New Onset Hypertension After Extracorporeal Shock Wave Lithotripsy: Age Related Incidence and Prediction by Intrarenal Resistive Index

A Prospective Randomized Study Comparing the Effect of Different Kidney Protection Treatment Protocols on Acute Renal Injury After Extracorporeal Shockwave Lithotripsy

OBJECTIVES

To perform a prospective study to evaluate the renal protective effects of ramping protocol and pause protocol for extracorporeal shockwave lithotripsy (SWL) in human subjects.

PATIENTS AND METHODS

Three hundred twenty patients with solitary renal stone <15 mm were randomized to receive one of four protocols: (1) 80% power from beginning until the end of treatment; (2) the first 100 shockwaves (SWs) at 40% power, and then 80% power until the end of treatment; (3) the first 100 shocks at 40% power, followed by a 3-minute pause, and then further SWs at 80% power until the end of treatment; and (4) the first 100 shocks at 80% power, followed by a 3-minute pause, and then further SWs at 80% power until the end of treatment. The primary endpoint was the incidence of renal hematoma assessed by imaging on day 2. Spot urine samples were also collected before and after treatment for acute renal injury marker measurement.

RESULTS

The baseline information and treatment parameters of the four groups were comparable. The overall incidence of hematoma formation was 7.69% (24 patients). The number of patients developing hematoma in the four groups was 8 (10.26%), 7 (8.97%), 6 (7.59%), and 3 (3.90%), respectively, and the incidence of hematoma among the four groups was not significantly different. Only patient's body mass index and mean blood pressure during treatment were predictors for hematoma formation. There was also no significant difference in changes in the levels of all markers and complication and hospitalization rates between the four groups.

CONCLUSION

Comprehensive assessment of clinical parameters, imaging results, and urinary markers showed no obvious improvement in post-SWL renal insult by either protocol.

Fabrication of SU-8 based Capacitive Micromachined Ultrasonic Transducer for low frequency therapeutic applications

In this paper we present a simple post-CMOS compatible sacrificial release method of fabricating SU-8 based Capacitive Micromachined Ultrasonic Transducer (CMUT) for low frequency therapeutic applications. CMUTs fabricated with Silicon Nitride and Silicon Dioxide lay constraints in terms of area and power consumption especially in the low frequency range. Fabrication of these devices need complex high temperature processes that makes them incompatible for post-CMOS processing. Analytical modeling shows that SU-8 based CMUT consumes less area (below 25%) and power compared to Silicon Nitride and Silicon Dioxide based CMUTs. The proposed fabrication method overcomes inherent disadvantages of sacrificial release method by providing uniformity in air gap and reducing the possibility of stiction.

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. <or=39, 40-59 and >or=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 >or=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 >or=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 (>or=60 years). Measurement of RI with Doppler techniques might provide useful information for the clinical diagnosis of renal damage.

Is extracorporeal shock wave lithotripsy the preferred treatment option for elderly patients with urinary stone? A multivariate analysis of the effect of patient age on treatment outcome

OBJECTIVES

To investigate the effect of patient age on the stone-free rate (SFR) in patients with urinary calculi treated by extracorporeal shockwave lithotripsy (ESWL).

PATIENTS AND METHODS

In all, 2192 solitary radio-opaque urinary stones of 5-15 mm were identified in adult patients receiving primary ESWL. Patients were divided into three age groups, i.e. < or = 40, 41-60 and >60 years (579, 1026 and 587 patients, respectively). Multiple logistic regression was used to assess the effect of age and other possible predicting factors (gender, stone characteristics, e.g. side, site and size, and the type of lithotripter used) on the SFR at 3 months after treatment.

RESULTS

The overall adjusted odds ratios (95% confidence interval) for the SFR for those aged 41-60 and >60 years (taking those aged < or= 40 years as the reference) were 0.708 (0.573-0.875; P = 0.001) and 0.643 (0.506-0.818; P < 0.001). However, if the patients were divided into those with renal or ureteric stones, only the SFR of the former was affected by age, and the adjusted odds ratios were 0.665 (0.512-0.864; P = 0.002) and 0.629 (0.470-0.841; P = 0.002), respectively. Ageing had no effect on the SFR for ureteric stones.

CONCLUSION

The SFR after ESWL for renal stones, but not ureteric stones, was significantly lower in older patients. Further studies on the effects of ageing on renal stone clearance after ESWL are needed to improve stone management in the elderly population.

