Shock Wave Lithotripsy Treatment Research Articles

Prefocal alignment improves stone comminution in shockwave lithotripsy.

The Dornier HM-3 machine continues to be one of the most effective lithotripters in use. However, tissue damage occurs in most, if not all, shockwave lithotripsy (SWL) treatments. Cavitation appears to contribute to desired stone comminution as well as to undesired tissue damage. Studies of cavitation in electrohydraulic shockwave lithotripters indicate that the greatest cavitation activity occurs, not at the geometric focus, F2, but at a site proximal to F2 by 1 to 3 cm. In clinical practice, however, stones are aligned with F2. In vitro stone comminution, hemolysis, and free-radical production were assessed along the focal axis, and pig kidneys treated with SWL in vivo were sectioned to determine the extent of hemorrhagic injury along the focal axis. Model gypsum stones received 200 shockwaves in vitro at 18 kV. At F2, the average number of fragments >1.5 mm was 1.3 +/- 0.5, and the weight loss was 11.3 +/- 1.1%. At 2 cm from F2 (F2-2 cm), these values increased to 4 +/- 2.8 and 16.1 +/- 4.2%, respectively. Samples of 10% hematocrit blood were similarly exposed. Hemolysis was equivalent at F2-2 cm (14.7 +/- 2.3%) and F2 (15.2 +/- 3%) but decreased significantly at all other positions. Samples of iodine solution received 1500 shockwaves at 20 kV. Hydroxyl radical production was greatest at F2-2 cm (0.384 +/- 0.035 microM) and decreased significantly distal to this position. The volume of tissue injury in pig kidneys was greatest with prefocal shockwave exposure. Stone comminution may be achieved more rapidly without greater tissue damage by a simple shift in stone alignment to F2-2 cm.

Assessment of patient effective radiation dose and associated radiogenic risk from extracorporeal shock-wave lithotripsy.

The aim of the present study was to calculate patient effective dose and associated radiogenic risk from fluoroscopy guided extracorporeal shock-wave lithotripsy procedures. Fluoroscopy required during extracorporeal shock-wave lithotripsy was classified in two types identified by beam orientation: antero-posterior and 30 degrees anterior-oblique projected exposures. Duration of each exposure was monitored in 124 patients undergoing extracorporeal shock-wave lithotripsy treatment for ureteral stones. The dose from a kidney-ureter-bladder radiograph and the dose per min of fluoroscopy along antero-posterior and anterior-oblique projections were measured at 13 organs/tissues using an anthropomorphic phantom and thermoluminescence dosimetry. A radio-opaque object was placed in the phantom to simulate an ureteral stone at the proximal and distal ureter. The total effective dose in male and female patients with proximal ureteral stones was 1.71 mSv and 1.82 mSv, respectively. The corresponding values for male and female patients with distal ureteral stones was 0.76 mSv and 1.62 mSv, respectively. In the United States, the theoretical sex-averaged radiogenic excess of fatal cancers was estimated to be 140 per million and 85 per million of patients treated for proximal and distal ureteral stone, respectively. The average radiogenic risk for genetic defect associated to treatments of proximal and distal ureteral stones was found to be 2.5 and 24.4 per million of births, respectively. The radiation risk from a typical fluoroscopy guided extracorporeal shock-wave lithotripsy treatment of ureteral stones is low. Presented data may be used to determine patient effective dose from extracorporeal shock-wave lithotripsy procedures performed in any laboratory.

Extracorporeal shock wave lithotripsy treatment in paraplegic patients with bladder stones.

Spinal cord injury patients are at increased risk of developing urolithiasis and many will require treatment, most commonly with extracorporeal shock wave lithotripsy (ESWL). We examined 20 consecutive spinal cord injury patients (all male) undergoing ESWL for the treatment of bladder stones between April 1992 and May 2000. The mean number of shock waves administered in these 20 patients was 3600 and the shock power was 19 kW/s. All patients were treated without anesthesia. After ESWL, the bladder was irrigated with povidone iodine solution and stone fragments were evacuated through a 22F endoscopic sheath. All patients became stone-free after ESWL. Stone fragments were observed in the urethra of 3 patients, which were removed by urethroscopy. No major complication was observed; however, 5 patients had minor hematuria (which subsided within 24 h) and subfebrile fever (37.2-37.5 degrees C). ESWL and transurethral bladder irrigation is a safe, effective and simple modality for the treatment of bladder stones in spinal cord injury patients.

