Effect of initial shock wave voltage on shock wave lithotripsy-induced lesion size during step-wise voltage ramping

OBJECTIVE

To determine if the starting voltage in a step‐wise ramping protocol for extracorporeal shock wave lithotripsy (SWL) alters the size of the renal lesion caused by the SWs.

MATERIALS AND METHODS

To address this question, one kidney from 19 juvenile pigs (aged 7–8 weeks) was treated in an unmodified Dornier HM‐3 lithotripter (Dornier Medical Systems, Kennesaw, GA, USA) with either 2000 SWs at 24 kV (standard clinical treatment, 120 SWs/min), 100 SWs at 18 kV followed by 2000 SWs at 24 kV or 100 SWs at 24 kV followed by 2000 SWs at 24 kV. The latter protocols included a 3–4 min interval, between the 100 SWs and the 2000 SWs, used to check the targeting of the focal zone. The kidneys were removed at the end of the experiment so that lesion size could be determined by sectioning the entire kidney and quantifying the amount of haemorrhage in each slice. The average parenchymal lesion for each pig was then determined and a group mean was calculated.

RESULTS

Kidneys that received the standard clinical treatment had a mean (sem ) lesion size of 3.93 (1.29)% functional renal volume (FRV). The mean lesion size for the 18 kV ramping group was 0.09 (0.01)% FRV, while lesion size for the 24 kV ramping group was 0.51 (0.14)% FRV. The lesion size for both of these groups was significantly smaller than the lesion size in the standard clinical treatment group.

CONCLUSIONS

The data suggest that initial voltage in a voltage‐ramping protocol does not correlate with renal damage. While voltage ramping does reduce injury when compared with SWL with no voltage ramping, starting at low or high voltage produces lesions of the same approximate size. Our findings also suggest that the interval between the initial shocks and the clinical dose of SWs, in our one‐step ramping protocol, is important for protecting the kidney against injury.     

Pretreatment with low‐energy shock waves induces renal vasoconstriction during standard shock wave lithotripsy (SWL): a treatment protocol known to reduce SWL‐induced renal injury

OBJECTIVE

To test the hypothesis that the pretreatment of the kidney with low‐energy shock waves (SWs) will induce renal vasoconstriction sooner than a standard clinical dose of high‐energy SWs, thus providing a potential mechanism by which the pretreatment SW lithotripsy (SWL) protocol reduces tissue injury.

MATERIALS AND METHODS

Female farm pigs (6‐weeks‐old) were anaesthetized with isoflurane and the lower pole of the right kidney treated with SWs using a conventional electrohydraulic lithotripter (HM3, Dornier GmbH, Germany). Pulsed Doppler ultrasonography was used to measure renal resistive index (RI) in blood vessels as a measure of resistance/impedance to blood flow. RI was recorded from one intralobar artery located in the targeted pole of the kidney, and measurements taken from pigs given sham SW treatment (Group 1; no SWs, four pigs), a standard clinical dose of high‐energy SWs (Group 2; 2000 SWs, 24 kV, 120 SWs/min, seven pigs), low‐energy SW pretreatment followed by high‐energy SWL (Group 3; 500 SWs, 12 kV, 120 SWs/min + 2000 SWs, 24 kV, 120 SWs/min, eight pigs) and low‐energy SW pretreatment alone (Group 4; 500 SWs, 12 kV, 120 SWs/min, six pigs).

RESULTS

Baseline RI (≈0.61) was similar for all groups. Pigs receiving sham SW treatment (Group 1) had no significant change in RI. A standard clinical dose of high‐energy SWs (Group 2) did not significantly alter RI during treatment, but did increase RI at 45 min after SWL. Low‐energy SWs did not alter RI in Group 3 pigs, but subsequent treatment with a standard clinical dose of high‐energy SWs resulted in a significantly earlier (at 1000 SWs) and greater (two‐fold) rise in RI than that in Group 2 pigs. This rise in RI during the low/high‐energy SWL protocol was not due to a delayed vasoconstrictor response of pretreatment, as low‐energy SW treatment alone (Group 4) did not increase RI until 65 min after SWL.

CONCLUSIONS

The pretreatment protocol induces renal vasoconstriction during the period of SW application whereas the standard protocol shows vasoconstriction occurring after SWL. Thus, the earlier and greater rise in RI during the pretreatment protocol may be causally associated with a reduction in tissue injury.     

