Prevention of Lithotripsy-Induced Renal Injury by Pretreating Kidneys with Low-Energy Shock Waves

Abstract

Lithotripsy shock waves (SW) to one renal pole damage that pole but protect the opposite pole from the damage inflicted by another, immediate application of SW. This study investigated whether the protection (1) occurs when the first treatment causes no injury, (2) is caused by SW or injury, (3) exhibits a threshold, and (4) occurs when the same pole receives both treatments. Six-to 7-wk-old anesthetized female pigs were studied. The following groups were studied: group 1 (n ‫؍‬ 4), 2000 SW at 12 kV to one pole and 2000 SW at 24 kV (standard) to the opposite pole; group 2 (n ‫؍‬ 6), same as group 1 except 500 12-kV SW pretreatment; group 3 (n ‫؍‬ 8), 500 12-kV, 2000 standard SW, all to the same pole; and group 4 (n ‫؍‬ 8), same as group 3 except 100 12-kV SW pretreatment. Mean ؎ SD lesion size in group 1, first pole treated, was 0.66 ؎ 0.82% of functional renal volume (FRV; P < 0.05 versus 5.22 ؎ 3.6% FRV with no pretreatment [NP]; 95% confidence interval [CI] ؊7.0 to ؊2.1) and 0.50 ؎ 0.68% FRV in the opposite pole after 2000 standard SW (P < 0.05 versus NP; 95% CI ؊9.4 to ؊0.08). Mean lesion size (first pole) in group 2 was 0.020 ؎ 0.028% FRV (P < 0.01 versus NP; 95% CI ؊9.2 to ؊1.2) and 0.43 ؎ 0.54% FRV in the opposite pole after 2000 standard SW (P < 0.05 versus NP; 95% CI ؊8.8 to ؊0.82). Same-pole SW (groups 3 and 4) also protected. Mean lesion sizes were 0.28 ؎ 0.33% (P < 0.01 versus NP; 95% CI ؊8.0 to ؊1.9) in group 3 and 0.39 ؎ 0.48% FRV (P < 0.01 versus NP; 95% CI ؊8.2 to ؊1.7) in group 4. It is concluded that the pretreatment protocol substantially limits the renal injury that normally is caused by SWL and occurs when the pretreatment and standard SW are applied to the same pole. The threshold for the protection may be <100 SW.

CUA Guideline: Management of ureteral calculi

“…This also reduces renal injury by inducing renal vasoconstriction, which is protective in reducing the rate of renal hematomas. [31][32][33][34][35] An alternative strategy is to pre-treat the kidney with a series of low energy shocks and then pause treatment for a short period of time before resuming at higher energy levels. 31 Of note, if fragmentation is seen at lower energies it is not necessary to increase the energy any further.…”

Strategies to optimize shock wave lithotripsy outcome: Patient selection and treatment parameters

“…Another setting recommendation for SWL is pre-treating the stone at a low energy for 100-200 shock waves and then pausing for several minutes prior to going to a higher energy [50,51] . While this does not necessarily improve efficacy of SWL it does improve outcome by decreasing injury to the kidney [52][53][54] . Once the procedure begins, active monitoring of the stone location with continuous ultrasound or spot fluoroscopy every couple of minutes or every 100-200 shocks, will confirm that the target is still appropriately positioned within the treatment zone.…”

Using 300 Pretreatment Shock Waves in a Voltage Ramping Protocol Can Significantly Reduce Tissue Injury During Extracorporeal Shock Wave Lithotripsy

“…To illustrate what we mean by this statement, in the original study where we were just beginning to explore the idea of SW pretreatment protection, delivering 500 lowenergy SWs to a kidney followed by a pause and then 2000 high-energy SWs produced an average lesion size of 0.28% -0.33% FRV. 5 This value can be considered typical of kidneys protected from SWL injury. If we arbitrarily designate, for the sake of this illustration that only lesion values within two standard deviations from this mean as protected, then 0% of kidneys treated with only a clinical dose of 2000 high-energy SWs would be considered protected.…”

“…[1][2][3] We have also demonstrated that this injury can be significantly reduced (to *0.4% FRV) when the SWs are delivered at a slower pulse repetition rate, 2,4 or when a priming (pretreatment) dose of low-energy SWs is administered to a kidney followed by a 3-4 minute pause before delivery of a clinical dose of SWs (i.e., a voltage ramping protocol). 3,5 Although such protocols were effective at reducing injury, in both cases these protocol modifications increased the length of time needed to complete a lithotripsy treatment. As a practical matter, the time, which can be devoted to an individual patient's treatment, is limited and few urologists have the flexibility to adopt procedures that increase the length of time devoted to a lithotripsy session.…”

“…If we arbitrarily designate, for the sake of this illustration that only lesion values within two standard deviations from this mean as protected, then 0% of kidneys treated with only a clinical dose of 2000 high-energy SWs would be considered protected. 5 When 100 low-energy pretreatment SWs were delivered before administering 2000 high-energy SWs as part of our pause-less voltage ramping protocol, 25% of the treated kidneys would be considered protected. 6 Increasing the number of low-energy pretreatment SWs to 300 (in this study) or to 500 (reported earlier) resulted in an increase in the percentage of kidneys considered protected from 78% to 87%.…”