Focused destruction of renal tissue by a narrow focal width lithotripter.

Abstract

Although lithotripters can differ substantially in acoustic output, renal response to SWs has been thoroughly characterized for only one type of lithotripter (moderate-pressure ∼40 MPa, intermediate-focal-width 8–9 mm, Dornier-HM3). Therefore, we assessed injury using a high-pressure (∼85 MPa), narrow-focal-width (3–4 mm) device (Storz-SLX). SWs were administered to the lower renal pole of pigs (15 kg) (PL-9, 2000 or 4000 SWs at 120 SWs/min; or 2000SWs at 60 SW/min) followed by serial sectioning to quantify lesion. Tissue damage with the SLX showed an abrupt transition between injured and unaffected tissue. Core of lesion was typically devoid of recognizable structure, with renal tubules, glomeruli, vessels essentially eliminated. The lesion extended from cortex to medulla, and in some kidneys homogenized tissue could be tracked across full thickness of the kidney. In comparison, the lesion using HM3 was not as severe with only focal spots of hemorrhage and no areas of complete tissue destruction. Doubling the SW-dose with SLX did not increase lesion volume as occurred with HM3. Also, slowing the SW-rate of the SLX to 60 SW/min did not have a protective effect as observed with other lithotripters. These findings suggest that lithotripters having different acoustic characteristics are capable of producing different forms of tissue damage. [Work supported by NIH-DK43881.]