Magnetic resonance imaging of renal oxygenation.

Renal hypoxia has a key role in the pathophysiology of many kidney diseases. MRI provides surrogate markers of oxygenation, offering a critical opportunity to detect renal hypoxia. However, studies that have assessed the diagnostic performance of oxygenation MRI for kidney disorders have provided inconsistent results because MRI metrics do not fully capture the complexity of renal oxygenation. Most oxygenation MRI studies are descriptive in nature and fail to detail the pathophysiological importance of the imaging findings. These limitations have restricted the clinical application of oxygenation MRI and the full potential of this technology to facilitate early diagnosis, risk prediction and treatment monitoring of kidney disease has not yet been realized. Understanding of the relationship between renal tissue oxygenation and MRI metrics, which is affected by kidney size, tubular volume fraction and renal blood volume fraction, and measurement of these factors using novel MR methods is imperative for correct physiological interpretation of renal MR oximetry findings. Next steps to enable the clinical adoption of MR oximetry should involve multidisciplinary collaboration to address standardization of acquisition and data analysis protocols and establish reference values of MRI metrics.