Acute Kidney Injury USMLE Step 1 Practice Question

A 72-year-old man with a 10-year history of hypertension and type 2 diabetes mellitus presents to the emergency department with acute dyspnea, confusion, and oliguria 2 days after undergoing emergent cardiac catheterization with iodinated contrast for acute coronary syndrome. He was not adequately hydrated prior to the procedure. On examination, he is tachypneic (RR 24) and has bilateral crackles on lung auscultation. Vital signs: BP 158/92 mmHg, HR 108, O2 saturation 88% on room air. Laboratory studies show: serum creatinine 4.2 mg/dL (baseline 1.1 mg/dL), BUN 92 mg/dL, potassium 6.8 mEq/L, urine osmolality 320 mOsm/kg, and fractional excretion of sodium (FENa) 0.8%. Urinalysis shows muddy brown casts and pigmented granular casts. Which of the following is the most likely diagnosis?