The long-term effects of extracorporeal shockwave lithotripsy (SWL) on children are unclear. At 40 days of age, with an average weight of 166 g, 34 Wistar white rats were divided into three groups: 9 rats (control group) received no shockwaves, 10 rats (Group 1) received 1000 shockwaves at 16.0 kV, and 15 animals (Group 2) received 1000 shockwaves at 17.2 kV. Six months later, at maturity, body weight; lithium and creatinine; fractional sodium, potassium, and lithium excretion; and the clearances of lithium and creatinine were measured, and the kidneys were studied grossly and histologically. We found no significant changes in overall animal or renal growth between the post-SWL groups and the control group. However, there were significant changes in renal function, mainly in Group 2; the animals of this group presented a significant increase in blood lithium and potassium, besides a significant decrease in the fractional potassium excretion compared with the control group. Furthermore, the animals in Group 2 showed permanent histologic renal changes, including red cells in Bowman's capsule and glomerular congestion. The disorders caused by SWL are compatible with hyporeninemic hypoaldosteronism, an inappropriate low plasma renin activity and aldosterone deficiency. We conclude that SWL does not affect either overall animal or renal growth but may cause permanent histologic damage and significant changes in renal function.8191-4