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

Abstract

Doppler ultrasound has been extensively used in detecting reno-vascular diseases, showing to be a non-invasive, safe, low cost and repeatable tool. The Renal Resistive Index (RRI) [(peak systolic velocity - end diastolic velocity)/peak systolic velocity] is a semi-quantitative index derived by Doppler evaluation of renal vascular bed. Normally RRI is in the range of 0.47-0.70, it increases with aging and, usually, it shows a difference between the two kidneys less than 5-8 %. RRI is an important prognostic marker in chronic kidney diseases (CKD), both in diabetic and non-diabetic kidney diseases, because, in longitudinal prospective studies, it significantly correlated with hemodynamic (ABPM, SBP, DBP, pulse pressure) and histopathological parameters (glomerular sclerosis, arteriolosclerosis, interstitial fibrosis/tubular atrophy, interstitial infiltration). In acute kidney injury (AKI) RI is a valid tool in differentiating between pre-renal and renal failure and in predicting renal response to vaso-active agents. In addition a RRI >0.74 can predict the onset of AKI in septic patients. Renal Resistive Index is a useful marker in allograft diseases because it has been widely showed a correlation with histological lesions during worsening of renal function, both in acute rejection and in chronic allograft nephropathy. Recent studies suggest its role in the risk of new onset diabetes after transplantation and it could be one of the parameters to evaluate to shift or withdrawal immunological and/or hypertensive therapy.

Keywords: Acute kidney injury; Chronic kidney disease; Diabetic nephropathy; Renal resistive index; Renal transplantation.

Conflict of interest statement

Compliance with ethical standards Conflict of interests The authors declare that they have no competing or conflicting interests. Informed consent For this type of study formal consent is not required. Human and animal studies The study described in this article does not contain studies with animal and human subjects performed by any of the authors.

Figures

Fig. 1

The Doppler Renal Resistive Index, labeled as IR in the figure, is equal to the ratio of the difference between peak systolic velocity (PSV) and enddiastolic velocity (EDV) divided by PSV, obtained from the doppler spectrum of intrarenal segmental and interlobar arteries