Magnetic Resonance Imaging Evaluation of Functional Differences Between In Vivo Human Kidneys and Discarded Human Kidneys During Ex Vivo Normothermic Machine Perfusion

BACKGROUND: With increasing interest in renal normothermic machine perfusion (NMP), a deeper understanding of ex vivo renal physiology is essential to establish NMP as a robust pre-transplant assessment platform. This study utilized magnetic resonance imaging (MRI) to compare in vivo renal physiology in healthy volunteers with ex vivo renal function of human donor kidneys during NMP. METHODS: Multiparametric MRI maps assessing water diffusion, oxygenation, tissue characteristics, and perfusion were obtained from 11 healthy volunteers to define an in vivo renal reference frame. For ex vivo evaluation, 25 discarded human donor kidneys underwent 4 h of oxygenated hypothermic machine perfusion, followed by 6 h of NMP in an MRI-compatible setup. The kidneys were assessed hourly using comparable MRI modalities as in vivo. RESULTS: Ex vivo renal physiology was substantially different from in vivo physiology in terms of MRI-based diffusion patterns, oxygenation, tissue characteristics, and tissue perfusion. Most MRI measurements did not correlate well with conventional parameters such as flow, renal function, and injury markers during NMP. CONCLUSIONS: Our findings highlight distinct differences between in vivo and ex vivo MRI-based renal characteristics in a human cohort, suggesting that parameters beyond conventional in vivo functional markers may warrant consideration when evaluating organ viability during NMP.