments by the delivery of multidisciplinary integrated medical care. New strategies to deliver this aim include preoperative risk stratification using a frailty index and cardiopulmonary exercise testing for patients undergoing intra-abdominal surgery (including radical cystectomy), preoperative management of iron deficiency and anemia, and preoperative exercise intervention. Proof of the utility and validity for improving surgical outcomes through advances in preoperative care is still evolving. Evidence-based developments in this field are likely to benefit patients undergoing major urological surgery, but further research targeted at high-risk patients undergoing specific urological operations is required.

CT Texture Analysis of Ex Vivo Renal Stones Predicts Ease of Fragmentation with Shockwave Lithotripsy.

INTRODUCTION: Understanding the factors affecting success of extracorporeal shockwave lithotripsy (SWL) would improve informed decision-making on the most appropriate treatment modality for an individual patient. Although stone size and skin-to-stone distance do correlate with fragmentation efficacy, it has been shown that stone composition and architecture, as reflected by structural heterogeneity on CT, are also important factors. This study aims to determine if CT texture analysis (CTTA), a novel, nondestructive, and objective tool that generates statistical metrics reflecting stone heterogeneity, could have utility in predicting likelihood of SWL success. MATERIALS AND METHODS: Seven spontaneously passed, intact renal tract stones, were scanned ex vivo using standard CT KUB and micro-CT. The stones were then fragmented in vitro using a clinical lithotripter, after which, chemical composition analysis was performed. CTTA was used to generate a number of metrics that were correlated to the number of shocks needed to fragment the stone. RESULTS: CTTA metrics reflected stone characteristics and composition, and predicted ease of SWL fragmentation. The strongest correlation with number of shocks required to fragment the stone was mean Hounsfield unit (HU) density (r = 0.806, p = 0.028) and a CTTA metric measuring the entropy of the pixel distribution of the stone image (r = 0.804, p = 0.039). Using multiple linear regression analysis, the best model showed that CTTA metrics of entropy and kurtosis could predict 92% of the outcome of number of shocks needed to fragment the stone. This was superior to using stone volume or density. CONCLUSIONS: CTTA metrics entropy and kurtosis have been shown in this experimental ex vivo setting to strongly predict fragmentation by SWL. This warrants further investigation in a larger clinical study for the contribution of CT textural metrics as a measure of stone heterogeneity, along with other known clinical factors, to predict likelihood of SWL success.

Management of iatrogenic ureteric injury with retrograde ureteric stenting: an analysis of factors affecting technical success and long-term outcome.

Background Iatrogenic ureteral injuries arise as serious complication following obstetrics, gynecological, general, and urological surgery with incidence in the range of 0.5-10%. Retrograde placement of double-J ureteric stent is a possible treatment option if the injury is not recognized at the time of surgery. Purpose To assess technical success and long-term outcome associated with retrograde ureteric stent insertion for iatrogenic ureteric injury. Material and Methods Between 1999 and 2011, 26 patients with initially unrecognized iatrogenic ureteric injury underwent initial management with retrograde ureteric stenting. Full case-notes were available for review in 25 patients. Results The mean interval from injury to attempted stenting was 19.4 days. Successful retrograde ureteric stenting was achieved in 21/25 patients (81%). Retrograde stenting failed in four patients, and nephrostomy followed by alternative procedures were performed instead. At a median follow-up interval of 9.7 months, normal anatomy was demonstrated on 12/21 patients (57%) and a stricture was observed in 6/21 patients (28%) with three requiring surgical intervention. Conclusion Retrograde stenting is a safe and efficient initial management in patients with iatrogenic ureteric injuries.

Tracking kidney stones in a homogeneous medium using a trilateration approach.

Shock wave lithotripsy is a non-invasive procedure by which kidney stones are fragmented by thousands of shock waves. Currently, many shock waves are delivered to the body that do not impact the stone, but do result in tissue trauma. This motivates developing a monitoring system to locate kidney stones, with the goal of gating shock waves not aligned with the stone, and hence, reducing renal trauma during lithotripsy. The system consists of a circular array housing twenty-two 0.5 MHz transducers that can be mounted on a clinical lithotripter. It was deployed in a water tank and tested with two stone models made from gypsum cement and a stone model fragment. An algorithm consisting of threshold detection, automatic rejection of weak signals, and triangulation was developed to determine the location of stones. The results show that within ±15 mm of the focus of the lithotripter, the accuracy was better than 4 mm in the lateral directions and 2 mm in the axial direction. Using off-the-shelf hardware, the algorithm can calculate stone positions every 1 s allowing for real-time tracking during lithotripsy.

