Dynamic evaluation of renal resistive index in normoalbuminuric patients with newly diagnosed hypertension or type 2 diabetes

Abstract

Aim/hypothesis Renal resistive index is a useful measure for quantifying alterations in renal blood flow. In the present study we evaluated resistive index at baseline and after vasodilation induced by nitroglycerine in normoalbuminuric patients with type 2 diabetes or essential hypertension, relating the values to indices of systemic vascular dysfunction. Methods Newly diagnosed treatment-naïve type 2 diabetic (n=32) and hypertensive patients (n=49) were compared with 27 age-and sex-matched healthy controls. Renal resistive index was obtained by duplex ultrasound at baseline and after 25 μg sublingual nitroglycerine. Endothelium-dependent (flow-mediated dilation) and -independent (response to nitroglycerine) vasodilation in the brachial artery was assessed by computerised edge detection system. Carotid-femoral pulse-wave velocity and augmentation index were assessed by applanation tonometry. Nitrotyrosine levels, an index of oxidative stress, were also measured. Results Resistive index was higher in diabetic than in hypertensive patients and controls (p < 0.001), while changes in resistive index induced by nitroglycerine were lower in hypertensive patients compared with controls (p< 0.01), and were further reduced in type 2 diabetic patients. Hypertensive and diabetic patients showed significantly increased arterial stiffness, nitrotyrosine levels and reduced endothelial function than controls (p<0.05). Changes in resistive index induced by nitroglycerine were independently related to serum glucose, reactive hyperaemia and aortic pulse-wave velocity in the overall population. Conclusions/interpretation These results support the dynamic evaluation of renal resistive index as an early detector of renal vascular alterations in the presence of type 2 diabetes and hypertension, even before the onset of microalbuminuria.

Doppler ultrasound in kidney diseases: a key parameter in clinical long-term follow-up

“…Bruno et al [6] evaluated RRI among 32 type 2 diabetic patients without micro-albuminuria, hypertension, glucoselowering medications and reduced renal function (GFR \60 mL/min 1.73 m 2 ) and compared results with hypertensive and controls patients. RRI measurements were obtained at baseline and 5 min after pharmacological sublingual administration of 25 lg of glyceryltrinitrate (Dynamic Resistive Index, DRI).…”

New approaches for the evaluation of renal vascular function in diabetes

“…Both studies demonstrate changes in renal blood vessel function independent of increases in albuminuria. However, small increases in ACR were already evident in the 'normoalbuminuric' individuals studied by Bruno et al [7].…”

“…This method has previously been used to assess intra-renal blood changes induced by the administration of renin-angiotensin system blocking agents [6]. However, in this instance, intrarenal RI was assessed by Bruno et al [7] before and after administration of sublingual glyceryl trinitrate. In the second…”

“…This method has previously been used to assess intra-renal blood changes induced by the administration of renin-angiotensin system blocking agents [6]. However, in this instance, intrarenal RI was assessed by Bruno et al [7] before and after administration of sublingual glyceryl trinitrate. In the second study, by Thelwall et al [8], MRI was used to assess total renal blood flow in relation to mean arterial pressure, thereby enabling direct measurement of overall renal RI.…”

“…The study by Bruno et al [7] involved 27 control participants, 49 participants with essential hypertension, and 32 participants with type 2 diabetes and normoalbuminuria. Ages were 51, 52 and 53 years and estimated GFRs were 89, 92 and 87 ml min −1 1.73 m −2 in the three study groups, respectively.…”