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.

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.

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.