The incidence of renal cell carcinomas (RCCs) has increased significantly over time due to the widespread use of cross-sectional imaging with incidental cancer detection. RCCs vary widely in histological grade and risk of metastasis. However, current imaging techniques cannot reliably differentiate low grade, indolent RCCs from localized but potentially aggressive RCCs, resulting in the over-treatment of many indolent cancers. Increasing evidence has shown that increased glycolysis with lactate production is a dominant metabolic feature of RCCs. In particular, lactate dehydrogenase expression is positively correlated with RCC grade, and a strong predictor of tumor progression and poor prognosis. Hyperpolarized 13C MR allows real time investigation of cellular metabolism, and provides time-resolved metabolic kinetics that reflects flux through enzyme-catalyzed reactions. The purpose of this study is to investigate whether hypeprolarized 13C pyruvate MR can inform on the LDH activity in orthotopic RCC tumor models.