Factors associated with failure of extracorporeal shock-wave lithotripsy for ureteral stones using Dornier lithotripter U/50.

In the present series of 170 patients who underwent extracorporeal shock-wave lithotripsy (SWL) treatment for ureteral stones, the authors determine which patients with ureteral stones had an unsuccessful outcome. The records of 170 patients with ureteral stones who were treated with SWL using the Dornier lithotriptor U/50 (EMSE 140) between January 1998 and December 1999 were retrospectively investigated. One hundred and thirty-one patients were treated with SWL alone (single session, n = 98; multiple session, n = 33) and 39 patients required auxiliary treatment due to failure of SWL (33 with transurethral ureterolithotripsy (TUL), one with open lithotomy, and five with residual fragments who were followed up). These two groups were compared using multivariate logistic regression analysis. Lower ureteral stones and stones more than 12 mm in diameter were associated with a poor outcome of SWL. There were no significant differences in age, gender, number of stones, JJ stent placement, and degree of ureteral obstruction due to the stone between the two groups. The odds ratios of lower ureteral stones and stones > or = 12 mm were 4.18 and 2.57, respectively. Patients with distal ureteral stones and/or stones more than 12 mm in diameter were difficult to treat successfully with SWL. Alternatives such as TUL should possibly be considered as a first-line therapy for these stones.

Is measurement of stone surface area necessary for SWL treatment of nonstaghorn calculi?

The size of urinary tract stones is usually assessed by the longest diameter (LD) alone. Logically, however, two-dimensional measurement of the stone surface area (SSA) susceptible to shockwaves would give more useful information for the planning of treatment by extracorporeal shockwave lithotripsy (SWL). This has been shown for staghorn calculi. The aim of this study was to determine for nonstaghorn kidney and ureter stones whether the LD alone identifies as reliably a subgroup of patients with a stone of a certain size as does the SSA. Furthermore, we sought to determine whether the LD alone indicates as reliably the number of patients who would be rendered stone free after one SWL session within a certain subgroup as would the SSA. Retrospectively, SWL treatment and radiographic data of 330 patients who had undergone SWL for a single stone were analyzed. Ureteral stones were significantly smaller on average, and ureteral stone patients needed fewer SWL treatment sessions and fewer shockwaves to become stone free. Stratification of both kidney and ureteral stones by either LD or SSA resulted in comparable groups of patients. There were no significant differences in patient, stone, or treatment data. More importantly, the stone-free rates after one treatment did not differ significantly. The LD does accurately reflect the size of a nonstaghorn kidney or ureteral stones. Therefore, the measurement of LD, as generally practiced, appears clinically sufficient and appropriate for the assessment of stone size prior to SWL in both kidney and ureteral stones.

Percutaneous nephrolithotomy in the management of pediatric renal calculi.

In the era of extracorporeal shockwave lithotripsy (SWL), there are still some patients who will require percutaneous nephrolithotomy (PCNL). Our experience with this procedure is reviewed and discussed. Fifty five patients with a mean age of 7.9 years (10 months-14 years) underwent 67 PCNL procedures on 62 renal units between September 1997 and April 2001. Of the patients, 13 had previous open renal surgery, 4 had a solitary kidney, 4 were SWL failures, 2 had osteogenesis imperfecta, one had anuria secondary to bilateral calculi, 2 had poorly functioning kidneys, and 1 had cystinuria (complete staghorn calculus). One disabled patient with neurologic disorders who had multiple stones underwent PCNL in order to decrease the stone burden and to improve the kidney function. Operations were performed under the guidance of monoplane fluoroscopy. Pneumatic or ultrasonic lithotripsy and forceps extraction were used with a rigid nephroscope or ureteroscope (as an alternative instrument in small-caliber tracts). Excluding the patient with neurologic disorders, 53 of the renal units (86.9%) were stone free at the time of discharge, and the success rate was 96.7%, with six patients having insignificant residual fragments after the procedure. In one patient, open surgery was required, and the other patient was sent for SWL treatment. There was no contiguous organ injury, but in 16 procedures (23.9%), intraoperative hemorrhage was seen, and blood transfusions were required. Pediatric urolithiasis is usually a result of metabolic abnormalities and urinary tract infection, and there is always a risk of recurrence that may necessitate multiple additional intervention. Therefore, PCNL must be considered in selected cases by urologists who are experienced in adult percutaneous procedures.