Low‐frequency extracorporeal shock wave lithotripsy improves renal pelvic stone disintegration in a pig model

OBJECTIVE

To compare disintegration rates for renal stones treated by 60 vs 120 shock waves (SW)/min at the same energy settings, using standardized validated artificial stones in a pig model.

MATERIALS AND METHODS

Gypsum artificial stones (13 × 6 mm) were inserted into the renal pelvis on either side of 12 anaesthetized pigs by open surgery. Extracorporeal SW lithotripsy (ESWL) was applied using a new electromagnetic lithotripter (Lithoskop®, Siemens AG Healthcare, Munich, Germany) at 60 and 120 SW/min; 3000 SW were applied to each kidney with the same energy settings. Stone fragments were collected after nephrectomy, passed through calibrated test sieves, and weighed. Fragment size categories were stratified according to the sieve hole size as set by the manufacturer. Fragments of ≤4.75 mm were defined as capable of spontaneous passage. For each pig the number of stone fragments of the respective size categories was counted and weighed. The results were analysed statistically using the Mann–Whitney U‐test.

RESULTS

For fragments of >4.75 mm, the median (range) fragment counts were 0 (0–1) for 60 and 1 (0–3) for 120 SW/min (P = 0.006). For small fragments of 2.0–2.8 mm, the median fragment counts were 15 (4–24) for 60 and 10 (2–25) for 120 SW/min (P = 0.033); for fragments of 1.0–2.0 mm the respective values were 42.5 (9–81) and 21.5 (6–56) (P = 0.004). Of the total stone fragment mass in the 60 and 120 SW/min groups, 4.34% and 31.31% were >4.75 mm. There was complete disintegration yielding fragments capable of spontaneous passage in 10 of 12 renal units at 60 and in three of 12 renal units at 120 SW/min. The mean treatment time was 55.4 min for therapy at 60 and 34.3 min for therapy at 120 SW/min (P = 0.001). One parenchymal haematoma of 15 × 10 mm developed in the 60 SW/min group and another of 20 × 10 mm developed in the 120 SW/min group.

CONCLUSION

ESWL fragmentation with equal energy application yields significantly smaller fragments at 60 than at 120 SW/min. The theoretical stone passage rate could therefore be ≈80% for 60 vs 25% for 120 SW/min ESWL. Renal haematoma formation was comparable in both groups.     

Extracorporeal shock wave lithotripsy in children: equivalent clearance rates to adults is achieved with fewer and lower energy shock waves

OBJECTIVE

To compare the outcome, safety and efficiency of extracorporeal shock wave lithotripsy (ESWL) using an electromagnetic lithotripter for upper urinary tract stones in children and adults.

PATIENTS AND METHODS

We retrospectively reviewed data over a 5‐year period for patients with solitary, renal and upper ureteric stones measuring <2 cm in whom ESWL was the treatment method. Group A consisted of 44 children (mean [sd ] age 5.9 [4.4] years) and group B of 562 adults (mean [sd ] age 40.9 [13.1] years). The number and energy of SWs used was not predetermined and was tailored until adequate fragmentation was achieved. Initial stone reassessment was performed at 48 h and monthly thereafter. The number of SWs, intensity of SWs, stone‐free rate, auxiliary procedure rate, re‐treatment rate, complication rate and effectiveness quotient (EQ) were assessed in each group.

RESULTS

The stone‐free rate with ESWL was 84% in children and 87% in adults (P = 0.78). The EQ was 77% and 75% in children and adults, respectively (P = 0.56). The mean (sd ) number of SWs and energy required per session was 950 (349) and 11.83 (0.48) kV in children and 1262 (454) and 12.36 (0.34) kV in adults (P < 0.001). The re‐treatment, auxiliary procedure and complication rates were similar in both groups.

CONCLUSION

ESWL is as safe and effective in children as in adults for solitary renal and upper ureteric stones that are <2 cm. Children required significantly fewer and lower energy SWs to achieve equivalent results.     

Effect of firing rate on the performance of shock wave lithotriptors

OBJECTIVE

To determine the mechanism that underlies the effect of shock wave (SW) rate on the performance of clinical lithotripters.

