Effect of shock wave exposure during ESWL on renal function

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Many studies have reported the effect of shock wave exposure on the human body during extracorporeal shock wave lithotripsy (ESWL). We studied the effect of high-energy shock waves on the kidney in ex vivo experiments using dogs and in in vivo experiments on patients with kidney stones.ex vivo results : The exposure of high-energy shock waves (17kV, 1mu/sec) decreased renal blood flow rate, which was calculated using the microsphere method and analyzing the initial time-activity curve on 99mTc-DTPA renogram. The renal blood flow rate significantly decreased after more than 500 shots, and the decrease correlated with the increase in the number of shots until 2, 000 shots. Time required to reach the maximum activity (Tmax) and tixne required to reach a half of the maximum activity (T_<1/2>) of excretory phase of DTPA renogram were prolonged significantly. All these changes were observed for 4 weeks after ESWL and were aggravated by repeated sessions of ESWL. Histological studies revealed … More hemorrhage in the parenchyma of the exposed site, especially in the peritubular interstitial tissue, resulting in degeneration of tubular epithelial cell of the exposed site.in vivo results : We measured urine cell-escaped enzyme activities and urine low molecular proteins, such as beta_2-microglobulin and alpha_2-microglobulin, before and after ESWL in patients with kidney stones. We also studied changes in renal function after ESWL in these patients by 99mTc-DrPA renogram. Blood flow of the non-exposed kidney as well as the exposed kidney decreased after ESWL. Hematuria and increased activities of NAG, LDH and gammaGTP were noted immediately after ESWL, but these abnormalities subsided within 4 days. Urine low molecular proteins showed abnormally high levels for more than 4 days after ESWL, suggesting renal tubular dysfunction. These changes were especially significant in patients complicated with urinary infection and obstruction due to steinstrabetae. Repeated sessions of ESWL at intervals of one or two months caused irreversible renal damage in about 10% of the patients, and the degree of the damage correlated with the number of sessions and total shots of shock waves.Conclusion : Shock wave exposure onto the kidney apparently caused tissue damage such as contusion, hemorrhage, ischemia and necrosis, and the degree of the damage correlated with the energy of shock waves and the number of shots. Urinary infection and urinary obstruction are considered risk factors, infection being the most important factor. Sessions of shock wave exposure onto the kidney should be at least 4 weeks apart, minimizing the risks of these factors. Less