Doppler evaluation of renal resistivity index in healthy conscious horses and donkeys.

Francesca Freccero,Mario Cipone,Marina Petrucelli,Micaela Sgorbini,Irene Nocera,Shigehiko Ogoh

doi:10.1371/journal.pone.0228741

Abstract

The renal resistive index (RRI) is used as a measurement of downstream resistance in arteries. The aim of this study was to assess the RRI of the arcuate arteries by pulsed-wave Doppler ultrasonography in healthy conscious horses and donkeys, and to verify any differences related to age, breed, bodyweight (BW) or body condition (BCS). Thirty-three healthy conscious horses and nine donkeys had their systolic and diastolic flow velocities at the level of the arcuate arteries estimated by pulsed-wave Doppler ultrasound, and the RRI was calculated. The relationship of RRI with age, breed (Trotters vs. other breeds), bodyweight (BW), and body condition score (BCS) were evaluated. PW Doppler evaluation of RRI was successfully applied in most of the horses, but to date not in the donkeys. In horses, median RRI values for the right kidney (0.58±0.006) were statistically higher than for the left (0.51±0.006). For the donkeys the values were comparable. There was no significant difference in RRI between horses younger or older than 15 years, and between breeds in horses. No correlation with age, BW or BCS was found in either horses or donkeys.

Highlights

In human medicine, it has been long considered a good tool to evaluate renal microcirculation in both physiological and pathological conditions [1], by means of investigating arterial compliance and/or resistance [2]
renal resistive index (RRI) is affected by a complex interplay of renal and extra-renal factors
The interpretation of RRI as solely reflective of renal vascular resistance has to be made in consideration of the systemic hemodynamic and cardiovascular status [1]

Summary

Introduction

It has been long considered a good tool to evaluate renal microcirculation in both physiological and pathological conditions [1], by means of investigating arterial compliance and/or resistance [2]. The interpretation of RRI as solely reflective of renal vascular resistance has to be made in consideration of the systemic hemodynamic and cardiovascular status [1]. When vascular resistance increases due to obstruction or vasoconstriction, diastolic blood flow slows down with respect to systolic blood [3]. This produces a higher decrease in end-diastolic velocity rather than in peak systolic velocity and, increases RRI [4]. Using the RRI to assess the resistance at distal arterial branches (arcuate or interlobar) reveals the degree of intrarenal damage and can be used to evaluate renal transplants in humans [5] and small animals [6,7,8]

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