A 72-year-old male is admitted with sepsis due to pneumonia. His creatinine rises from a baseline of 1.0 mg/dL to 2.5 mg/dL over 24 hours. Urine sodium is 10 mEq/L, and fractional excretion of sodium (FENa) is 0.5%. What is the most likely cause of his acute kidney injury?
✓ Correct Answer: Option B
Low urine sodium (<20 mEq/L) and a fractional excretion of sodium (FENa) less than 1% are classic indicators of pre-renal azotemia, reflecting appropriate renal sodium reabsorption in response to hypoperfusion.