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.

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.

Shockwave lithotripsy: dose-related effects on renal structure, hemodynamics, and tubular function

BACKGROUND AND PURPOSE

Shockwave lithotripsy (SWL) predictably damages renal tissue and transiently reduces function in both kidneys. This study characterized the effects on renal function of a supraclinical dose of shockwaves (SWs) (8000) in porcine kidneys and tested the hypothesis that such excessive treatment would intensify and prolong the resulting renal impairment.

MATERIALS AND METHODS

Pigs aged 6 to 7 weeks were anesthetized and assigned to one of three groups. Groups 1 (N=8) and 2 (N=6) each received 8000 SWs at 24 kV (Dornier HM3) to the lower-pole calix of one kidney. Group 3 (7 pigs) received sham treatment. Renal function was monitored for the first 4 hours after SW treatment in Group 1 and for 24 hours in Group 2. Plasma renin activity was measured in Groups 2 and 3.

RESULTS

The renal lesions produced by 8000 SWs comprised 13.8%+/-1.4% of the renal mass. In the 4-hour protocol, this injury was associated with marked reduction of the glomerular filtration rate (GFR), renal plasma flow (RPF), and urinary sodium excretion in both kidneys, although fractional sodium excretion was reduced only in the shocked kidneys. In the 24-hour protocol, GFR and RPF remained below baseline in shocked kidneys at 24 hours. Evidence of progressive ischemic injury was noted in shocked tissue at 24 hours after SW treatment.

CONCLUSIONS

These findings support the hypothesis that the severity of the renal injury caused by SWL is related to the number of SWs administered and demonstrate the connection in this relation between renal structure and function.

Color Doppler sonography examination of partially obstructed kidneys associated with ureteropelvic junction stone before and after percutaneous nephrolithotripsy: Preliminary report

AIM

To evaluate resistive index (RI) changes before and after unilateral percutaneous nephrolithotripsy in chronic partially obstructed kidneys due to ureteropelvic junction (UPJ) stones.

METHODS

Intrarenal RI of obstructed and contralateral normal kidneys of 18 patients were recorded immediately before the operations and at postoperative days 1, 7 and 30. Postoperative RI measurements were compared with baseline values for all patients without grouping and separately for different groups according to the preoperative RI value of the obstructed kidney.

RESULTS

Mean age and symptom duration were 27.5 years and 43.8 weeks, respectively. Preoperatively and at all postoperative controls, kidney diameters and renal parenchyma thicknesses were normal in all patients. Mean RI of obstructed kidneys decreased from 0.68 to 0.63 for all patients (P=0.032), from 0.64 to 0.63 for those with preoperative RI<0.70 (P=0.850) and from 0.73 to 0.62 for those with preoperative RI>or=0.70 (P=0.001). In patients with preoperative RI>or=0.70 in obstructed kidney, significant RI decreases were recorded at postoperative day 7 and RI differences between obstructed and contralateral kidneys disappeared after then. No difference was present pre- and postoperatively between the mean RI of obstructed and contralateral kidneys of the patients with RI<0.70. Mean RI of contralateral kidneys were normal preoperatively and showed no significant change postoperatively.

CONCLUSIONS

Preoperative RI levels may indirectly reflect the presence of functionally significant obstruction in chronic obstructed kidneys related to UPJ stones. Patients with RI>or=0.70 may have a good indication for a surgical approach. Normalization of high RI occurs rapidly after percutaneous nephrolithotripsy.

Shockwave Lithotripsy: Anecdotes and Insights

Shockwave lithotripters have evolved considerably since the introduction of the Dornier HM3 machine 20 years ago. Although shockwave lithotripsy (SWL) remains the preferred treatment for the majority of symptomatic upper urinary-tract calculi, newer lithotripters are not as effective and may have a higher risk of side effects. Lack of progress in lithotripter evolution is attributable to inadequate understanding of how and why shockwaves produce effects on stone and tissue. Current knowledge suggests that stones fragment by the mechanisms of compression fracture, spallation, squeezing, and acoustic cavitation, while tissue damage from shockwaves is secondary to cavitation and non-cavitational forces such as sheer stress. It appears likely that most tissue damage from shockwaves is caused by cavitation. As the understanding of SWL matures, new lithotripter designs may emerge that truly represent an improvement on the original Dornier HM3 machine.