Factors determining stone-free rate in shock wave lithotripsy using standard focus of Storz Modulith SLX-F2 lithotripter

Factors related to the success rate of pediatric extracorporeal shock wave lithotripsy (ESWL) in Cipto Mangunkusumo Hospital: an 8-year single-center experience

Background

ESWL is still considered as the first favorable therapeutic option for urinary stone disease with acceptable effectivity. However, factors associated with favorable outcome have not been widely studied in pediatrics due to the small number of urinary stone prevalence. The aim of this study is to evaluate the factors associated with the success rate of pediatric ESWL in our center according to immediate stone-free rate and 3-month stone-free rates.

Methods

This is a retrospective cohort study of children less than 18 years who had ESWL for urolithiasis from January 2008 until August 2015. Patient’s characteristics including age, gender, BMI, stone location, stone length, stone burden, stone opacity, and number of ESWL sessions were gathered from the medical record. Nutritional status was determined according to the Centers for Disease Control and Prevention BMI curve. The outcome of this study was the factors related to the success rate in pediatric ESWL.

Results

Extracorporeal shock wave lithotripsy was done for 36 patients and 39 renal units (RUs) with mean age of 13.7 ± 4.3 years old, height of 1480 ± 16.0 cm, and BMI of 20.0 ± 3. Of 36 patients included, 39 renoureteral units (RUs) and 46 ESWL sessions were recorded. The mean overall treatment was 1.2 ± 0.5 sessions with mean stone length of 11.1 ± 6.3 mm and stone burden of 116.6 ± 130.3 mm2. Within 3 months of follow-up, we recorded that the overall 3-month success rate was 100%, while the overall 3-month stone-free rate was 66.7%. Stone length (p < 0.001 and p < 0.001), stone perpendicular length (p < 0.001 and p < 0.001), and stone burden (p < 0.001 and p = 0.001) were found to be significantly associated with immediate success and 3-month stone-free status, respectively.

Conclusions

ESWL is an effective and safe modality to treat pediatric urolithiasis cases. Stone length, stone perpendicular length, and stone burden were found to be associated with immediate success and 3-month stone-free status after pediatric ESWL treatment.

Is extracorporeal shockwave lithotripsy (SWL) still suitable for >1.5 cm intrarenal stones? Data analysis of 1902 SWLs

PURPOSE

According to the American Urological Association and European Association of Urology guidelines, shockwave lithotripsy (SWL) is the least-invasive treatment option for kidney stones smaller than 2 cm. However, it is well known that SWL stone-free rates (SFR) decline as stone size increases. We sought to evaluate whether the size limit of 1.5 cm could be a better predictor of success after a single SWL session than current recommendations.

METHODS

Data from an SWL-dedicated center were prospectively scrutinized according to stone locations and sizes. Information on patients' demography, lithotripsy parameters, and outcomes was evaluated by multivariate analysis among 1902 SWLs.

RESULTS

The overall SFR was 70.8% (1347/1902). SFRs according to stone size were <1 cm: 73.8% (825/1118), 1-1.5 cm: 70.4% (401/569) and >1.5 cm: 56.2% (121/215); and according to calculi location were lower pole (LP) 64.4% (398/618), mid pole 73.8% (339/459), upper pole 73.8% (273/370) and renal pelvis 74.1% (337/455). Multivariate analysis revealed better SFR independent better SFR in <1.5 cm (p < 0.01), and non-LP stones (p < 0.01).

CONCLUSION

SWL is an effective treatment modality for kidney stones. The single session reached up to 74.8% SFRs (range 70.8%-74.8%) when indicated for intrarenal non LP stones smaller than 1.5 cm. Patients with stones >1.5 cm or >1 cm located in the LP should be counseled on the lower SFRs after a single SWL session.

