High Dose Lithotripsy Impairs Kidney Function, Researchers Say
INDIANAPOLIS—The length and severity of kidney function impairment caused by shock wave lithotripsy may be directly linked to the number of shock waves administered for the treatment of kidney stones, researchers at Indiana University School of Medicine reported Sunday, May 31, at the 93rd Annual Meeting of the American Urological Association at San Diego May 30- June 4.
Lynn R. Willis, Ph.D., professor of pharmacology and of medicine at IU School of Medicine, and a team of researchers subjected anesthetized pigs to doses of shock waves to test the safety of exposure. One kidney of each pig received typical lithotripsy treatment in the amount of 2,000 shock waves or an excessive treatment of 8,000 shock waves.
Lithotripsy is used to break up kidney stones and upper ureteral stones in humans. The shock waves break the stones into tiny fragments so they can be excreted in the urine.
Researchers were interested in determining if the severity of changes in kidney function after lithotripsy could be correlated to different doses of shock waves. There are no prior studies testing how the kidney responds to various levels of shock waves in animal models or human patients.
By measuring changes in kidney blood flow and the animals’ ability to make urine, researchers found that 8,000 shock waves applied to one kidney caused similar large and sustained reductions of blood flow and function in both kidneys.
“The data suggest that shock wave lithotripsy releases a substance that reduces blood flow in both kidneys, despite the fact that only one kidney was subjected to the shock waves,” said Dr. Willis. “Further study is warranted to determine why both kidneys are affected.”
Blood flow is critical to healthy kidney function. The study showed that, following high dose shock wave treatment, blood flow to both kidneys was reduced for the four-hour length of the study.
“Blood flow influences filtration, which is the basic function by which kidneys eliminate wastes,” Dr. Willis said. “After 1½ hours of severely reduced blood flow, kidney cells may begin to die. During the four-hour course of this study, there was at least a 50 percent reduction in blood flow and at least a 50 percent drop in urine formation in both kidneys.”
The animals were subjected to either 2,000 or 8,000 shock waves. The 2,000 shock wave level is a typical clinical dose, but higher amounts are administered if treatment indicates.
“All people normally lose kidney cells and function as we age, but because we normally have two kidneys and can manage with only one, age-related losses of kidney function usually pose no significant problems,” Dr. Willis said.
“However, if someone loses a significant number of kidney cells because of high-dose or repeated lithotripsy treatments, those losses in addition to the normal age-related losses of kidney cells may eventually impair the kidneys’ ability to control blood pressure or lead to kidney failure.”
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