Quantitative assessment of renal structural and functional changes in chronic kidney disease using multi-parametric magnetic resonance imaging

Background. Multi-parametric magnetic resonance imaging (MRI) provides the potential for a more comprehensive noninvasive assessment of organ structure and function than individual MRI measures, but has not previously been comprehensively evaluated in chronic kidney disease (CKD). Methods. We performed multi-parametric renal MRI in persons with CKD (n = 22, 61 +/- 24 years) who had a renal biopsy and measured glomerular filtration rate (mGFR), and matched healthy volunteers (HV) (n = 22, 61 +/- 25 years). Longitudinal relaxation time (T-1), diffusion-weighted imaging, renal blood flow (phase contrast MRI), cortical perfusion (arterial spin labelling) and blood-oxygen-level-dependent relaxation rate (R-2*) were evaluated. Results. MRI evidenced excellent reproducibility in CKD (coefficient of variation <10%). Significant differences between CKD and HVs included cortical and corticomedullary difference (CMD) in T-1, cortical and medullary apparent diffusion coefficient (ADC), renal artery blood flow and cortical perfusion. MRI measures correlated with kidney function in a combined CKD and HV analysis: estimated GFR correlated with cortical T-1 (r = -0.68), T-1 CMD (r = -0.62), cortical (r = 0.54) and medullary ADC (r = 0.49), renal artery flow (r = 0.78) and cortical perfusion (r= -0.81); log urine protein to creatinine ratio (UPCR) correlated with cortical T-1 (r = 0.61), T-1 CMD (r= 0.61), cortical (r = -0.45) and medullary ADC (r = -0.49), renal artery flow (r = -0.72) and cortical perfusion (r =-0.58). MRI measures (cortical T-1 and ADC, T-1 and ADC CMD, cortical perfusion) differed between low/high interstitial fibrosis groups at 30-40% fibrosis threshold. Conclusion. Comprehensive multi-parametric MRI is reproducible and correlates well with available measures of renal function and pathology. Larger longitudinal studies are warranted to evaluate its potential to stratify prognosis and response to therapy in CKD.