MATERIALS AND METHODS

The effect of firing rate on the pressure characteristics of SWs was assessed using a fibre‐optic probe hydrophone (FOPH 500, RP Acoustics, Leutenbach, Germany). Shock waves were fired at slow (5–27 SW/min) and fast (100–120 SW/min) rates using a conventional high‐pressure lithotriptor (DoLi‐50, Dornier MedTech America, Inc., Kennesaw, GA, USA), and a new low‐pressure lithotriptor (XX‐ES, Xi Xin Medical Instruments Co. Ltd, Suzhou, PRC). A digital camcorder (HDR‐HC3, Sony, Japan) was used to record cavitation fields, and an ultrafast multiframe high‐speed camera (Imacon 200, DRS Data & Imaging Systems, Inc., Oakland, NJ, USA) was used to follow the evolution of bubbles throughout the cavitation cycle.

RESULTS

Firing rate had little effect on the leading positive‐pressure phase of the SWs with the DoLi lithotriptor. A slight reduction (≈7%) of peak positive pressure (P+) was detected only in the very dense cavitation fields (≈1000 bubbles/cm³) generated at the fastest firing rate (120 SW/min) in nondegassed water. The negative pressure of the SWs, on the other hand, was dramatically affected by firing rate. At 120 SW/min the peak negative pressure was reduced by ≈84%, the duration and area of the negative pressure component was reduced by ≈80% and ≈98%, respectively, and the energy density of negative pressure was reduced by >99%. Whereas cavitation bubbles proliferated at fast firing rates, HS‐camera images showed the bubbles that persisted between SWs were very small (<10 µm). Similar results were obtained with the XX‐ES lithotriptor but only after recognizing a rate‐dependent charging artefact with that machine.

CONCLUSION

Increasing the firing rate of a lithotriptor can dramatically reduce the negative pressure component of the SWs, while the positive pressure remains virtually unaffected. Cavitation increases as the firing rate is increased but as the bubbles collapse, they break into numerous microbubbles that, because of their very small size, do not pose a barrier to the leading positive pressure of the next SW. These findings begin to explain why stone breakage in SWL becomes less efficient as the firing rate is increased.     

Multimodal evaluation of renal perfusional changes due to extracorporeal shock wave lithotripsy

OBJECTIVES

To examine the effect of extracorporeal shock wave lithotripsy (ESWL) on renal perfusion before and after treatment, by assessing renal resistive index (RI) using colour Doppler ultrasonography (CDUS), magnetic resonance perfusion imaging (MRPI), radionuclide renography and big‐endothelin‐1 values (Big‐ET‐1).

PATIENTS AND METHODS

In 69 normotensive patients the RI was measured before, 1, 3, 6 and 24 h after ESWL using CDUS. The RI values, measured in interlobar/arcuate arteries, were correlated with the findings on MRPI, done before and within 24 h after ESWL. In addition, renal plasma flow (RPF, assessed on radionuclide renography) and Big‐ET‐1 levels (a potent vasoconstrictor peptide), served as a control for evaluating renal perfusion. The patients were stratified in three age groups, i.e. ≤39, 40–59 and ≥60 years, with 23 patients in each group.

RESULTS

The mean (sd ) RI increased significantly in the treated kidneys, from 0.64 (0.05) before to 0.72 (0.08) after ESWL (P = 0.001). Only in patients aged ≥60 years did the RI continue to increase over the 24 h. MRPI showed a decrease of renal blood flow (RBF) in all age groups, but most significantly in those aged ≥60 years. The radionuclide renography and big‐ET‐1 levels changed significantly only in the oldest group. The best correlation was between RI and RBF changes detected by MRPI.

CONCLUSIONS

ESWL obviously causes disturbances of renal perfusion, particularly in elderly patients (≥60 years). Measurement of RI with Doppler techniques might provide useful information for the clinical diagnosis of renal damage.     

Localization of renal oxidative stress and inflammatory response after lithotripsy

OBJECTIVE

To determine if the acute renal oxidative stress and inflammation after extracorporeal shock wave lithotripsy (ESWL), thought to be mediated by ischaemia, is most severe in the portion of the kidney within the focal zone of the lithotripter, and if these effects result primarily from ischaemic injury.

