Assessment with Unenhanced MRI Techniques of Renal Morphology and Hemodynamic Changes during Acute Kidney Injury and Chronic Kidney Disease in Mice

<b><i>Background/Aims:</i></b> Changes in renal oxygenation and perfusion have been identified as common pathways to the development and progression of renal disease. Recently, the sensitivity of hemodynamic response imaging (HRI) was demonstrated; this is a functional magnetic resonance imaging (MRI) method combined with transient hypercapnia and hyperoxia for the evaluation of renal perfusion and vascular reactivity. The aim of this study was to utilize HRI for the noninvasive evaluation of changes in renal hemodynamics and morphology during acute, chronic and acute-on-chronic renal failures. <b><i>Methods:</i></b> Renal-HRI maps and true fast imaging with steady-state precession (True-FISP) images were used to evaluate renal perfusion, morphology and corticomedullary differentiation (CMD). MR images were acquired on two mouse models of kidney injury: adenine-induced chronic kidney disease (CKD) and rhabdomyolysis-induced acute kidney injury (AKI). Serum urea was measured from these mice in order to determine renal function. <b><i>Results:</i></b> Renal-HRI maps revealed a blunted response to hypercapnia and hyperoxia with evolving kidney dysfunction in both models, reflecting hampered renal vascular reactivity and perfusion. True-FISP images showed a high sensitivity to renal morphological changes, with different patterns characterizing each model. Calculated data obtained from HRI and True-FISP during the evolution of renal failure and upon recovery, with and without protective intervention, closely correlated with the degree of renal impairment. <b><i>Conclusions:</i></b> This study suggests the potential combined usage of two noninvasive MRI methods, HRI and True-FISP, for the assessment of renal dysfunction without the potential risk associated with contrast-agents administration. HRI may also serve as a research tool in experimental settings, revealing the hemodynamic changes associated with kidney dysfunction.