Routine Antibiotic Prophylaxis Is Not Required for Patients Undergoing Shockwave Lithotripsy: Outcomes from a National Shockwave Lithotripsy Database in New Zealand.

PURPOSE: To assess the effectiveness of routine prophylactic antibiotics in the prevention of urinary tract infection (UTI) after extracorporeal shockwave lithotripsy (SWL) and identify predictors of UTI development in a multicenter series of over 10,000 stone cases treated in New Zealand over a 20-year period. MATERIALS AND METHODS: Patients treated with SWL on the Mobile Medical Technology vehicle between June 19, 1995 and December 1, 2014 were identified. Data collection was undertaken prospectively for patient, stone and treatment characteristics, and, retrospectively, for treatment outcomes. The primary outcome was clinical UTI, defined as development of UTI symptoms requiring antibiotic therapy. Secondary outcomes included urinary sepsis, need for hospital admission due to infectious complications, and length of hospital stay. Multivariate analysis was undertaken to identify factors independently associated with the development of post-SWL UTI. RESULTS: Antibiotic prophylaxis was used in 62.1% (n = 6710) of cases. On comparing patients who received prophylactic antibiotics to those in whom antibiotics were withheld, no significant differences were observed in terms of post-SWL UTI (1.1% vs 1.3%, p = 0.335) or urinary sepsis (0.04% vs 0.15%, p = 0.075). The use of prophylactic antibiotics was not independently associated with post-SWL UTI (OR: 1.269, 95% CI: 0.886-1.818, p = 0.194). Female gender, larger stone size, and higher number of delivered shocks were predictive of UTI development, but antibiotic prophylaxis did not appear to offer any benefit in this subgroup. CONCLUSIONS: Routine antibiotic prophylaxis was not associated with a reduction in clinical UTI after SWL in this cohort of over 10,000 stone cases in New Zealand.

Proteomic changes in response to crystal formation in Drosophila Malpighian tubules.

Kidney stone disease is a major health burden with a complex and poorly understood pathophysiology. Drosophila Malpighian tubules have been shown to resemble human renal tubules in their physiological function. Herein, we have used Drosophila as a model to study the proteomic response to crystal formation induced by dietary manipulation in Malpighian tubules. Wild-type male flies were reared in parallel groups on standard medium supplemented with lithogenic agents: control, Sodium Oxalate (NaOx) and Ethylene Glycol (EG). Malpighian tubules were dissected after 2 weeks to visualize crystals with polarized light microscopy. The parallel group was dissected for protein extraction. A new method of Gel Assisted Sample Preparation (GASP) was used for protein extraction. Differentially abundant proteins (p<0.05) were identified by label-free quantitative proteomic analysis in flies fed with NaOx and EG diet compared with control. Their molecular functions were further screened for transmembrane ion transporter, calcium or zinc ion binder. Among these, 11 candidate proteins were shortlisted in NaOx diet and 16 proteins in EG diet. We concluded that GASP is a proteomic sample preparation method that can be applied to individual Drosophila Malpighian tubules. Our results may further increase the understanding of the pathophysiology of human kidney stone disease.

Trends in urological stone disease: a 5-year update of hospital episode statistics.

OBJECTIVE: To provide a 5-year follow-on update on the changes in prevalence and treatment of upper urinary tract (UUT) stone disease in England. METHODS: Data from the Hospital Episode Statistics (HES) website (http://www.hesonline.nhs.uk) were extracted, summarised, analysed, and presented. RESULTS: The total number of UUT stone hospital episodes increased slightly from 83 050 in 2009-2010 to 86 742 in 2014-2015 (4.4% increase). The use of shockwave lithotripsy (SWL) for treating all UUT stones remained stable over the 5-year study period following a significant increase in previous years. There was a 49.6% increase in the number of ureteroscopic stone treatments from 12 062 in 2009-2010 to 18 055 in 2014-2015. Increase in ureterorenoscopy (flexible ureteroscopy) showed the most rapid increase from 3 267 to 6 631 cases in the 5-year study period (103% increase). The gap between the total number of ureteroscopies and SWL treatments continues to narrow. Open stone surgery continued to decline with only 30 reported cases in 2014-2015. Due to the continued rapid increase in the number of ureteroscopies performed, treatment for stone disease has continued to increase significantly in comparison to other urological activity. CONCLUSION: This study provides an update on the changing landscape of the management of UUT stones in England. It shows a sustained high prevalence of stone disease commensurate with levels in other developed countries. This study reveals a trend in the last 5 years to surgically intervene on a higher proportion of patients with stones. As in other countries, there is a significant increase in the use of ureteroscopy (particularly intrarenal flexible ureteroscopy) in England. These data have important implications for work-force planning, training, service delivery, and research in the field of urolithiasis.