Prediction of stone-free rates following extracorporeal shockwave lithotripsy in a contemporary cohort of patients with stone densities exceeding 1000 HU

Purpose: Nephrolithiasis is a common urologic problem, and its incidence is increasing. Shockwave Lithotripsy (SWL) has better results for patients with stones < 1000 HU. We attempted to identify SWL stone-free (SF) predictors for > 1000 HU stones.Methods: From January 2013 to September 2019, patient shared decision consecutive SWL for the treatment of a single > 1000 HU renal stone diagnosed by non-contrast computed tomography (NCCT). Endpoints: Fragmentation and SF or clinically insignificant residual fragments ≤ 4 mm at 4 weeks. Age, gender, stone side, location, size and density, number and average energy (Joules) of shocks were explored on uni- and multivariate regression analysis.Results: All sixty-one patients included were diagnosed with renal stone between 5 and 20 mm (maximum length) and underwent one SWL session only: 62.3% males, median age 48 (21-80) years, mean stone size 9.43 ± 2.9 mm (6.0-20.0), mean density 1210 ± 135 HU (1000-1558). There were 39 (63.9%) cases of SF, 16 (26.2%) of partial success and six (9.8%) of no success. Stone size was the only independent predictor of fragmentation, OR = 1.83, 95% CI = 1.32-2.55, p = 0.0003, and SF OR = 1.91, 95% CI = 1.31-2.78, p = 0.008. The best discriminatory stone size on ROC analysis was 1 cm.Conclusion: Stone size was the only significant success predictor in our cohort, with 76% SF rate for stones < 1 cm in 4 weeks follow-up, supporting that renal stones > 1000 HU may be suitable to SWL.

How can and should we optimize extracorporeal shockwave lithotripsy?

It is well recognized that the popularity of extracorporeal shock wave lithotripsy (SWL), despite its non-invasive character, has decreased during recent years. This is partly explained by the technological achievements in endoscopy and urologists’ enthusiasm for such procedures. Another explanation is that many urologists have been insufficiently successful with SWL. The latter effect might to some extent be a result of the performance of the lithotripter used, but in too many cases, it is evident that the principles of how shock wave lithotripsy should be carried out are poorly applied. The purpose of this article is to emphasize some important aspects on how SWL best should be used. Based on decades of experience, it stands to reason that success with SWL does not come automatically and attention has to be paid to all details of this technique.

Comparison of escalating, constant, and reduction energy output in ESWL for renal stones: multi-arm prospective randomized study

This study was designed to find out the optimized energy delivery strategy in Shock Wave Lithotripsy (SWL) that yield to the best stone-free rate (SFR). In this clinical trial, 150 consecutive patients were randomized into three groups: (a) Dose escalation, 1500 SW at 18 kV, followed by 1500 SW at 20 kV then 1500 SW at 22 kV. (b) Constant dose, 4500 SW at 20 kV. All patients undergo plain X-ray film of the urinary tract at day 1, 14, and 90 to assess stone-free rate (SFR) which was defined as no stones or painless fragments less than 4 mm. (c) Dose reduction, 1500 SW at 22 kV, followed by 1500 SW at 20 kV and then 1500 SW at 18 kV. The three treatment groups were comparable in terms of age, sex, stone size and distribution of the kidneys, and the need for Double J stent use. On day 90, the SFR achieved was 82, 90, and 84 % in the escalating, constant, and reduction energy groups, respectively. However, this rate was not statistically significant (x ² = 1.38, p level = 0.28). At a slow rate of 60 shocks, there was no difference in stone-free rate between different voltages at 1, 14, and 90 days. Our randomized clinical trial showed no statistically significant difference in SFR between the three groups while using the slow SWL rate. Our trial is the first randomized trial comparing the three strategies. As such, a dose adjustment strategy while delivering SWL in slow rate was not recommended.

Has the pelvic renal stone position inside the upper loop of JJ stent any influence on the extracorporeal shock wave lithotripsy results?

Background

JJ stents are often encountered in patients with pelvic renal stones referred for shock wave lithotripsy, most of them being placed either for obstructive renal pelvic stones or for ureteric stones mobilized retrograde during the JJ stent insertion. The aim of the study was to determine whether the relative stone position in the upper loop of the JJ stent during extracorporeal shock wave lithotripsy (SWL) influences the efficiency of the procedure. The study was designed as a prospective cohort study on 162 patients addressing the same urological department, with single renal pelvic stone (primary or mobilized to the renal pelvis during the insertion of JJ stent), smaller than 15 mm, with JJ stent, treated by SWL using a second generation spark gap lithotripter, 18 kV, 3000 waves/session. Patients were divided in three groups according to the relative position of the stone to the upper loop of the JJ stent as appears on plain X-ray: stone-inside-loop, loop-crossing-stone and stone-outside the loop. The SWL success rate was the primary outcome of the study. p Value, Chi square and Kruskal–Wallis tests were used for statistical analysis.

