Assessment of focal renal ischemia-reperfusion injury in a porcine model using hyperpolarized [1-13C]pyruvate MRI

PurposeIschemic injury in the kidney is a common pathophysiological event associated with both acute kidney injury and chronic kidney disease; however, regional ischemia-reperfusion as seen in thromboembolic renal disease is often undetectable and thus subclinical. Here, we assessed the metabolic alterations following subclinical focal ischemia-reperfusion injury with hyperpolarized [1-C-13]pyruvate MRI in a porcine model. MethodsFive pigs were subjected to 60 min of focal kidney ischemia. After 90 min of reperfusion, a multiparametric proton MRI protocol was performed on a clinical 3T scanner system. Metabolism was evaluated using C-13 MRI following infusion of hyperpolarized [1-C-13]pyruvate. Ratios of pyruvate to its detectable metabolites (lactate, bicarbonate, and alanine) were used to quantify metabolism. ResultsThe focal ischemia-reperfusion injury resulted in injured areas with a mean size of 0.971 cm(3) (+/- 1.019). Compared with the contralateral kidney, the injured areas demonstrated restricted diffusion (1269 +/- 83.59 x 10(-6) mm(2)/s vs. 1530 +/- 52.73 x 10(-6) mm(2)/s; p = 0.006) and decreased perfusion (158.8 +/- 29.4 mL/100 mL/min vs. 274 +/- 63.1 mL/100 mL/min; p = 0.014). In the metabolic assessment, the injured areas displayed increased lactate/pyruvate ratios compared with the entire ipsilateral and the contralateral kidney (0.35 +/- 0.13 vs. 0.27 +/- 0.1 vs. 0.25 +/- 0.1; p = 0.0086). Alanine/pyruvate ratio was unaltered, and we were unable to quantify bicarbonate due to low signal. ConclusionMRI with hyperpolarized [1-C-13]pyruvate in a clinical setup is capable of detecting the acute, subtle, focal metabolic changes following ischemia. This may prove to be a valuable future addition to the renal MRI suite.

Automated summary

This study assessed the metabolic alterations following subclinical focal ischemia-reperfusion injury with hyperpolarized [1-C-13]pyruvate MRI in a porcine model. The results showed restricted diffusion and decreased perfusion in the injured areas compared to the contralateral kidney. The metabolic assessment revealed an increased lactate/pyruvate ratio in the injured areas.