Shock wave lithotripsy (SWL): outcomes from a national SWL database in New Zealand.

OBJECTIVES: To present the national outcomes for New Zealand of over 9000 stone cases treated with SWL at 21 centres over a 20 year period. SUBJECTS/PATIENTS AND METHODS: Stone cases treated with SWL on board the Mobile Medical Technology (MMT) vehicle between 19 June 1995 and 1 December 2014 were identified, and data collection undertaken prospectively for patient, stone and treatment characteristics, and retrospectively for treatment outcomes. The primary outcome was treatment success, defined as complete stone clearance or clinically insignificant residual fragments (CIRFs) of ≤4 mm. Secondary outcomes were stone free rate, complications and auxiliary procedures, and all statistical analyses were descriptive. RESULTS: 9538 stone cases (7769 patients) were included. The overall, cumulative success rate was 58.7%; this included 45.1% that were stone free and 13.5% in which there were CIRFs ≤4 mm. Success rates varied widely by stone size and location. Overall rates of urinary tract infection, perinephric haematoma, hospital admission and ureteral stent placement were 1.1%, 0.2%, 6.8% and 4.1%, respectively. Variations in SWL protocols across centres limits the overall reliability of our findings. CONCLUSION: SWL remains a low morbidity management option requiring careful patient selection. This study provides valuable data for patient counseling and the formation of evidence based guidelines in SWL. The MMT SWL service has demonstrated that is it possible to deliver a high volume specialist stone service without requiring patients to travel further for treatment.

In Vitro Assessment of Three Clinical Lithotripters Employing Different Shock Wave Generators.

OBJECTIVE: To test the hypothesis that shock wave lithotripsy machines vary in their ability to fragment standardized artificial urinary calculi. MATERIALS AND METHODS: An in vitro test configuration was used to fragment synthetic U-30 Gypsum (U.S. Gypsum, Chicago, IL) stones (mean length 7.1 ± 0.2 mm, mean diameter 6.5 ± 0.07 mm, mean mass 299 ± 16 mg) using the Sonolith i-sys (EDAP TMS, Vaulx-en-Velin, France), Modulith SLX F2 (Storz Medical AG, Tägerwilen, Switzerland), and Piezolith 3000 (Richard Wolf GmbH, Knittlingen, Germany) lithotripters. Gypsum stones were placed at the nominal focus and treated with 250, 500, or 1000 shocks. The residual mass following passage through a 2-mm wire mesh was measured and compared using ANOVA and the Tukey-Kramer HSD test. RESULTS: There was no statistically significant difference between the Modulith SLX F2 and Piezolith 3000 lithotripters for 250 and 1000 shock treatments (p = 0.34 and 0.31, respectively). The Piezolith 3000 demonstrated the most favorable stone mass reduction for 500 shock treatments (187.4 ± 45.2 mg). The Sonolith i-sys was found to be significantly less effective than the other lithotripters for all shockwave conditions. Furthermore, performance of the Sonolith i-sys decreased beyond a threshold generator electrode age of 6000 shocks. CONCLUSIONS: This in vitro study found considerable variability in the ability of lithotripters to fragment synthetic urinary calculi. Synthetic stones were employed to provide a repeatable means of assessing variability in fragmentation efficiency of lithotripters. The Modulith SLX F2 and Piezolith 3000 are broadly equal and resulted in greater fragmentation efficiencies than the Sonolith i-sys. The performance of the Sonolith i-sys deteriorates at 6000 shocks, before the specified lifetime of 20,000 shocks.