A 72-year-old man with chronic kidney disease stage 3 (baseline creatinine 2.0 mg/dL) undergoes elective coronary angiography for stable angina. He receives 150 mL of iodinated contrast medium. On post-procedure day 2, his serum creatinine rises to 2.8 mg/dL and urine output is 1.2 mL/kg/hr. Urine dipstick shows no protein or blood. Urine osmolality is 320 mOsm/kg and urine sodium is 45 mEq/L. What is the most likely diagnosis?