MATERIALS AND METHODS

Pigs (7–8‐weeks old) received either 2000 shock waves at 24 kV to the lower‐pole calyx of one kidney or unilateral renal ischaemia for 1 h. A third group (sham) received no treatment. Timed urine and blood samples were taken for analysis of lipid peroxidation and the inflammatory cytokines, tumour necrosis factor‐α (TNF‐α) and interleukin‐6 (IL‐6). At 4 h after treatment, kidneys were removed and samples of cortex and medulla were frozen for analysis of cytokines and heme oxygenase‐1 (HO‐1).

RESULTS

ESWL did not affect urinary excretion of malondialdehyde, but did elicit an eight‐fold induction of HO‐1 in the portion of the renal medulla within the focal zone of the lithotripter (F2), while remaining unchanged elsewhere in the treated kidney. There was no induction of HO‐1 in renal tissue after ischaemia‐reperfusion. Urinary excretion of TNF‐α increased from the lithotripsy‐treated kidney by 1 h after treatment, but was unaffected by ischaemia‐reperfusion. As with the HO‐1 response after lithotripsy, IL‐6 increased only in the renal medulla at F2. By contrast, ischaemia‐reperfusion increased IL‐6 in all samples from the treated kidney.

CONCLUSION

These findings show that the acute oxidative stress and inflammatory responses to ESWL are localized to the renal medulla at F2. Furthermore, the differing patterns of markers of injury for ESWL and ischaemia‐reperfusion suggest that ischaemia is not the principal cause of the injury response after ESWL.     

Role of computed tomography with no contrast medium enhancement in predicting the outcome of extracorporeal shock wave lithotripsy for urinary calculi

OBJECTIVE: To evaluate the usefulness of urinary calculi attenuation values from non-contrast computed tomography (NCCT) in predicting the outcome of treatment by extracorporeal shock wave lithotripsy (ESWL). PATIENTS AND METHODS: We evaluated 112 patients with solitary renal and upper ureteric calculi of 0.5-2 cm undergoing ESWL. All patients had NCCT at 120 kV and 240 mA on a spiral CT scanner. During each ESWL session 3000 shock waves were given to a maximum of 3.0 kV. A final X-ray of the kidney, ureters and bladder was taken 12 weeks after the last ESWL session. Fragments of < or = 5 mm were regarded as clinically insignificant residual fragments (CIRF). The calculi retrieved were analysed by X-ray diffraction and the results assessed by comparing the mean density (as measured in Hounsfield units, HU) with the number of ESWL sessions and clearance. RESULTS: In all, 82 (76%) patients had complete clearance of stones and 26 (24%) had CIRF. There was a linear relationship between the calculus density and number of ESWL sessions required. Of patients with calculi of < or = 750 HU, 41 (80%) needed three or fewer ESWL sessions and 45 (88%) had complete clearance. Of patients with calculi of > 750 HU, 41 (72%) required three or more ESWL sessions, and 37 (65%) had complete clearance. The best outcome was in patients with calculus diameters of < 1.1 cm and mean densities of < or = 750 HU; 34 (83%) needed three or fewer ESWL sessions, and the clearance rate was 90%. The worst outcome was in patients with calculus densities of > 750 HU and diameters of > 1.1 cm; 23 (77%) needed three or more ESWL sessions and the clearance rate was only 60%. The calculus density was a stronger predictor of outcome than size alone. CONCLUSIONS: The use of NCCT for determining the attenuation values of urinary calculi before ESWL might help to predict the treatment outcome, and so might help in planning alternative treatment in patients with a likelihood of a poor outcome from ESWL.     

Extracorporeal shock wave lithotripsy (ESWL) of a renal calculus in a liver transplant recipient: report of a severe complication--a case report

Introduction

Extracorporeal shock wave lithotripsy (ESWL) has evolved as a standard treatment modality for calculi of the upper urinary tract. Noninvasive ESWL shows rare life-threatening complications. Herein we have reported the case of a liver transplant recipient who developed severe renal hemorrhage after ESWL of a renal calculus. Transfusion of erythrocytes and platelets led to anaphylactic shock with acute renal failure requiring intensive care. The patient fully recovered shortly thereafter and was discharged home with a residual left kidney stone measuring 8 mm.

Case Presentation

A 55-year-old man with a single left kidney underwent ESWL due to symptomatic left nephrolithiasis. He had undergone successful liver transplantation 11 years earlier. At the time of ESWL his liver functions were normal and his serum creatinine level was 1.3 mg/dL. Two weeks before the treatment a double pigtail ureteral stent was inserted because of a symptomatic left hydronephrosis. Serveral hours after ESWL treatment the patient complained of left-sided flank pain. An ultrasound revealed a large subcapsular hematoma of the left kidney, which was confirmed using abdominal computed tomography (CT). With the patient being hemodynamically stable, we opted for conservative management. Despite postinterventional complications, the patient made a fast recovery.

