Ultrasound Doppler renal resistive index: a useful tool for the management of the hypertensive patient

Abstract

The Doppler-derived renal resistive index has been used for years in a variety of clinical settings such as the assessment of chronic renal allograft rejection, detection and management of renal artery stenosis, evaluation of progression risk in chronic kidney disease, differential diagnosis in acute and chronic obstructive renal disease, and more recently as a predictor of renal and global outcome in the critically ill patient. More recently, evidence has been accumulating showing that an increased renal resistive index not only reflects changes in intrarenal perfusion but is also related to systemic hemodynamics and the presence of subclinical atherosclerosis, and may thus provide useful prognostic information in patients with primary hypertension. On the basis of these results, the evaluation of renal resistive index has been proposed in the assessment and management of patients with primary hypertension to complement other signs of renal abnormalities.

FIGURE 1

Renal RI measurement technique. A sample volume (arrow) is placed within an intrarenal artery (an arcuate or interlobar one) under Color Doppler guidance and spectral analysis of vascular signals is obtained. The measurement calipers are then set at the systolic peak (white open arrow) and end diastole (black open arrow) of a waveform, and the RI is calculated according to the formula (PSV-EDV)/PSV. EDV, end diastolic velocity; RI, resistive index; SV, peak systolic velocity.

FIGURE 2

Renal resistive index and target organ damage in primary hypertension. IMT, intima–media thickness; LVH, left ventricular hypertrophy; PH, primary hypertension; TOD, indicates target organ damage .

FIGURE 3

Renal resistive index and cardiovascular and renal outcomes in primary hypertension. Low and high resistive index were defined on the basis of sex-specific median values of RI (i.e. 0.62 for men and 0.67 for women in the group with GFR ≥60 ml/min; 0.73 for men and 0.72 for women in the group with GFR <60 ml/min). CIs, confidence intervals; HRs, indicates hazard ratios; GFR, estimated glomerular filtration rate; RI, resistive index .