IN VIVO ASSESSMENT OF FREE RADICAL ACTIVITY DURING SHOCK WAVE LITHOTRIPSY USING A MICRODIALYSIS SYSTEM: THE RENOPROTECTIVE ACTION OF ALLOPURINOL

Shock wave lithotripsy is believed to cause renal damage directly through cellular injury from high energy shock waves and indirectly through vascular injury and resultant ischemia, which gives rise to oxygen free radical compounds. The transient and volatile nature of free radicals and derived products makes their detection difficult. Moreover, certain medications may provide a protective effect against shock wave lithotripsy induced renal parenchymal injury. We introduced an innovative microdialysis system for in vivo sampling of interstitial fluids that can be analyzed for free radical mediated lipid peroxidation products after shock wave lithotripsy treatment in the swine model. In addition, this system was used to test the antioxidant or renoprotective action of allopurinol. Ten juvenile swine were assigned to a nonmedicated control group that underwent shock wave lithotripsy or to a group that was premedicated with allopurinol before shock wave lithotripsy. Each group of animals underwent shock wave lithotripsy to the lower pole of the right kidney and received a total of 10,000 shock waves. Dialysate fluid was collected at 1,000-shock wave increments via probes surgically implanted into the lower pole of the right and left kidneys before lithotripsy. Samples were immediately preserved in liquid nitrogen and subsequently analyzed for the presence and concentration of conjugated diene levels, a measure of lipid peroxidation. Five additional juvenile swine were assigned to a sham treated group that did not undergo shock wave lithotripsy. Dialysate fluid was collected from the lower pole of the right and left kidneys to establish baseline or pre-lithotripsy levels of conjugated dienes. After shock wave lithotripsy conjugated diene levels increased almost 100-fold over that in the right kidneys of the nonmedicated control group. The difference was statistically significant compared to levels in the contralateral untreated kidneys (p <0.01). Right kidneys in the group premedicated with allopurinol did not demonstrate an increase in conjugated diene levels during shock wave lithotripsy. The results of this study confirm shock wave lithotripsy induced free radical activity as well the antioxidant and protective nature of allopurinol. The newly described microdialysis system enables real-time sampling of interstitial fluids during shock wave lithotripsy. It represents a unique method for assessing free radical formation and evaluating the protective effects of additional antioxidant medications.

PROSPECTIVE RANDOMIZED TRIAL COMPARING SHOCK WAVE LITHOTRIPSY AND URETEROSCOPY FOR MANAGEMENT OF DISTAL URETERAL CALCULI

We compared the efficacy of shock wave lithotripsy and ureteroscopy for treatment of distal ureteral calculi. A total of 64 patients with solitary, radiopaque distal ureteral calculi 15 mm. or less in largest diameter were randomized to treatment with shock wave lithotripsy (32) using an HM3 lithotriptor (Dornier MedTech, Kennesaw, Georgia) or ureteroscopy (32). Patient and stone characteristics, treatment parameters, clinical outcomes, patient satisfaction and cost were assessed for each group. The 2 groups were comparable in regard to patient age, sex, body mass index, stone size, degree of hydronephrosis and time to treatment. Procedural and operating room times were statistically significantly shorter for the shock wave lithotripsy compared to the ureteroscopy group (34 and 72 versus 65 and 97 minutes, respectively). In addition, 94% of patients who underwent shock wave lithotripsy versus 75% who underwent ureteroscopy were discharged home the day of procedure. At a mean followup of 21 and 24 days for shock wave lithotripsy and ureteroscopy, respectively, 91% of patients in each group had undergone imaging with a plain abdominal radiograph, and all studies showed resolution of the target stone. Minor complications occurred in 9% and 25% of the shock wave lithotripsy and ureteroscopy groups, respectively (p value was not significant). No ureteral perforation or stricture occurred in the ureteroscopy group. Postoperative flank pain and dysuria were more severe in the ureteroscopy than shock wave lithotripsy group, although the differences were not statistically significant. Patient satisfaction was high, including 94% for shock wave lithotripsy and 87% for ureteroscopy (p value not significant). Cost favored ureteroscopy by $1,255 if outpatient treatment for both modalities was assumed. Ureteroscopy and shock wave lithotripsy were associated with high success and low complication rates. However, shock wave lithotripsy required significantly less operating time, was more often performed on an outpatient basis, and showed a trend towards less flank pain and dysuria, fewer complications and quicker convalescence. Patient satisfaction was uniformly high in both groups. Although ureteroscopy and shock wave lithotripsy are highly effective for treatment of distal ureteral stones, we believe that HM3 shock wave lithotripsy, albeit slightly more costly, is preferable to manipulation with ureteroscopy since it is equally efficacious, more efficient and less morbid.