Results

For stone-inside-loop cases, SWL efficiency was 22.7 versus 42 % for all the other cases (p = 0.002). Other factors for decreased SWL success rate were: higher stone radio-opacity, larger JJ of stent and obese patients. Study limitation is represented by the relative small study group and by the evaluation of stone density using plain X-ray instead of computer tomography.

Conclusions

For pelvic renal stones having the same density characteristics studied by plain X-ray, the SWL efficiency is lower in stone-inside-loop cases comparing with the other positions. The overall stone free rate for renal pelvic stones could be explained by the second generation lithotripter used for all procedures.

Shockwave Lithotripsy Practice Pattern Variations Among and Between American and Canadian Urologists: In Support of Guidelines

PURPOSE

Shockwave lithotripsy (SWL) is a widely utilized form of treatment for urolithiasis. There are new evidence-based recommendations regarding pre-SWL patient work-up and the performance of SWL. The purpose of this study is to determine practice patterns for SWL and to determine if regional variation exists between Canada and the United States.

MATERIALS AND METHODS

A 19-question survey was prepared. Canadian urologists were surveyed through e-mail correspondence. In the United States, members of the Endourologic Society and members of two large stone management groups were surveyed. Canadian and American results were compared using the chi-square and Fisher's exact tests.

RESULTS

Ninety-four Canadian urologists and 187 U.S. urologists completed the survey. Practice patterns differed between countries. Intravenous sedation was more commonly used in Canada (Canada 94.7% vs United States 17.9%, p < 0.001); routine antibiotics were more commonly given in United States (Canada 2.1% vs United States 78.1%, p < 0.001); a shock rate of 2 Hz was more common in Canada (Canada 76.6% vs United States 16.2%, p < 0.00001); rate of discontinuing ASA for renal and ureteral stone treatment was higher in the United States (renal Canada 88.3% vs United States 95.7%, p < 0.02; ureteral Canada 62.4% vs 90.3%, p < 0.0001); and ureteral stents were more commonly used if treating a large stone or patients with solitary kidneys in the United States (large stones Canada 58.2% vs United States 88.8%, p = 0.0001; solitary kidney Canada 50.6% vs 66.3%, p = 0.02).

CONCLUSIONS

This study highlights the absence of standardization of SWL. Significant regional differences exist in practice patterns and performance of SWL between Canadian and American urologists.

Changes in Urolithiasis Referral Patterns for Shock Wave Lithotripsy over a Decade: Was There Adherence to AUA/EAU Guidelines?

OBJECTIVE

The primary objective was to assess changes in referral patterns of urolithiasis for shock wave lithotripsy (SWL) over a decade. The secondary objective was to evaluate the effect of the number of years of practice of referring physicians on these referral patterns.

METHODS

A retrospective review of SWL database was performed for consecutive referrals for SWL at a tertiary stone center between December 1999 and December 2013. Patient demographics and stone characteristics were assessed. The stone location at the time of referral was used as the reference. Retreatments were excluded. In addition, years of practice of the referring physicians were calculated. The 2007 AUA/EAU guidelines on urolithiasis were considered as a reference.

RESULTS

A total of 8,992 SWL treatments were included. After December 2007, there was a significant increase in the percentage of renal pelvic stones referred for SWL (23.0 vs. 27.1%, p < 0.001). Conversely, proximal ureteral stones significantly decreased after 2007 (24 vs. 18.2%, p < 0.001) including stones > 10 mm (5.1 vs. 2.9%, p < 0.001). Otherwise, there were no changes in the referral patterns for SWL of other stone locations before and after December 2007 (p > 0.05). Furthermore, percentage of stones referred for SWL by urologists practicing for less than 10 years significantly decreased after December 2007 (29.5 vs. 22.8%, p < 0.001).

CONCLUSIONS

The significant reduction in the referral of proximal ureteral stones after December 2007 corresponds to the latest AUA/EAU guidelines on management of ureteral stones.

Evaluation of renal function in patients with a main renal stone larger than 1 cm and perioperative renal functional change in minimally invasive renal stone surgery: a prospective, observational study

PURPOSE

To compare the perioperative relative renal function and determine predictors of deterioration and recovery of separate renal function in patients with renal stones >10 mm and who underwent mini-percutaneous nephrolithotomy or retrograde intra-renal surgery.