Conclusion

ESWL is a noninvasive, safe, and efficient method to treat renal calculi. Patients who are at risk for hemorrhage should undergo close postinterventional monitoring, including red blood cell count and renal ultrasound.     

Urolithiasis in the horseshoe kidney: a single-centre experience

OBJECTIVE

To report the operative management and subsequent stone‐free rates of patients with urolithiasis in a horseshoe kidney and treated at one centre.

PATIENTS AND METHODS

We retrospectively reviewed all patients presenting to our centre with a horseshoe kidney and urolithiasis over a 15‐year period. The stone burden, surgical management, complications and stone clearance rates were recorded.

RESULTS

In all, 55 patients with urolithiasis in horseshoe kidney were treated. Percutaneous nephrolithotomy (PCNL) was used in 60 renal units in 47 patients. Five patients had extracorporeal shock wave lithotripsy (ESWL), two had flexible ureteroscopy and one had a laparoscopic pyelolithotomy for a stone extending into the isthmus. PCNL was used for large stones (mean digitized surface area = 614.32 mm²) and required one to four stages to achieve an overall stone clearance rate of 88%. Stones were cleared at one sitting in 77% of PCNL procedures, completely cleared in two‐thirds of patients treated by ESWL, and in both who had flexible ureteroscopy and the one treated with laparoscopic pyelolithotomy. Complications were minimal, with 15% minor and 3% major complications in the PCNL group only.

CONCLUSION

Appropriate management of urolithiasis within the horseshoe kidney depends not only on stone burden, but also on stone location, calyceal configuration and malrotation. Stones can be cleared successfully in almost all patients providing that all techniques are available to the operating surgeon.     

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

Study Type – Therapy (case series)
Level of Evidence 4

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 m². 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.     

Reducing shock number dramatically decreases lesion size in a juvenile kidney model

BACKGROUND AND PURPOSE: Adult stone patients are treated with several thousand lithotripter shockwaves (SWs) in order to pulverize a kidney stone. This typical clinical dose assures that the stone will be fractured completely. However, this same dose induces damage to the kidney, especially pediatric-size kidneys. If increasing SW number is known to increase renal injury and functional impairment, will reducing SW number below typical treatment levels significantly decrease kidney damage and hemodynamic changes? MATERIALS AND METHODS: To address this question, one kidney in each of nine juvenile pigs (6-7 weeks old) was treated with 1000 SWs at 24 kV directed at a lower-pole calix with an unmodified HM-3 lithotripter. Parenchymal-lesion size was determined by sectioning the entire kidney and quantitating the amount of hemorrhage in each slice. Renal function was determined before and after SW treatment by inulin clearance, paraaminohippurate (PAH) extraction, and PAH clearance. The resulting morphologic and functional changes were then compared with those of kidneys that had been treated with a typical clinical dose of 2000 SWs (data previously published; J Am Soc Nephrol 2000;11:310). Eleven pigs were utilized as sham-treated controls. RESULTS: Limiting SW number to 1000 significantly reduced the size of the lesion (by 95%) and reduced the degree of functional change (glomerular filtration rate by 38%, PAH extraction by 73%, renal plasma flow by 46%) compared with kidneys receiving 2000 SWs (an adult dose). CONCLUSIONS: These data support the idea that SW number should be reduced to the lowest number that fractures kidney stones in order to minimize renal injury and functional impairment.     

Independent assessment of a wide-focus, low-pressure electromagnetic lithotripter: absence of renal bioeffects in the pig

OBJECTIVE

To assess the renal injury response in a pig model treated with a clinical dose of shock waves (SWs) delivered at a slow rate (27 SW/min) using a novel wide focal zone (18 mm), low acoustic pressure (<20 MPa) electromagnetic lithotripter (Xi Xin‐Eisenmenger, XX‐ES; Xi Xin Medical Instruments Co. Ltd., Suzhou, PRC).

