Are plasma renin activity and aldosterone levels useful as a screening test to differentiate between unilateral and bilateral renal artery stenosis in hypertensive patients?

Abstract

Objective: To evaluate the serum aldosterone (Ald)/plasmatic renin activity (PRA) ratio as a surrogate marker of renin-angiotensin-aldosterone system status in unilateral (Uni)- and bilateral (Bi)-renal artery stenosis (RAS).

Methods: Seven hundred and eight hypertensive patients (HTP) were studied. Intermediate and high pretest risk of RAS was detected in 66 HTP who subsequently underwent renal gadolinium-enhanced magnetic resonance and arteriography. After application of exclusion criteria 51 HTP remained: 16 with Uni-RAS, 16 with Bi-RAS and 19 essential hypertensives with normal arteries. Nineteen normotensive individuals were also studied. Ald and PRA were determined before and after stenosis resolution by balloon angioplasty and stent implantation.

Results: Ald/PRA (ng/dl per (ng/ml per h(-1))) was markedly high in Bi-RAS (5.92 +/- 2.30, P < 0.001), and markedly low in Uni-RAS (0.38 +/- 0.17, P < 0.001) versus essential hypertensives (1.52 +/- 2.02). Multilevel likelihood ratios for Bi-RAS were positive for Ald/PRA higher than 3.6, negative for Ald/PRA lower than 0.2, and neutral for Ald/PRA at least 0.2 and 3.6 or less. ROC analysis identified Ald/PRA lower than 0.5 and Ald/PRA higher than 3.7 to have the best sensitivity and specificity to detect Uni-RAS and Bi-RAS, respectively. In Uni-RAS, but not in Bi-RAS, postinterventional PRA was significantly lower than basal PRA. In Uni-RAS and Bi-RAS, postinterventional Ald was approximately 30% and approximately three times lower than basal Ald, respectively. In essential hypertensives, PRA and Ald showed no changes in the same period.

Conclusion: In the population studied, Ald, PRA and Ald/PRA were significantly different among essential hypertensives, and HTP with Uni-RAS or Bi-RAS. Studies with a higher number of patients will allow exploration of the usefulness of pharmacologic aldosterone blockade in Bi-RAS, and to assess the relevance of Ald/PRA to differentiate Uni-RAS from Bi-RAS.