PATIENTS AND METHODS

A main stone >10 mm or stones growing, high-risk stone formers and extracorporeal shock-wave lithotripsy-resistant stones were prospectively included in 148 patients. Patients with bilateral renal stones and anatomical deformities were excluded. Renal function was evaluated by estimated glomerular filtration rate, 99m-technetium dimercaptosuccinic acid and 99m-technetium diethylenetriamine pentaacetate prior to intervention and at postoperative 3 months. Logistic regression analyses were performed to find predictors of functional deterioration and recovery.

RESULTS

The overall stone-free rate was 85.1 %. A third of patients (53/148, 35.8 %) with renal stones >10 mm showed deterioration of separate renal function. Mean renal function of operative sites showed 58.2 % (36.8 %/63.2 %) of that of contralateral sites in these patients. Abnormal separate renal function showed postoperative recovery in 31 patients (58.5 %). Three cases (5.7 %) showed deterioration of separate renal function despite no presence of remnant stones. Improvement rates of the abnormal separate renal function did not differ according to the type of surgery. The presence of hydronephrosis and three or more stones were significant predictors for renal function deterioration. Female gender and three or more stones were significantly correlated with postoperative recovery.

CONCLUSIONS

Mini-percutaneous nephrolithotomy or retrograde intra-renal surgery was effective and safe for renal function preservation. Patients with multiple large stones should be considered for candidates of active surgical removal.

Shock wave lithotripsy: the new phoenix?

INTRODUCTION

Following its introduction in 1980, shock wave lithotripsy (SWL) rapidly emerged as the first-line treatment for the majority of patients with urolithiasis. Millions of SWL therapies have since been performed worldwide, and nowadays, SWL still remains to be the least invasive therapy modality for urinary stones. During the last three decades, SWL technology has advanced in terms of shock wave generation, focusing, patient coupling and stone localization. The implementation of multifunctional lithotripters has made SWL available to urology departments worldwide. Indications for SWL have evolved as well. Although endoscopic treatment techniques have improved significantly and seem to take the lead in stone therapy in the western countries due to high stone-free rates, SWL continues to be considered as the first-line therapy for the treatment of most intra-renal stones and many ureteral stones.

METHODS

This paper reviews the fundamentals of SWL physics to facilitate a better understanding about how a lithotripter works and should be best utilized.

RESULTS

Advances in lithotripsy technology such as shock wave generation and focusing, advances in stone localization (imaging), different energy source concepts and coupling modalities are presented. Furthermore adjuncts to improve the efficacy of SWL including different treatment strategies are reviewed.

CONCLUSION

If urologists make use of a more comprehensive understanding of the pathophysiology and physics of shock waves, much better results could be achieved in the future. This may lead to a renaissance and encourage SWL as first-line therapy for urolithiasis in times of rapid progress in endoscopic treatment modalities.

Comparison of shock wave lithotripsy, flexible ureterorenoscopy and percutaneous nephrolithotripsy on moderate size renal pelvis stones

To compare success and complication rates of shock wave lithotripsy (SWL), flexible ureterorenoscopy (F-URS) and percutaneous nephrolithotripsy (PNL) according to modified clavien grading system of renal pelvis stones between 1 and 2 cm. The results of 149 patients were evaluated retrospectively. Patients were divided into three groups as 52 for SWL, 47 for F-URS and 50 for PNL. Complications were evaluated by modified Clavien grading system. In the first group, stone-free rates after a mean of 2, 6 sessions was 86 % (45/52). In Group 2, this ratio was 91.4 % (43/47), and in Group 3, it was 98 % (49/50). The success rate in Group 3 was significantly higher than other groups. Complication rates for Group 1, 2 and 3 were 7.6 % (4/52), 6.3 % (3/47) and 12 % (6/50), respectively. Although PNL was the most successful technique compared with other techniques, complications were also higher in this group. Even though PNL is the most successful, it should be performed for selected patient groups and indications should be carefully evaluated.

Body mass index and buttock circumference are independent predictors of disintegration failure in extracorporeal shock wave lithotripsy for ureteral calculi

BACKGROUND/PURPOSE

Effective stone disintegration by extracorporeal shockwave lithotripsy (ESWL) may depend on patient- and stone-related factors. We investigated predictors of disintegration failure in ESWL for a solitary ureteral calculus.