MATERIALS AND METHODS

The left kidneys of anaesthetized female pigs were treated with 1500 SWs from either an unmodified electrohydraulic lithotripter (HM3, Dornier MedTech America, Inc., Kennesaw, GA, USA; 18 kV, 30 SW/min) or the XX‐ES (9.3 kV, 27 SW/min). Measures of renal function (glomerular filtration rate, GFR, and renal plasma flow) were collected before and after SW lithotripsy, and kidneys were harvested for histological quantification of vascular haemorrhage, expressed as a percentage of the functional renal volume (FRV). A fibre‐optic probe hydrophone was used to characterize the acoustic field, and the breakage of gypsum model stones was used to compare the function of the two lithotripters.

RESULTS

Kidneys treated with the XX‐ES showed no significant change in renal haemodynamic function and no detectable tissue injury. Pigs treated with the HM3 had a modest decline from baseline (≈ 20%) in both GFR (P > 0.05) and renal plasma flow (P = 0.064) in the treated kidney, but that was not significantly different from the control group. Although most HM3‐treated pigs showed no evidence of renal tissue injury, two had focal injury measuring 0.1% FRV, localized to the renal papillae. The width of the focal zone for the XX‐ES was ≈ 18 mm and that of the HM3 ≈ 8 mm. Peak positive pressures at settings used to treat pigs and break model stones were considerably lower for the XX‐ES (17 MPa at 9.3 kV) than for the HM3 (37 MPa at 18 kV). The XX‐ES required fewer SWs to break stones to completion than did the HM3, with a mean (sd ) of 634 (42) and 831 (43) SWs, respectively (P < 0.01). However, conditions were different for these tests because of differences in physical configuration of the two machines.

CONCLUSION

The absence of renal injury with the wide focal zone XX‐ES lithotripter operated at low shock pressure and a slow SW rate suggests that this lithotripter would be safe when used at the settings recommended for patient treatment. That the injury was also minimal using the Dornier HM3 lithotripter at a slow SW rate implies that the reduced tissue injury seen with these two machines was because they were operated at a slow SW rate. As recent studies have shown stone breakage to be improved when the focal zone is wider than the stone, a wide focal zone lithotripter operated at low pressure and slow rate has the features necessary to provide better stone breakage with less tissue injury.     

α‐Blockers to assist stone clearance after extracorporeal shock wave lithotripsy: a meta‐analysis

Study Type – Therapy (meta‐analysis)
Level of Evidence 1a

OBJECTIVE

To review the evidence for the use of α‐blockers after extracorporeal shock wave lithotripsy (ESWL) in enhancing the effectiveness of renal and ureteric stone clearance.

METHODS

We searched MEDLINE, Embase and the Cochrane Library up to January 2009. All randomized controlled trials in which α‐blockers were evaluated after ESWL were eligible for the analysis. Outcome measures assessed were clearance rate (primary) and expulsion time (secondary). Two authors independently assessed study quality and extracted data. All data were analysed using RevMan 5.

RESULTS

Of the 29 identified papers, seven trials with a total of 484 patients met the predefined criteria. These studies evaluated the effectiveness of the α‐blocker tamsulosin, and studied clearance rate as the primary outcome. There was large heterogeneity between trials, but their methodological quality was adequate. The pooled absolute risk difference of clearance rate was 16% (95% confidence interval 5–27%) in favour of the tamsulosin group, i.e. an average of six patients have to be treated with tamsulosin after ESWL to achieve clearance in one. Subgroup analysis for the six studies that used a dose of 0.4 mg tamsulosin showed a pooled risk difference of 19 (10–29)%. The expulsion time was analysed in three studies and the pooled mean difference was 8 (?3–20) days in favour of the tamsulosin group. Pain and analgesic usage was reported to be lower with tamsulosin. Adverse effects of tamsulosin, mainly dizziness, were reported in eight patients (3%).

CONCLUSIONS

Treatment with tamsulosin after ESWL appears to be effective in assisting stone clearance in patients with renal and ureteric calculi. To make a definite clinical recommendation to use tamsulosin after ESWL for renal and ureteric calculi, a high quality confirmatory trial is warranted.     

