Low-Renin Hypertension After Extracorporeal Shock Wave Lithotripsy

To the Editor.—  The process of stone disintegration by extracorporeal shock wave lithotripsy (ESWL) causes multiple hemorrhages in the adjacent renal parenchyma. These hemorrhages may be reabsorbed completely or may heal by scar tissue formation.¹ Such changes cause reduced blood flow to the traumatized kidney in about 25% of patients, detectable immediately² and at 18 months³ after the procedure. As many as 8% of patients may develop a sustained marked increase in blood pressure within a few days to as long as a year after ESWL.³ Because renal trauma is a well-recognized cause of renovascular hypertension and there may be a long interval between renal injury and the onset of hypertension, it is likely that there is a causal relationship between renal trauma caused by ESWL and the subsequent onset of hypertension. Both the hypertension following compression of renal parenchyma by subcapsular hematoma (Page kidney) and