Evaluation of Multimodal MRI Diffusion and Multiphase CT Parameters for Estimating Glomerular Filtration Rate in...

This exploratory study aims to develop a multimodal model predicting estimated glomerular filtration rate (eGFR) by integrating functional Magnetic Resonance Imaging (MRI) diffusion metrics and multiphase Computed Tomography (CT) hemodynamic indices in acute urinary obstruction.

Thirty-five patients with acute urinary obstruction underwent multiphase CT and Diffusion-Weighted Imaging (DWI). We measured DWI-based indices-including Apparent Diffusion Coefficient (ADC), Slow Diffusion Coefficient (SDC), and normalized ratios-alongside CT-derived metrics, specifically Difference of Renal Attenuation (DRA), Corticomedullary Differentiation (CMD), and Difference in Corticomedullary Differentiation (DCMD). These indices were compared between obstructed and contralateral (normal) kidneys to assess diagnostic value Predictive models for eGFR were developed using various index combinations, selecting the optimal model based on the highest Adjusted R-squared (R²). Model accuracy was validated using Mean Absolute Error (MAE) and Root Mean Square Error (RMSE), with age and sex as fixed covariates (p<0.05).

Obstructed kidneys exhibited significantly lower native CT density (32.5 ± 4.2 vs 34.3 ± 2.6 HU, p= 0.011) and reduced CMD (p< 0.001) than normal kidneys. Although ADC and ADC ratios showed no significant differences (p> 0.05), the SDC and SDC ratios (rSDC) were significantly higher in obstructed kidneys (SDC: 0.14 ± 0.03 vs 0.13 ± 0.03; rSDC_Muscle: 7.05 ± 2.69 vs 6.18 ± 2.34; rSDC_Spleen: 1.70 vs 1.47; all p< 0.05). Combining diffusion metrics with multiphase CT attenuation enhanced eGFR prediction. The best model, integrating ADC, CMD, and Mean_rADC_Muscle, achieved an adjusted R²= 0.433 (p= 0.0005). The similar MAE (0.552) and RMSE (0.695) values demonstrate consistent eGFR estimation with minimal variability.

This exploratory investigation highlights the potential of a multimodal framework that integrates CT hemodynamic indices with MRI microstructural metrics for noninvasive eGFR estimation in acute urinary obstruction. This quantitative methodology demonstrates promising capability in identifying localized renal impairment, serving to complement established laboratory diagnostics.