Renal injury during shock wave lithotripsy is significantly reduced by slowing the rate of shock wave delivery

OBJECTIVE: To assess the tissue protection afforded by simply reducing the rate of shock wave (SW) delivery, compared with studies in the pig in which SW lithotripsy (SWL)-induced vascular damage was significantly reduced by initiating treatment using low-amplitude SWs. MATERIALS AND METHODS: Juvenile pigs (6-7 weeks old) were treated with an unmodified lithotripter (HM3, Dornier Medical Systems, Kennesaw, GA) at either 120 or 30 SW/min. Treatment was to one kidney per pig, with SWs (2000, 24 kV) directed to a lower-pole calyx. After treatment, parenchymal haemorrhage was determined morphometrically and expressed as percentage of functional renal volume (%FRV). RESULTS: Kidneys treated at 120 SW/min had focal to extensive subcapsular haematomas. Parenchymal lesions were found only at the lower pole, but included regions within renal papillae and the cortex. Occasionally, damage extended across the full thickness of the kidney. The lesion in the pigs treated at 120 SW/min occupied a mean (sd) of 4.6 (1.7) %FRV. Kidneys of pigs treated at 30 SW/min showed no surface bleeding. Parenchymal haemorrhage was limited to papillae within the focal volume, and measured 0.08 (0.02) %FRV, a significant (P < 0.005) reduction in injury. CONCLUSIONS: Slowing the rate of delivery to 30 SW/min has a dramatic protective effect on the integrity of the kidney vasculature. This finding in our established pig model suggests a potential strategy to improve the safety of lithotripsy. As it was shown that a reduced SW rate also improves the efficiency of stone fragmentation, a slow rate appears to be a means to improve both the safety and efficacy of SWL.     

Effect of shock wave number on renal oxidative stress and inflammation

What’s known on the subject? and What does the study add? Oxidative stress and inflammation are tissue‐ and cell‐level components of shock wave lithotripsy (SWL)‐induced acute renal injury, which we recently showed to be localized principally to the medulla within the focal zone of the lithotripter. This study reports that the magnitude of the oxidative stress and inflammation observed in the medulla after SWL is dependent on the number of shock waves delivered to the kidney, indicating that this is a sensitive measure of renal injury caused by shock waves. OBJECTIVE To determine if the magnitude of the acute injury response to shock‐wave lithotripsy (SWL) depends on the number of SWs delivered to the kidney, as SWL causes acute renal oxidative stress and inflammation which are most severe in the portion of the kidney within the focal zone of the lithotripter. MATERIALS AND METHODS Pigs (7–8 weeks old) received 500, 1000 or 2000 SWs at 24 kV from a lithotripter to the lower pole calyx of one kidney. At 4 h after treatment the kidneys were removed, and samples of cortex and medulla were frozen for analysis of the cytokine, interleukin‐6, and for the stress response protein, heme oxygenase‐1 (HO‐1). Urine samples taken before and after treatment were analysed for the inflammatory cytokine, tumour necrosis factor‐α. For comparison, we included previously published cytokine data from pigs exposed to sham treatment. RESULTS Treatment with either 1000 or 2000 SWs caused a significant induction of HO‐1 in the renal medulla within the focal zone of the lithotripter (F2, 1000 SWs, P < 0.05; 2000 SWs, P < 0.001). Interleukin‐6 was also significantly elevated in the renal medulla of the pigs that received either 1000 or 2000 SWs (P < 0.05 and <0.001, respectively). Linear dose–response modelling showed a significant correlation between the HO‐1 and interleukin‐6 responses with SW dose (P < 0.001). Urinary excretion of tumour necrosis factor‐α from the lithotripsy‐treated kidney increased only for pigs that received 2000 SWs (P < 0.05). CONCLUSION The magnitude of renal oxidative stress and inflammatory response in the medulla increased with the number of SWs. However, it is not known if the HO‐1 response is beneficial or deleterious; determining that will inform us whether SWL‐induced renal injury can be assessed by quantifying markers of oxidative stress and inflammation.     

