Renal ischemia-reperfusion injury (IRI) and its clinical manifestation, acute kidney injury (AKI), is a significant source of morbidity in diverse medical and surgical scenarios including septic shock, cardiac arrest, cardiovascular surgery, trauma, and kidney transplantation. IRI involves an initial ischemic insult, ATP depletion, mitochondrial dysfunction and release of calcium, protease complexes and free radicals, followed by reperfusion that activates innate immune pathways, causing cell apoptosis and adaptive immune responses that can be locally destructive [1]. AKI is a costly medical problem (>$10B and >1M patients annually in the US) for which there is no current therapeutic modality [2]. The care of end-stage renal disease, which can result from renal IRI and AKI, is one of the major line items in the US federal health care budget. AKI contributes significantly to hospital stay, morbidity, and mortality [3-7]. Despite the extensive metabolic derangements that accompany renal IRI, there is an absence of experimentally and clinically useful markers to study this process or predict the clinical course following AKI in an expedient manner. Accordingly, we demonstrate here the feasibility of using HP carbon-13 MRI to image metabolic activity in mice recovering from renal IRI.A C57BL/6 mouse was subjected to standardized unilateral warm renal IRI through laparotomy and 28min microvascular clamp of the left renal pedicle under tight temperature control at 37°C [8]. Post-operatively, a venous tail vein catheter was placed and the mouse was placed in a 9.4T vertical-bore (Bruker Inc.) micro-imaging MRI system. The mouse temperature was regulated at 37.0 ± 0.5°C by circulating warm water in the gradient insert and monitored by an internal temperature sensor and a trans-rectal probe. Respiration was monitored using a respiratory cushion. All images were acquired using a 25mm ¹H/¹³C saddle-coil (Bruker Inc.). Proton T₂-weighted images were acquired using a multi-slice RARE sequence (TR/TE = 700/20ms, ETL = 8, NA = 2, 128x128 voxels). 22.5µL of [1-¹³C]-pyruvate (Cambridge Isotopes Inc.) was polarized using a HyperSense DNP polarizer (Oxford Instruments) to over 15%. The sample was melted with 4mL of a dissolution buffer (40mM Trizma, 80mM NaOH, 50mM NaCl, 0.1g/L EDTA) at 180°C to yield an isotonic solution of 80mM [1-¹³C]-pyruvate with neutral pH at 37°C. Five seconds after the dissolution a 350µL aliquot was injected through the tail-vein over 12 seconds. A single-slice axial carbon-13 chemical shift image was acquired using an 8x8 single-point CSI sequence with (TR/TE = 100/0.5ms, α = 15°), 25 seconds after the start of the injection (in-plane FOV = 25x25mm² and 8mm slice thickness). A custom outward spiral k-space phase encoding was used to acquire the center of the k-space every eleventh acquisition. Multiple FIDs acquired at k_xy = 0 were used to mitigate the blurring artifact associated with the T₁ decay, thus improving the localization of the spectra. A 4M [1-¹³C]-sodium lactate (Sigma Aldrich) phantom was placed inside the coil to ensure proper overlay of the carbon and proton images. Metabolites were quantified by integrating the peaks in the real spectra after zero and first order phasing and forth-order polynomial baseline correction. All data were processed using custom-made routines in MATLAB2014b (MathWorks Inc.). Proton images and processed carbon images were exported to DICOM format and overlaid in OsiriX 7.0.Figure 1 shows the T₂-weighted proton image. The white arrow shows the injury on the left kidney after IRI. Figures 2 and 3 show the pyruvate and lactate maps overlaid on the proton image. The scale for each image is normalized to its own maximum intensities. Figure 4 shows a map of the lactate-to-pyruvate ratios. The observed ratios over the injured and the healthy kidneys are 0.35 ± 0.05 and 0.19 ± 0.02 respectively. This suggests a ~75% increase in the lactate flux post IRI. Lower pyruvate intensity over the injured kidney also suggests impaired perfusion. Increased lactate post IRI has been associated with reduced pyruvate dehydrogenase (PDH) activity which would increase the lactate pool size [9]. Further study is required to confirm this in the case of renal IRI. For this initial study we used a basic, low resolution carbon imaging pulse sequence. However, given the excellent signal to noise, we can increase both the spatial and temporal resolutions without compromising quantification accuracy. This study demonstrates the feasibility of using HP [1-¹³C]-pyruvate as a marker to probe metabolic derangements associated with renal IRI.