Can Hyperpolarized (13)C-Urea be Used to Assess Glomerular Filtration Rate? A Retrospective Study

This study investigated a simple method for calculating the single-kidney glomerular filtration rate (GFR) using dynamic hyperpolarized (13)C-urea magnetic resonance (MR) renography. A retrospective data analysis was applied to renal hyperpolarized (13)C-urea MR data acquired from control rats, prediabetic nephropathy rats, and rats in which 1 kidney was subjected to ischemia-reperfusion. Renal blood flow was determined by the model-free bolus differentiation method, GFR was determined using the Baumann–Rudin model method. Reference single-kidney and total GFRs were measured by plasma creatinine content and compared to (1)H dynamic contrast-enhanced estimated GFR and fluorescein isothiocyanate-inulin clearance GFR estimation. In healthy and prediabetic nephropathy rats, single-kidney hyperpolarized (13)C-urea GFR was estimated to be 2.5 ± 0.7 mL/min in good agreement with both gold-standard inulin clearance GFR (2.7 ± 1.2 ml/min) and (1)H dynamic contrast-enhanced estimated GFR (1.8 ± 0.8 mL/min), as well as plasma creatinine measurements and literature findings. Following ischemia-reperfusion, hyperpolarized (13)C-urea revealed a significant reduction in single-kidney GFR of 57% compared with the contralateral kidney. Hyperpolarized (13)C MR could be a promising tool for accurate determination of GFR. The model-free renal blood flow and arterial input function-insensitive GFR estimations are simple to implement and warrant further translational adaptation.