Unstimulated renal venous renin ratio predicts improvement in hypertension following nephrectomy for unilateral renal disease.

The ability of renal venous renin ratio (RVRR) to predict the blood pressure response to nephrectomy was studied in 45 hypertensive patients followed for at least 1 year after nephrectomy. Twenty patients had unilateral chronic parenchymal renal disease (UCPR) and 25 patients had unilateral renal artery stenosis (RAS). The RVRR procedure was performed according to a strict protocol which included sodium restricted diet (40 mmol daily) and hospital admission, with one set of unstimulated samples collected after overnight recumbency, and at least one further set collected after sympathetic nervous system stimulation induced by tilting or i.v. diazoxide. In only 3 of 12 patients with serum creatinine 0.15 mmol/l or higher and presumed bilateral renal disease was hypertension improved. If these 12 patients are excluded, RVRR was a good predictor of outcome, but only if the question of unstimulated and stimulated ratios was considered. Whereas inclusion of stimulated ratios increased the predictive accuracy to 81% in RAS, and avoided two false-negatives, in UCPR the stimulated ratio created four false-positives. Since there were no false-negatives and six true-negatives in UCPR, overnight recumbent RVRR was a perfect predictor of outcome in this sub-group. It appears that RVRR without sympathetic stimulation is most reliable in UCPR, and RVRR during sympathetic stimulation in RAS, raising the question that renin regulation may be different in these two conditions.