METHODS

From July 2008 to May 2010, 203 patients who underwent ESWL for a solitary ureteral calculus were enrolled. Clinical and radiologic data were collected, and factors related to ESWL failure were analyzed.

RESULTS

Fifty-two patients (25.6%) showed ESWL failure, with a mean follow-up of 41 days. Forty patients (19.7%) required retreatment, including 12 who underwent repeat ESWL and 28 who underwent curative ureteroscopy. Patients with ESWL failure had significantly higher body weight, body mass index (BMI), and buttock circumference (BC) than patients for whom ESWL was successful. Univariate analysis showed that stone burden (odds ratio [OR], 1.04; 95% confidence interval [CI], 1.03-1.06) and BC (OR, 1.06; 95% CI, 1.01-1.11) were predictors of ESWL failure, while BMI was a potential predictor with borderline significance (OR, 1.09; 95% CI, 0.99-1.20). Multivariate analysis showed that stone burden (OR, 1.04; 95% CI, 1.03-1.06) was a significant predictor for all patients. On stratifying patients according to the level of ureteral calculi, BC was found to be an independent predictor (OR, 1.35; 95% CI, 1.02-1.80) for ESWL failure for middle/lower ureteral calculi and BMI (OR, 1.47; 95% CI, 1.13-1.91) for upper ureteral calculi.

CONCLUSION

Stone burden is the main predictor of ESWL failure for all patients with ureteral calculi. BC and BMI are independent predictors for ESWL failure for middle/lower and upper ureteral calculi, respectively.

Comparison of shockwave lithotripsy and microperc for treatment of kidney stones in children

PURPOSE

We aimed to compare the outcomes of microperc and shockwave lithotripsy (SWL) for treatment of kidney stones in children.

PATIENTS AND METHODS

The medical records of 145 patients under the age of 15 years with opaque and single kidney stones treated with either SWL or microperc were retrospectively reviewed. Both groups were compared in terms of fluoroscopy and operative time, re-treatment, complications, success rate, and secondary and total number of procedures.

RESULTS

Microperc and SWL were performed on 37 and 108 pediatric patients, respectively. The mean age of the patients was 5.91±4.03 years (1-15) and 8.43±4.84 (1-15) years in the SWL and microperc groups, respectively (P=0.004). The mean stone size was 11.32±2.84 (5-20) mm in the SWL group and 14.78±5.39 (6-32) mm in the microperc group (P<0.001). In the SWL group, 31 (28.7%) patients underwent a second SWL session and 6 (5%) had a third session. Finally, 95 (88%) patients were stone free at the end of the SWL sessions. In the microperc group, the stone-free rate was 89.2% in a single session (P=0.645). The mean duration of hospitalization was 49.2±12.3 (16-64) hours in the microperc group and 8.4±2.3 (6-10) hours per one session in the SWL group (P<0.001). The fluoroscopy time was significantly longer in the microperc group compared with the SWL group (147.3±95.3 seconds vs 59.6±25.9 seconds, P<0.001). The rate of requirement for an auxiliary procedure was higher in the SWL group than in the microperc group. The overall complication rates for the microperc and SWL groups were 21.6% and 16.7%, respectively (P=0.498).

CONCLUSIONS

The results of our study demonstrate that microperc provides a similar stone-free rate and a lower additional treatment rate compared with SWL in the treatment of kidney stone disease in children.

The feasibility of shockwave lithotripsy for treating solitary, lower calyceal stones over 1 cm in size

INTRODUCTION

Recently, few studies were reported about the treatment of large, solitary, renal calculi between shockwave lithotripsy (SWL) and percutaneous nephrolithotomy (PNL). We assess the feasibility of SWL for managing solitary, lower calyceal stones over 1 cm by comparing the results of lower pole calculi treatment between patients that underwent SWL or PNL.

METHODS

We retrospectively reviewed clinical data for patients who had undergone PNL or SWL due to lower calyceal stones over 1 cm. Group 1 consisted of patients who underwent SWL to treat lower pole renal calculi from 2010 to 2011. Group 2 included patients who underwent PNL to manage lower pole renal calculi from 2008 to 2009. We compared patient age, gender, stone size, comorbidities, postoperative complications, additional interventions and anatomical parameters between the two groups.

