Normothermic machine perfusion (NMP) is increasingly considered for pretransplant kidney quality assessment. However, fundamental questions about differences between in vivo and ex vivo renal function, as well as the impact of ischemic injury on ex vivo physiology, remain unanswered. This study utilized magnetic resonance imaging (MRI), alongside conventional parameters to explore differences between in vivo and ex vivo renal function and the impact of warm ischemia on a kidney’s behavior ex vivo. Renal MRI scans and samples were obtained from living pigs (n = 30) in vivo. Next, kidney pairs were procured and exposed to minimal, or 75 minutes of warm ischemia, followed by 6 hours of hypothermic machine perfusion. Both kidneys simultaneously underwent 6-hour ex vivo perfusion in MRI-compatible NMP circuits to obtain multiparametric MRI data. Ischemically injured ex vivo kidneys showed a significantly altered regional blood flow distribution compared to in vivo and minimally damaged organs. Both ex vivo groups showed diffusion restriction relative to in vivo. Our findings underscore the differences between in vivo and ex vivo MRI-based renal characteristics. Therefore, when assessing organ viability during NMP, it should be considered to incorporate parameters beyond the conventional functional markers that are common in vivo.

中文翻译：

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磁共振成像作为体内和离体常温机器灌注期间肾脏功能差异常规评估的无创辅助手段

常温机器灌注（NMP）越来越多地被考虑用于移植前肾脏质量评估。然而，关于体内和离体肾功能之间的差异以及缺血性损伤对离体生理学影响的基本问题仍未得到解答。这项研究利用磁共振成像（MRI）以及常规参数来探索体内和离体肾功能之间的差异以及热缺血对肾脏离体行为的影响。肾脏 MRI 扫描和样本取自活猪 (n = 30) 体内。接下来，获取肾对并暴露于最小的或 75 分钟的热缺血，然后进行 6 小时的低温机器灌注。两个肾脏同时在 MRI 兼容的 NMP 回路中进行 6 小时的离体灌注，以获得多参数 MRI 数据。与体内和轻微受损的器官相比，缺血性损伤的离体肾脏显示出显着改变的局部血流分布。两个离体组均表现出相对于体内的扩散限制。我们的研究结果强调了基于体内和离体 MRI 的肾脏特征之间的差异。因此，在 NMP 期间评估器官活力时，应考虑纳入体内常见的常规功能标记之外的参数。