BACKGROUND: Although numerous techniques exist for renal blood flow (RBF) estimation, none of the methods have been implemented in routine clinical practice due to their inadequacies and burdensomeness. Previously, we evaluated rubidium-82 ( METHODS: Ten subjects with essential hypertension underwent two treatment periods, receiving spironolactone and placebo in random order. At the end of each period, each subject completed a CONCLUSION: The correlation between