CT-based Automated Volumetry as a Biomarker of Global and Split Renal Function in Living Kidney Donors

Abstract Background Kidney volumetry derived from CT has been proposed as a surrogate of renal function in living kidney donor evaluation. However, clinical integration has been limited by reader-dependent workflows and semiautomatic methods susceptible to image quality. Purpose To evaluate whether fully automated CT-based segmentation of renal cortex, medulla and total parenchymal volume provides reproducible volumetric biomarkers associated with global and split renal function in living kidney donor candidates. Materials and Methods In this retrospective single-center study, 461 living kidney donor candidates (2003–2021) underwent contrast-enhanced abdominal CT. A convolutional neural network was trained to automatically segment cortical, medullary, and total parenchymal volumes on arterial-phase images. Segmentation performance was evaluated against manual reference annotations. Volumes were indexed to body surface area. Associations with eGFR, 24-hour creatinine clearance, cystatin C, and tubular clearance were assessed using Spearman correlation coefficient (ρ), and side-specific volume fractions were compared with scintigraphy -derived split function. Results Automated segmentation achieved excellent agreement with expert reference segmentations (Dice 0.95 for cortex; 0.90 for medulla). eGFR correlated moderately with cortical (ρ = 0.46) and total parenchymal volume (ρ = 0.45), and modestly with medullary volume (ρ = 0.30). Similar associations were observed for other global measures, with the strongest correlation for cortical volume and tubular clearance (ρ = 0.53). Side-specific volume fractions correlated with scintigraphy-derived split renal function (ρ = 0.49–0.56; all p < 0.001). Conclusion Automated CT-based renal subcompartment segmentation provides reproducible volumetric biomarkers within routine donor evaluation. Cortical volume performs comparably to total parenchymal volume and tracks split renal function at the cohort level, suggesting potential utility in donor assessment.