A nurse is reviewing the BUN result of a client who is taking cyclosporine following a kidney transplant. Which of the following laboratory studies should the nurse recognize as another renal function study that should be monitored?

A. Creatinine is a key indicator of kidney function. Elevated serum creatinine levels suggest impaired renal filtration, which is a potential adverse effect of cyclosporine (a nephrotoxic immunosuppressant). Monitoring both BUN and creatinine provides a comprehensive view of renal health. B. Bilirubin reflects liver function, not renal function. C. Amylase assesses pancreatic activity, useful for diagnosing pancreatitis, not kidney function. D. Alkaline phosphatase (ALP) indicates liver or bone disorders, unrelated to renal function monitoring.