Ex Vivo Analysis of Kidney Graft Viability Using 31P Magnetic Resonance Imaging Spectroscopy.

BACKGROUND The lack of organs for kidney transplantation is a growing concern. Expansion in organ supply has been proposed through the use of organs after circulatory death (DCD). However, many DCD grafts are discarded due to long warm ischemia times, and the absence of reliable measure of kidney viability. P MRI spectroscopy (pMRI) is a noninvasive method to detect high-energy phosphate metabolites, such as adenosine triphosphate (ATP). Thus, pMRI could predict kidney energy state, and its viability prior to transplantation. METHODS To mimic donation after circulatory death (DCD), pig kidneys underwent 0, 30 or 60 minutes of warm ischemia, prior to hypothermic machine perfusion. During the ex vivo perfusion, we assessed energy metabolites using pMRI. In addition, we performed Gadolinum (Gd) perfusion sequences. Each sample underwent histopathological analyzing and scoring. Energy status, and kidney perfusion were correlated with kidney injury. RESULTS Using pMRI, we found that in pig kidney, ATP was rapidly generated in presence of oxygen (100kPa), which remained stable up to 22hrs. Warm ischemia (30 and 60 minutes) induced significant histological damages, delayed cortical and medullary Gd elimination (perfusion), and reduced ATP levels, but not its precursors (AMP). Finally, ATP levels, and kidney perfusion both inversely correlated with the severity of kidney histological injury. CONCLUSIONS ATP levels, and kidney perfusion measurements using pMRI, are biomarkers of kidney injury after warm ischemia. Future work will define the role of pMRI in predicting kidney graft, and patient's survival.