Renal Protection Phenomenon Observed in a Porcine Model After Electromagnetic Lithotripsy Using a Treatment Pause

Abstract

Purpose: Pretreating the kidney with 100 low-energy shock waves (SWs) with a time pause before delivering a clinical dose of SWs (Dornier HM-3, 2000 SWs, 24 kV, and 120 SWs/min) has been shown to significantly reduce the size of the hemorrhagic lesion produced in that treated kidney, compared to a protocol without pretreatment. It has been assumed that a similar reduction in injury will occur with lithotripters other than the HM-3, but experiments to confirm this assumption are lacking. In this study, we sought to verify that the lesion protection phenomenon also occurs in a lithotripter using an electromagnetic shock source and dry-head coupling. Materials and Methods: Eleven female pigs were placed in a Dornier Compact S lithotripter where the left kidney of each animal was targeted for lithotripsy treatment. Some kidneys received 2500 SWs at power level (PL) = 5 (120 SWs/min) while some kidneys were pretreated with 100 SWs at PL = 1, with a 3-minute time pause, followed immediately by 2500 SWs at PL = 5 (120 SWs/min). Lesion size analysis was performed to assess the volume of hemorrhagic tissue injury created by each treatment regimen (% functional renal volume). Results: Lesion size fell by 85% (p = 0.01) in the 100 SW pretreatment group compared to the injury produced by a regimen without pretreatment. Conclusions: The results suggest that the treatment pause protection phenomenon occurs with a Dornier Compact S, a machine distinctly different from the Dornier HM-3. This result also suggests that this phenomenon may be observed generally in SW lithotripters.

Keywords: acute renal injury; extracorporeal shockwave lithotripsy; treatment protocols.

FIG. 1.

Photograph of the treatment head extension fitted to the SW generator of a Dornier Compact S. The extension is black with a white rim at the top (covered by the inflatable shock cushion). This modification allowed proper coupling to the body wall of the pig when the SW focus was in the kidney. SW = shock wave.

FIG. 2.

Bar graph of lesion sizes from the different treatment groups. Pretreatment consisting of 100 low-energy SWs with a 3-minute pause significantly reduced the size of the measured hemorrhagic lesion compared to the group given 2500 SWs with no pretreatment (far left bar). Group sample size is noted next to each of the bars.