In vivo quantitation of regional versus systemic SWL-induced free-radical activity

Renal tissue injury in shock wave lithotripsy (SWL) may be attributed directly to vascular trauma and indirectly to ischemia-reperfusion with resultant free-radical formation. We have employed a microdialysis system to assess areas of renal injury in relation to the site of SWL treatment. Swine were assigned to a control group (N=3) and a SWL-treated group (N=3). Microdialysis probes were inserted into the parenchyma of the lower pole, upper pole of right kidney, and the lower pole of left kidney. Seventy-two hours following probe insertion, baseline dialysate samples were collected, after which SWL was administered exclusively to the right kidney lower pole in the treated group, using a Dornier Compact S lithotripter at its highest intensity. Dialysate samples were collected every 1000 shocks. It was found that SWL caused a significant increase in free-radical activity, as measured by lipid peroxidation, in the right lower pole, followed by a moderate increase in the right upper pole. Yet, no free-radical activity was noted in the left kidney. These findings suggest that SWL-induced free-radical activity is localized and confined to the ipsilateral kidney. There does not appear to be systemic circulating nephrotoxic factors following SWL treatment. [Work supported by NIH.]

Shock Wave Lithotripsy Treatment of Radiolucent Ureteric Calculi with the Help of Contrast Medium

Objective: Extracorporeal shock wave lithotripsy (SWL) treatment of radiolucent ureteric calculi (UC) is hampered by the reduced visibility of the stone. Intravenous contrast medium (IV–CM) administration may overcome this problem by indirectly depicting the localisation of the stone. However, IV–CM administration bears known risks. The aim of this study was to compare the clinical outcome after SWL in two representative groups of patients with either radiolucent or radio–opaque UC. Methods: Two groups of patients, 156 with a radiolucent UC and 203 with a radio–opaque UC, were assessed with regard to age, gender, treatment modalities, auxiliary measures, complications, stone properties and stone–free rate 3 months after treatment. Results: Both groups were comparable with regard to epidemiology, treatment and clinical outcome. In both groups, stone–free rates were well within the percentages described by other investigators. There were no adverse reactions to CM. Conclusions: The clinical outcome of SWL treatment for radiolucent ureter stones does not differ from that for radio–opaque ureter stones. Being a non–invasive treatment, SWL with the help of IV–CM administration should be the first–line therapy for radiolucent ureter stones. Although awareness of possible adverse reactions to CM is mandatory, the risk remains small.

Extracorporeal Shock Wave Lithotripsy in Ureteral and Kidney Malformations

Introduction: Extracorporeal shock wave lithotripsy (SWL) has long been accepted worldwide in the treatment of kidney stone disease. Upper ureter calculi in ureteral and kidney malformations are rather frequent (10–25%). The aims of this retrospective study were to determine whether malformations might impair fragment expulsion. Material and Methods: From 1986 to 1995, 203 patients with ureteral and kidney malformations were treated and followed up for a minimum of 1 year to a maximum of 9 years. Malformations included: ureteropelvic junction stenosis, horseshoe kidney, renal malrotation, renal ectopia, duplicated ureter, nonobstructive megaureter, medullary sponge kidney and caliceal diverticula. As pretreatment workup, all patients underwent conventional studies prior to SWL treatment: X-rays, renal ultrasound, intravenous pyelography, routine blood tests and urinalysis. All examinations were repeated at regular intervals for the first 6 months. Patients with metabolic disorders were excluded from the study. We also excluded patients with a follow-up of under 1 year. We considered three groups of patients: (1) stone-free patients at plain X-rays and ultrasound; (2) >90% elimination, i.e. stone-free patients at plain X-rays and positive at ultrasound; (3) patients with residual fragments at plain X-rays and ultrasound. Results: 96 (55%) patients were in group 1 (stone free), 40 (19%) were in group 2 (>90% elimination) and 67 (26%) were in group 3 (residual). Residual stones were more frequent in patients with medullary sponge kidney (82%). In patients with renal ectopia the residual stone rate accounted for only 13% of cases. Conclusions: There is evidence that SWL should always be offered to patients with ureteral and kidney malformations. These patients should however be considered at high risk for recurrences and so they need to be carefully followed up.

