Effect of Sodium Depletion on Renin Activity of Renal Venous Plasma in Renovascular Hypertension

In a patient with renovascular hypertension, renal venous renin-activity determinations were carried out during normal sodium intake, after sodium depletion, and after sodium repletion. When the patient was eating a normal sodium diet, renal venous renin-activity levels failed to lateralize, a finding consistent with the results of isotope renography and two separated renal function studies. However, renal venous renin-activity ratios lateralized (ratios greater than 2:1) to the affected side when the patient's severe sodium depletion lasted for three days. From this finding, it was correctly predicted that relief of hypertension would follow nephrectomy for complete occlusion of a branch artery secondary to fibromuscular dysplasia. Acute sodium depletion increases the diagnostic sensitivity of renal venous renin-activity testing in the determination of functional significance of renovascular lesions in hypertensive patients.