Kidney Structure and Blood Flow Predict Function and Enable Image-Based eGFR With Non-Contrast MRI

Determine whether non-contrast MRI metrics of kidney structure and hemodynamics predict glomerular filtration rate (GFR). Develop and prospectively validate an image-based estimated GFR (eGFR) approach that is free of radiation and serum biomarkers. Eighty-nine healthy adults without known kidney disease underwent a 3 T MRI exam, including T1-weighted anatomical imaging, phase contrast MRI for renal blood flow (RBF), and T2* mapping. Seventy-four participants comprised a model development cohort and 20 served as a prospective validation cohort. Serum creatinine-based eGFR was used as the reference standard. Bivariate and multivariate linear regression identified imaging predictors of eGFR and was used prospectively to generate image-based eGFR models. Models were evaluated with bootstrapping and prospectively validated using bias, root means squared error, and p30/p20/p10 accuracy metrics. Age-related trajectories of imaging parameters were also assessed. On bivariate analysis, cortical thickness (r² = 0.38), RBF (r² = 0.29), total kidney volume, cortical R2*, and medullary R2* were significantly associated with eGFR (all p < 0.05). In multivariate analysis, only cortical thickness and RBF remained statistically significant (r² = 0.47, p < 0.001). When used prospectively, the image-based eGFR models including cortical thickness and/or RBF demonstrated a low bias (-4.9 to 3.4 mL/min/1.73 m²) and acceptable accuracy (p30 ≈87%-92%) in both bootstrapped testing and prospective validation. In our healthy cohort, age was the strongest determinant of eGFR, RBF, and cortical thickness, with similar age-related declines in eGFR (-8.0%/decade) and RBF (-7.8%/decade). Non-contrast MRI measures of renal cortical thickness and blood flow are strong, complementary predictors of kidney function. An image-based eGFR model achieved bias and accuracy comparable to serum creatinine-based equations in healthy adults. This proof-of-concept supports the feasibility of a safe, contrast-free, and physiology-informed approach to estimating GFR and motivates further validation against measured GFR and in broader clinical populations.