A 70-year-old male with a history of hypertension and diabetes is admitted for acute kidney injury after undergoing a coronary angiogram. His creatinine rose from 1.0 mg/dL to 3.5 mg/dL within 24 hours. Urinalysis shows muddy brown granular casts. What is the most likely cause of his acute kidney injury?
✓ Correct Answer: Option B
Acute tubular necrosis (ATN) is a common cause of intrinsic AKI, often precipitated by ischemia or nephrotoxins like contrast dye. Muddy brown granular casts are pathognomonic for ATN. Prerenal azotemia typically has bland urine sediment.