LOW SUCCESS RATE OF REPEAT SHOCK WAVE LITHOTRIPSY FOR URETERAL STONES AFTER FAILED INITIAL TREATMENT

We determined the number of shock wave lithotripsy treatments that should be given for a single ureteral stone before alternate modalities are used. We compared the stone-free rate of initial shock wave lithotripsy for ureteral calculi with that of subsequent treatments. We evaluated 1,593 ureteral stones treated with the Dornier MFL 5000 lithotriptor* from January 1, 1994 to September 1, 1999 using various parameters associated with treatment outcome. The stone-free rate after initial treatment was 68% (1,086 of 1,593 stones), which decreased to 46% (126 of 273) after re-treatment 1. We observed a further decrease in the stone-free rate after re-treatment 2 to 31% (19 of 61 stones, p = 0.001). The cumulative stone-free rate increased to 76% (1,212 of 1,593 stones) after 2 treatments and to 77% (1,231 of 1593) after 3. The stone-free rate for stones 10 mm. or less was significantly better than that of stones 11 to 20 mm. initially (64% versus 43%) and after re-treatment (49% versus 37%). A ureteral stent decreased the stone-free rate of initial treatment and re-treatment 1 by 12% and 14%, respectively (p = 0.001). After initial treatment the stone-free rate of the upper and mid ureter was significantly higher than that of the lower ureter. Patient weight had no significant impact on success in either group. The stone-free rate of re-treating ureteral calculi with shock wave lithotripsy decreases significantly after the initial treatment. These findings imply that ureteroscopic management of ureteral stones may be better than shock wave lithotripsy after initial shock wave lithotripsy fails.

Extracorporeal shock wave lithotripsy for a ureteral stone in crossed fused renal ectopia

A 63-year-old woman presented with right flank pain and macroscopic hematuria. A plain film showed a calcific shadow on the right iliac bone. On excretory urography, the right kidney was seen in the normal position, but the left kidney was not. Bilateral retrograde pyelogram revealed the S-shaped kidney and mild obstruction from a 12 x 5 mm calculus in the proximal ureter of the crossed kidney. The patient was successfully treated with in situ extracorporeal shock wave lithotripsy (ESWL) treatment and is stone free at 1 month follow up. We believe this is the first case of successful ESWL in a crossed kidney.

Bubble translation due to radiation force in SWL

The clustering of cavitation bubbles may lead to enhanced stone comminution and influence the extent of tissue damage during shock wave lithotripsy (SWL) treatment. Recent research has focused on changing the SWL pulse, or timing between pulses, to intensify or mitigate collapse or localize these clusters. Such research has targeted radial, not translational motion. We investigate whether bubble translation due to radiation force is sufficiently large to influence cluster formation. The translational dynamics of a single spherical bubble were modeled according to the formulation proposed by Watanabe and Kukita [Phys. Fluids 5(11) (1993)]. After radius-time data were obtained using the Gilmore equation, translational motion was calculated by numerical integration of the Watanabe equation. Calculations were performed for a range of bubble sizes (R0=2–20 μm) and pressure rise times (10−9–10−7 s). The results show that, during bubble growth and collapse induced by a single pulse or two pulses with microsecond delays, bubble translations are ∼0.1 mm. Although bubble translation from a single pulse may not have a noticeable effect on bubble distribution, the effect may be cumulative for the 1000+ shots fired during clinical SWL treatment. [Work supported by NIH DK43881, NSF, CRDF, and FIRCA.]