Pretreatment with low-energy shock waves reduces the renal oxidative stress and inflammation caused by high-energy shock wave lithotripsy

The purpose of this study was to determine if pretreatment of porcine kidneys with low-energy shock waves (SWs) prior to delivery of a clinical dose of 2,000 SWs reduces or prevents shock wave lithotripsy (SWL)-induced acute oxidative stress and inflammation in the treated kidney. Pigs (7–8 weeks old) received 2,000 SWs at 24 kV (120 SW/min) with or without pretreatment with 100 SWs at 12 kV/2 Hz to the lower pole calyx of one kidney using the HM3. Four hours post-treatment, selected samples of renal tissue were frozen for analysis of cytokine, interleukin-6 (IL-6), and stress response protein, heme oxygenase-1 (HO-1). Urine samples were taken before and after treatment for analysis of tumor necrosis factor-α (TNF-α). Treatment with 2,000 SWs with or without pretreatment caused a statistically significant elevation of HO-1 and IL-6 in the renal medulla localized to the focal zone of the lithotripter. However, the increase in HO-1 and IL-6 was significantly reduced using the pretreatment protocol compared to no pretreatment. Urinary excretion of TNF-α increased significantly (p < 0.05) from baseline for pigs receiving 2,000 SWs alone; however, this effect was completely abolished with the pretreatment protocol. We conclude that pretreatment of the kidney with a low dose of low-energy SWs prior to delivery of a clinical dose of SWs reduces, but does not completely prevent, SWL-induced acute renal oxidative stress and inflammation.     

Evaluation of a synchronous twin-pulse technique for shock wave lithotripsy: a prospective randomized study of effectiveness and safety in comparison to standard single-pulse technique

OBJECTIVE

To asses the efficacy and safety of bidirectional synchronous twin‐pulse extracorporeal shock wave lithotripsy (ESWL) compared with standard ESWL.

PATIENTS AND METHODS

Between March 2003 and December 2006, 240 patients with a radio‐opaque single renal stone of ≤25 mm were randomized to treatment either by the Twinheads (TH) lithotripter (FMD, Lorton, Virginia, USA) or the Dornier Lithotripter S (DLS, Dornier MedTech Europe GmbH, Germering, Germany). Before and after ESWL, urinary N‐acetyl‐B‐glucosaminidase (NAG) levels were assessed and patients were evaluated with dynamic MRI. The efficacy and complications were compared, with success defined as no residual fragments.

RESULTS

For stones of >10 mm the rate for the failure of disintegration was 13.3% for the DLS vs 1.4% for the TH (P = 0.009). For stones of ≤10 mm the stone‐free rate was 74.4% for the TH vs 67.7% for the DLS (P = 0.6), while for stones of >10 mm it was 78.1% and 66.7%, respectively (P = 0.14). The median (range) number of sessions in both groups was 2 (1–5). After ESWL urinary NAG levels were increased significantly in both groups; in the TH group it declined below the level before ESWL after 2 days, while in the DLS group it remained high after 7 days. In the DLS group four patients developed subcapsular or parenchymal haematoma after ESWL, vs none in the TH group. There was loss of corticomedullary differentiation after ESWL in three patients in the DLS group and only one in the TH group. In the DLS group there was a statistically significantly decrease in bilateral renal perfusion after ESWL, but no changes in the TH group.

CONCLUSIONS

Synchronous twin‐pulse ESWL has clinical advantages over standard ESWL in terms of safety and efficacy.     

sup 99m TECHNETIUM-DIMERCAPTO-SUCCINIC ACID RENAL SCAN IN THE EVALUATION OF POTENTIAL LONG-TERM RENAL PARENCHYMAL DAMAGE ASSOCIATED WITH EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY IN CHILDREN

Purpose

Extracorporeal shock wave lithotripsy (ESWL ^†) has been reported as efficient and safe in children. Because of reports of renal parenchymal damage in adults, this study was designed to assess the effects of ESWL in pediatric kidneys evaluated before and after treatment with^99m technetium dimercapto-succinic acid (DMSA) renal scan.

Materials and Methods

A total of 15 children, 9 months to 15 years old (mean age 6.5 years), underwent ESWL treatment for urolithiasis. Evaluation imaging included plain abdominal radiography, excretory urogram and/or renal sonography. DMSA renal scan was performed 24 hours before ESWL and at least 6 months after treatment.

Results

ESWL was performed in 1 session for 8 patients, 2 sessions for 6 and 3 sessions for 1, delivering a range of 600 to 3,000 shock waves per session. Treatment was successful in achieving stone-free status in 87% of the cases. Long-term followup (1 to 5 years) showed no blood pressure changes. On DMSA renal scan no acquired parenchymal scar was identified at least 6 months after ESWL treatment.

Conclusions

The efficacy of ESWL in treating pediatric urolithiasis is confirmed. Renal parenchymal trauma associated with ESWL does not appear to cause long-term lesions identifiable by DMSA renal scan.