Acute Kidney Injury USMLE Step 1 Practice Question

A 72-year-old man with a history of hypertension, type 2 diabetes mellitus, and chronic kidney disease (baseline creatinine 1.4 mg/dL) undergoes cardiac catheterization via femoral access for evaluation of stable angina. During the procedure, he receives 180 mL of high-osmolality iodinated contrast. Within 24 hours, his urine output decreases to 80 mL/day. At 48 hours post-procedure, laboratory studies show: serum creatinine 4.2 mg/dL, BUN 74 mg/dL, potassium 5.8 mEq/L, and fractional excretion of sodium (FENa) 2.1%. Urinalysis demonstrates muddy brown casts, granular casts, and epithelial cell casts. Renal ultrasound shows normal-sized kidneys without hydronephrosis. Which of the following is the most likely diagnosis?