RESULTS

A total of 55 patients were enrolled in this study. The mean ages (±SD) of groups 1 (n = 33) and 2 (n = 22) were 55.1 (±13.0) and 50.0 (±10.6) years (p = 0.133) and mean stone sizes were 1.6 (±0.7) and 1.9 (±0.8) cm (p = 0.135), respectively. There were no significant differences in gender distribution, comorbidities or stone laterality between the two groups. No significant differences in various parameters were observed between patients with stones 1 to 2 cm and ones with stones 2 cm or larger.

CONCLUSIONS

Our results demonstrated that SWL is a safe, feasible treatment for solitary, lower calyceal stones over 1 cm.

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.

Evaluation of shock wave lithotripsy injury in the pig using a narrow focal zone lithotriptor

What's known on the subject? and What does the study add? Of all the SW lithotriptors manufactured to date, more research studies have been conducted on and more is known about the injury (both description of injury and how to manipulate injury size) produced by the Dornier HM-3 than any other machine. From this information have come suggestions for treatment protocols to reduce shock wave (SW)-induced injury for use in stone clinics. By contrast, much less is known about the injury produced by narrow-focus and high-pressure lithotriptors like the Storz Modulith SLX. In fact, a careful study looking at the morphology of the injury produced by the SLX itself is lacking, as is any study exploring ways to reduce renal injury by manipulating SW delivery variables of this lithotriptor. The present study quantitates the lesion size and describes the morphology of the injury produced by the SLX. In addition, we report that reducing the SW delivery rate, a manoeuvre known to lower injury in the HM-3, does not reduce lesion size in the SLX.

OBJECTIVE

• To assess renal injury in a pig model after treatment with a clinical dose of shock waves using a narrow focal zone (≈3 mm) lithotriptor (Modulith SLX, Karl Storz Lithotripsy).

MATERIALS AND METHODS

• The left kidney of anaesthetized female pigs were treated with 2000 or 4000 shock waves (SWs) at 120 SWs/min, or 2000 SWs at 60 SWs/min using the Storz SLX. • Measures of renal function (glomerular filtration rate and renal plasma flow) were collected before and 1 h after shock wave lithotripsy (SWL) and the kidneys were harvested for histological analysis and morphometric quantitation of haemorrhage in the renal parenchyma with lesion size expressed as a percentage of functional renal volume (FRV). • A fibre-optic probe hydrophone was used to determine acoustic output and map the focal width of the lithotriptor. • Data for the SLX were compared with data from a previously published study in which pigs of the same age (7-8 weeks) were treated (2000 SWs at 120 or 60 SWs/min) using an unmodified Dornier HM3 lithotriptor.

RESULTS

• Treatment with the SLX produced a highly focused lesion running from cortex to medulla and often spanning the full thickness of the kidney. Unlike the diffuse interstitial haemorrhage observed with the HM3, the SLX lesion bore a blood-filled core of near-complete tissue disruption devoid of histologically recognizable kidney structure. • Despite the intensity of tissue destruction at the core of the lesion, measures of lesion size based on macroscopic determination of haemorrhage in the parenchyma were not significantly different from kidneys treated using the HM3 (2000 SWs, 120 SWs/min: SLX, 1.86 ± 0.52% FRV; HM3, 3.93 ± 1.29% FRV). • Doubling the SW dose of the SLX from 2000 to 4000 SWs did not significantly increase lesion size. In addition, slowing the firing rate of the SLX to 60 SWs/min did not reduce the size of the lesion (2.16 ± 0.96% FRV) compared with treatment at 120 SWs/min, as was the case with the HM3 (0.42 ± 0.23% FRV vs 3.93 ± 1.29% FRV). • Renal function fell significantly below baseline in all treated groups but was similar for both lithotriptors. • Focal width of the SLX (≈2.6 mm) was about one-third that of the HM3 (≈8 mm) while peak pressures were higher (SLX at power level 9: P+≈90 MPa, P-≈-12 MPa; HM3 at 24 kV: P+≈46 MPa, P-≈-8 MPa).

CONCLUSIONS

• The lesion produced by the SLX (narrow focal width, high acoustic pressure) was a more focused, more intense form of tissue damage than occurs with the HM3. • Slowing the SW rate to 60 SWs/min, a strategy shown to be effective in reducing injury with the HM3, was not protective with the SLX. • These findings suggest that the focal width and acoustic output of a lithotriptor affect the renal response to SWL.

