In pediatric kidney transplant patients, rejection, medication toxicity and ischemia cause early and chronic renal allograft injury, which reduces graft lifespan and patient survival. Early detection of injury would facilitate prevention and treatment. The gold standard surveillance biopsy has limitations including delayed discovery of injury. No noninvasive test identifies graft injury before it is clinically apparent. This project's goal is to develop a novel early marker of subclinical graft injury to facilitate prompt recognition and treatment.