Morphologic Renal Changes Following Piezoelectric Lithotripsy or Spark-Gap Lithotripsy

Abstract

Morphologic changes of the kidney following extracorporeal shock wave lithotripsy (ESWL^†) have been demonstrated by magnetic resonance imaging (MRI) to be present in as many as 85% of patients treated with first-generation electrohydraulic lithotripters. In this study the renal morphologic changes produced by a second-generation piezoelectric machine (Wolf Piezolith 2300) were compared to those of an electrohydraulic lithotripter (Dornier HM3). The mean stone size was 11 mm, and the mean number of shock waves on the Wolf lithotripter was 3,900 at an average power intensity of 900 bar and on the Dornier device was 1,760 shock waves at 21 kV. All patients were studied with renal MRI scans 24 hours following lithotripsy. A subsequent MRI scan was performed at two weeks and then at one month if any changes were noted on the prior study.

Only one of 20 patients (5%) treated on the Wolf Piezolith 2300 showed any changes on MRI. A small perinephric fluid collection noted in this patient was resolved spontaneously by two weeks. In contrast, two of four patients (50%) treated on the Dornier HM3 showed renal changes by MRI, including subcapsular fluid collections and loss of corticomedullary demarcation. This study suggests that piezoelectric lithotripsy may be less damaging to the renal parenchyma and surrounding tissues than electrohydraulic shock wave lithotripsy. The significantly reduced incidence of acute morphologic alterations noted on post-lithotripsy MRI scans supports this conclusion.

Supported by USPHS Training Grant #5T32-DK07307.