Morphologic changes of the kidney after extracorporeal shock wave lithotripsy (SWL) have been demonstrated by magnetic resonance imaging (MRI) to be present in as many as 85% of patients treated with first-generation electrohydraulic lithotripters. We compared the acute renal morphologic changes produced by a second-generation piezoelectric machine (Wolf Piezolith 2300) with those of an electrohydraulic lithotripter (Dornier HM3). All patients were studied with renal MRI scans 24 hours after lithotripsy and then serially with repeat MRI scans at 2 weeks and at 1 month if any changes were noted on the prior study. Only 1 of 20 (5 %) of patients treated on the Wolf Piezolith 2300 showed any changes by MRI, the change consisting of localized perinephric edema present on the scan at 24 hours that resolved spontaneously by 2 weeks. In contrast, 2 of 4 of the patients treated on a Dornier HM3 showed specific renal changes, including subcapsular fluid collections and loss of corticomedullary demarcation, and all 4 had acutely increased renal volume on the treated side. These findings suggest that piezoelectric lithotripsy may be less damaging acutely to the renal parenchyma and surrounding tissues than electrohydraulic machines.
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