Doppler sonography is a noninvasive imaging method, using Doppler parameters of peak systolic velocity (PSV), end diastolic velocity (EDV), and resistive index (RI) to quantify the speed of flow (cm/s) within vessels and the vascular resistance of the organ. Although hydration status is known to affect renogram patterns in normal adults, 7 there is not yet a method to evaluate the effect of hydration on kidney hemodynamics without the use of tracers or contrast agents. 6 However, imaging methods like renal scintigraphy, contrast CT, MRI, and renal angiography are invasive due to the requirements of intravascular injection of radiotracers or contrast agents in order to evaluate dynamic function. 5 Therefore, it is important to understand the role of hydration in the examination of kidney vasculature.Ĭurrently, clinical diagnosis of renal conditions largely relies on physiologic and biochemical markers, radiography, computed tomography (CT), magnetic resonance imaging (MRI), and ultrasonagraphy. 4 Furthermore, hypohydration (loss of fluid ∼2% of body mass) induced by moderate exercise and water restriction may impair endothelial function in healthy adults. 1, 3- 5 Modification of fluid intake as a therapeutic intervention in chronic kidney disease is beneficial in preserving renal function, 1 and hydration decreases the burden of urine production when the kidney is stressed with hypoxia. 2- 4 The effects of hydration and fluid intake adjustment have been reported for both healthy and disease states. 1, 2 It is well established that hydration is a behavioral adaption involved in the maintenance of circulating volume, and that the kidney is the end-organ that responds to changes in body fluid volume by modifying water excretion and conservation. Doppler flow velocities of renal arteries can be considered as noninvasive quantitative markers for evaluating the response of kidney hemodynamics to hydration.Ĭontrol of water homeostasis by the kidney is an important mechanism in the regulation of body fluid volume. The normal kidney reflects proportional increases in PSV and EDV at the main renal artery and interlobar arteries, while maintaining vascular resistance. Our results suggest that Doppler sonography is able to demonstrate changes in kidney hemodynamics within 1 hour after hydration. ICC for intraobserver repeatability in performing kidney Doppler sonography was 0.92. PCC for the correlation of the increase in PSV to the increase in EDV was greater than 0.80. Statistical analyses revealed that the differences in PSV and EDV values before and after hydration at the main renal artery and interlobar arteries of the kidney were significant ( P.05). We tested differences in Doppler parameters before and after hydration using a paired t test, analyzed the correlation of the increase in PSV to the increase in EDV after hydration using Pearson correlation coefficient (PCC), and examined intraobserver reliability using intraclass correlation coefficient (ICC). Quantitative ultrasound Doppler parameters of peak systolic velocity (PSV), end diastolic velocity (EDV), and resistive index (RI) of the main renal artery and the intrarenal (interlobar) arteries were measured immediately before and 1 hour after ingestion of 500 mL of water. MethodsĪ total of 60 native kidneys in 30 normal adult participants (mean age, 26 years) were assessed using Doppler sonography. To examine differences in arterial Doppler velocities of normal adult kidney before and after hydration. However, the effect of hydration on kidney hemodynamics has not been explored via Doppler sonography. Doppler sonography is a noninvasive method to evaluate the hemodynamic status of the kidney, and its parameters are used as direct and indirect predictors of certain parenchyma and renovascular diseases.
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