Quantitation of shock wave lithotripsy-induced lesion in small and large pig kidneys

Abstract

Background: Shock wave lithotripsy (SWL) is known to cause injury to the kidney. However, it is not known how lesion size varies as the parameters of SWL treatment (number of shocks, kilovoltage, kidney size) are changed. This hypothesis could not be tested because there was no method available to quantitate accurately the SWL-induced renal lesion. Methods: A dosage of 2,000 shocks at 24 kV delivered by an unmodified Dornier HM3 lithotripter was applied to the lower pole calyx of the right kidney of small and large pig kidneys. A new method was developed to embed a whole pig kidney for serially sectioning, recording, and digitization. Automated computer color recognition made it possible to discriminate regions of hemorrhage from undamaged tissue and allowed quantitation of the lesion in single sections and in the entire kidney. Results: The new protocol resulted in an accurate identification of sites of hemorrhage and calculations of the volume fraction of injured renal tissue. Lesion size induced in small kidneys was significantly larger than that induced in the larger kidneys (7.6 ± 1.2% and 1.6 ± 0.7%, respectively). Conclusions: Computer segmentation of serially sectioned SWL- treated kidneys has determined that kidney size is a risk factor for enhanced renal injury.