A previous study by Radermacher et al suggested that the presence of irreversible renal microvascular changes, e.g. nephroangiosclerosis, could prevent the patients from having benefit with revascularization. In fact an intrarenal resistance index (RI) > 0.80 at the Doppler analysis was claimed to predict no improvement of BP or renal function, as assessed by measuring the creatinine clearance. However, the latter is an index of global function, and therefore provides no information on the GFR of the ischemic kidney.