The impact of the geometry of the lithotriptor aperture on fragmentation effect at extracorporeal shock wave lithotripsy treatment.

The aim of this study was to determine the impact of the aperture size of an electro-hydraulic lithotriptor on the fragmentation effect. We also wanted to investigate whether a potential change in the capacitance of the pulse forming network (PFN), at a certain energy level, might have an impact on fragmentation rate. Two different apertures with a diameter of 23 and 17 cm respectively were compared using two different values of total PFN capacitance: 50 nF and 80 nF. Model stones of similar size and weight were fragmented. The number of shots for complete fragmentation or the grade of fragmentation after a certain number of shots was measured. This study shows that for the shock wave system used, the 23-cm aperture seems to provide more effective fragmentation as function of the number of shots compared with the 17-cm aperture at the same energy level. Furthermore, a minor change in the PFN capacitance between reasonable limits does not affect the fragmentation efficiency. This article also highlights the fact that it is not relevant simply to compare the voltage level given in the shots in extracorporeal shock wave lithotripsy treatment between different lithotriptors.

Two-year experience with ureteral stones: extracorporeal shockwave lithotripsy v ureteroscopic manipulation.

Extracorporeal shockwave lithotripsy (SWL) and ureteroscopic manipulation became the standard treatments for ureteral stones in recent years. There still exists significant debate as to the most appropriate treatment modality for ureteral stones. During a period of 2 years, from January 1994 to December 1995, 651 patients with ureteral stones were treated, and 589 patients were retrospectively reviewed, excluding 62 patients with incomplete follow-up. Four hundred forty-two patients were treated with SWL using the MPL 9000 with ultrasonic guidance and 115 patients with ureteroscopic manipulations using 7.9F to 11.5F rigid and semirigid ureteroscopes. In SWL treatments, the overall stone-free rate was 74.7% with one session. The stone-free rate was significantly affected by the size of stones, being 83.6% when the stone was <1.0 cm and 42.1% when the stone was >1.0 cm. The stone-free rate after a second SWL session was 84.4% and was 90.3% after a third session. The stone-free rates according to the site of the stone were 72.4 (proximal), 70.0 (mid), and 80.2% (distal) after a single session. In ureteroscopic manipulation, an overall stone-free rate of 87.8% was obtained regardless of the size of the stones. The success rates according to the location of stones were 75.0 (proximal), 94.6 (mid), and 86.4% (distal). Open ureterolithotomy was performed in 32 patients, with a 100% success rate. In our study, the size of the stones was the most important factor influencing the success rate of SWL treatment. We consider ureteroscopic manipulation as the first-line treatment modality when the stone is >1.0 cm, especially if it is in the distal ureter. Proper selection of patients for in situ SWL or ureteroscopy would improve the results of initial treatment.

Calyceal stones: fate of shock wave therapy with respect to stone localization.

In a retrospective analysis the results of extracorporeal shock wave lithotripsy (ESWL) treatment were evaluated in patients with renal stones according to calyceal localization of treated stones. The 198 patients who underwent ESWL with the Dornier MPL 9000 were analyzed for success rate, complication rate, residual fragments, regrowth and recurrence rates. Totally 210 calyceal calculi located in different portions of the kidney have been comparatively evaluated. No major complications were noted during or after ESWL. Some minor complications such as flank pain, renal colic, haematuria were observed. Flank pain was observed during ESWL treatment especially in patients with upper calyceal stones. Although stone-free and residual fragment rates were similar in pelvic, upper and middle calyces, patients with lower calyceal and pelvicalyceal stones had high residual fragment rate and lower stone-free rate. Patients with stones in the lower calyces or pelvicalyces had high recurrence and regrowth rates (p < 0.05). ESWL has been considered as the optimal treatment modality for most upper urinary tract calculi. It is especially effective in patients with pelvic, upper and middle calyceal stones. Patients with lower calyceal stones often failed to eliminate the fragments, hence had high recurrence and regrowth rates.

Significant elevation of urinary 28-kD calbindin-D and N-acetyl-beta-D-glucosaminidase levels in patients undergoing extracorporeal shock wave lithotripsy.