A 970 Hounsfield units (HU) threshold of kidney stone density on non-contrast computed tomography (NCCT) improves patients' selection for extracorporeal shockwave lithotripsy (ESWL): evidence from a prospective study

What's known on the subject? and What does the study add? Stone density on non-contrast computed tomography (NCCT) is reported to be a prognosis factor for extracorporeal shockwave lithotripsy (ESWL). In this prospective study, we determined that a 970 HU threshold of stone density is a very specific and sensitive threshold beyond which the likelihood to be rendered stone free is poor. Thus, NCCT evaluation of stone density before ESWL may useful to identify which patients should be offered alternative treatment to optimise their outcome.

OBJECTIVE

• To evaluate the usefulness of measuring urinary calculi attenuation values by non-contrast computed tomography (NCCT) for predicting the outcome of treatment by extracorporeal shockwave lithotripsy (ESWL).

PATIENTS AND METHODS

• We prospectively evaluated 50 patients with urinary calculi of 5-22 mm undergoing ESWL. • All patients had NCCT at 120 kV and 100 mA on a spiral CT scanner. Patient age, sex, body mass index, stone laterality, stone size, stone attenuation values (Hounsfield units [HU]), stone location, and presence of JJ stent were studied as potential predictors. • The outcome was evaluated 4 weeks after the ESWL session by NCCT. • ESWL success was defined as patients being stone-free (SF) or with remaining stone fragments of <4 mm, which were considered as clinically insignificant residual fragments (CIRF).

RESULTS

• Our survey concluded that 26 patients (52%) were SF, 12 (24%) had CIRF and 12 (24%) had residual fragment on NCCT after a one ESWL treatment. • Stones of patients who became SF or had CIRF had a lower density compared with stones in patients with residual fragments [mean (sd) 715 (260) vs 1196 (171) HU, P < 0.001]. • The Youden Index showed that a stone density of 970 HU represented the most sensitive (100%) and specific (81%) point on the receiver-operating characteristic curve. • The stone-free rate for stones of <970 HU was 96% vs 38% for stones of ≥ 970 HU (P < 0.001). A linear relationship between the calculus density and the success rate of ESWL was identified.

CONCLUSION

• The use of NCCT to determine the attenuation values of urinary calculi before ESWL helps to predict treatment outcome, and, consequently, could be helpful in planning alternative treatment for patients with a likelihood of a poor outcome from ESWL.

Impact of radiological technologists on the outcome of shock wave lithotripsy

OBJECTIVE

To evaluate the correlation of radiological technologists (RTs) and the outcome of shock wave lithotripsy (SWL) in terms of fluoroscopy time, fragmentation rate, and stone-free rate.

MATERIAL AND METHODS

A retrospective review of a prospectively collected database of 601 SWL treatments between June 2009 and March 2010 was performed. Patients with radiolucent stones were excluded. SWL was done by 6 RTs with different levels of experience. Follow up was available for 534 treatments. Multivariate analysis was performed.

RESULTS

RTs (A-F) performed 144, 109, 118, 58, 57, and 48 SWL sessions, respectively. There was no statistical difference among RTs in terms of mean stone size or stone location. Compared with other RTs, RT A had a significantly lower mean fluoroscopy time of 129 seconds (95% CI 120.8-137.3) (P <.001), higher stone-free rate (75.7%; P = .035), and stone fragmentation rate after a single SWL session (82.6%; P = .004). After correcting for stone size and location, fluoroscopy time (P <.001), fragmentation rate (P = .002), and stone-free rate (P = .04) maintained their significance. When comparing the top 3 RTs performing >100 SWL sessions, RTs B and C had significantly higher fluoroscopy time compared with RT A (OR [95% CI] 1.84 [1.38-2.45]; P <.001 and 2.67 [2.00-3.57]; P <.001), respectively. After correcting for stone size and location, RT B had significantly lower fragmentation rate when compared with RT A (OR [95% CI] 0.21 [0.05-0.86], P = .03]. However, there were no significant differences among the top 3 RTs in terms of stone-free rates.

CONCLUSION

RTs significantly differ in fluoroscopy usage in addition to stone fragmentation and stone-free rates.