Initial Experience of Metabolic Imaging With Hyperpolarized [1-¹³C]pyruvate MRI in Kidney Transplant Patients

Background: Kidney transplant is the treatment of choice for patients with end-stage renal disease. Early detection of allograft injury is important to delay or prevent irreversible damage.

Purpose: To investigate the feasibility of hyperpolarized (HP) [1-¹³C]pyruvate MRI for assessing kidney allograft metabolism.

Study type: Prospective.

Subjects: Six participants (mean age, 45.2 ± 12.4 years, two females) scheduled for kidney allograft biopsy and five patients (mean age, 59.6 ± 10.4 years, two females) with renal cell carcinoma (RCC).

Field strength/sequence: Three Tesla, T2-weighted fast spin echo, multi-echo gradient echo, single shot diffusion-weighted echo-planar imaging, and time-resolved HP ¹³C metabolite-selective imaging.

Assessment: Five of the six kidney allograft participants underwent biopsy after MRI. Estimated glomerular filtration rate (eGFR) and urine protein-to-creatine ratio (uPCR) were collected within 4 weeks of MRI. Kidney metabolism was quantified from HP [1-¹³C]pyruvate MRI using the lactate-to-pyruvate ratio in allograft kidneys and non-tumor bearing kidneys from RCC patients.

Statistical tests: Descriptive statistics (mean ± SD).

Results: Biopsy was performed a mean of 9 days (range 5-19 days) after HP [1-¹³C]pyruvate MRI. Three biopsies were normal, one showed low-grade fibrosis and one showed moderate microvascular inflammation. All had stable functioning allografts with eGFR >60 mL/min/1.73 m² and normal uPCR. One participant who did not undergo biopsy had reduced eGFR of 49 mL/min/1.73 m² and elevated uPCR. The mean lactate-to-pyruvate ratio was 0.373 in participants with normal findings (N = 3) and 0.552 in participants with abnormal findings (N = 2). The lactate-to-pyruvate ratio was highest (0.847) in the participant with reduced eGFR and elevated uPRC. Native non-tumor bearing kidneys had a mean lactate-to-pyruvate ratio of 0.309.

Data conclusion: Stable allografts with normal findings at biopsy showed lactate-to-pyruvate ratios similar to native non-tumor bearing kidneys, whereas allografts with abnormal findings showed higher lactate-to-pyruvate ratios.

Evidence level: 2 TECHNICAL EFFICACY: Stage 2.