Calbindin-D, a vitamin D-dependent calcium binding protein with a molecular mass of 28 kD, is found predominantly in distal renal tubules and central nervous system tissues in man. We have developed a highly sensitive enzyme immunoassay for human 28-kD calbindin-D and demonstrated its advantages as a new marker for damage to distal renal tubules. Urinary N-acetyl-beta-D-glucosaminidase (NAG), a lysosomal enzyme of the proximal renal tubules, is another segment-specific indicator of renal damage. To clarify whether both proximal and distal renal tubules are similarly affected by extracorporeal shock wave lithotripsy (SWL) treatment, urinary 28-kD calbindin-D and NAG were measured before, then immediately, 2 and 24 hours after SWL in 17 renal lithiasis patients. Levels of urinary calbindin-D were markedly elevated immediately and 2 hours after SWL and then decreased. In sera, levels of calbindin-D also increased, closely correlated with the changes in urinary values. Levels of urinary NAG were also significantly elevated immediately after SWL and then decreased. The results indicate that damage to both proximal and distal renal tubules occurs simultaneously with SWL and that the two markers can be applied as sensitive indicators of such side effects and their alleviation with protective agents.

First in vitro experiments using a new reflector to concentrate shock waves for extracorporeal shock wave lithotripsy

Electrohydraulic lithotripters to perform extracorporeal shock wave lithotripsy (ESWL) treatments use symmetrical reflectors in order to concentrate the energy generated in one of their foci (F1). The new reflector presented here was designed in an attempt to increase the efficiency of ESWL. It is obtained by combining sectors of two rotationally symmetric ellipsoidal reflectors with different separations between their foci F1 and F2. These sectors are joined together in such a way that the F1 foci coincide, creating a separation between the F2 foci. The purpose is to temporally and spatially dephase the shock wave generated at F1. This is achieved because the initial shock wave is divided, by reflection, into two shock fronts converging toward two, rather than one, F2 foci. Pressure measurements, and in vitro experiments using kidney-stone models and dog kidneys, indicate that the new design could be more efficient in breaking up renal stones, without producing more tissue damage. The performance of the new reflector was compared with one having the geometry of a Dornier HM3 (nonmodified) reflector. Both reflectors were installed separately in an electrohydraulic experimental shock wave generator (MEXILIT II). [Work supported by DGAPA IN502694, UNAM.]

Cardiac Arrhythmias with External Fixed-Rate Signal Generators in Shock Wave Lithotripsy with the Medstone Lithotripter

Objectives. To evaluate the incidence and outcome of cardiac arrhythmias associated with an external fixed-rate generator and the Medstone lithotripter with regard to stone location, anesthesia type, patient age, and gender. Methods. Data were obtained on 933 patients who underwent shock wave lithotripsy (SWL) with the Medstone lithotripter. Patients were randomly divided into two study groups, including those with pre-existing cardiac disease, hypertension, and cardiac medications. Group 1 (576 patients) were treated with the external fixed-rate signal generator (cardiac simulator). Group 2 (357 patients) underwent electrocardiogram-gated SWL (no simulator). All patients were monitored for arrhythmias during SWL. Patients who developed arrhythmias on the simulator were converted to gated SWL. Results. In group 1, 463 patients (80%) had no arrhythmias during treatment, whereas 113 patients (20%) developed cardiac arrhythmias (primarily premature ventricular contractions [PVCs]) and were successfully converted to gated SWL. Only 1 patient in group 2 (0.3%) had a documented arrhythmia (PVC). Group 1 patients who developed arrhythmias with a cardiac simulator were more likely to have renal rather than ureteral stones. Chi-square analysis showed a significant correlation between patients with and without arrhythmias in group 1 with regard to stone location ( P <0.0001). In group 1, regional anesthesia, intravenous anesthesia, and general anesthesia had an arrhythmia rate of 14%, 27%, and 38%, respectively. The only patient in group 2 who developed arrhythmias was under general anesthesia. The differences between groups 1 and 2, with regard to anesthesia type and arrhythmia, were statistically significant ( P <0.001). No patients required additional medical therapy or hospitalization for cardiac events, and all patients safely completed the SWL treatment. Conclusions. With careful monitoring and adequate precautions, external fixed-rate signal generators are safe, effective methods for pacing the Medstone shock wave lithotripter and probably other extracorporeal shock wave lithotripters.