Aldosterone-Renin Ratio and Side-Selective Renal Perfusion in Essential Hypertension

The decrease in kidney perfusion as often observed in hypertensive individuals does not necessarily occur in a symmetrical fashion, thereby potentially introducing left-right differences in response to vasoactive agents. Increased aldosterone levels have been associated with reduced renal perfusion in normotensive and hypertensive individuals, but it is unknown whether both kidneys are equally affected in this respect and how angiotensin II is involved in this relationship. Therefore, our aim was to investigate the association of both aldosterone and the aldosterone-renin ratio with side-selective renal blood flow in essential hypertension. We studied 146 essential hypertensive patients with patent renal arteries who had undergone renal angiography for exclusion of renal artery stenosis. Prior to contrast administration, blood samples were drawn for the determination of renin and aldosterone levels, and side-selective renal blood flow was measured using the (133)Xenon washout technique. Left mean renal blood flow (MRBF) was significantly lower than right MRBF (227 +/- 74 vs. 250 +/- 76mL * min(-1) * 100g kidney(-1), P = 0.01). We could not demonstrate a correlation of ln aldosterone or ln renin with left or right kidney perfusion. Ln aldosterone-renin ratio (ARR), however, was inversely and independently associated with left MRBF (beta = -13.993, P = 0.02; fully adjusted model) but not with right MRBF. A higher ARR corresponds to reduced perfusion of the left kidney, yet is not associated with right kidney perfusion. Especially under circumstances of diminished right renal blood flow, this may affect blood pressure and kidney function.