Antimicrobials USMLE Step 1 Practice Question
A 64-year-old man with chronic kidney disease (baseline creatinine 2.1 mg/dL, CrCl 25 mL/min) presents to the hospital with fever (38.9°C), hypotension (88/54 mmHg), and tachycardia (118 bpm). Blood cultures grow Escherichia coli. He is treated with gentamicin 5 mg/kg IV as a single daily dose. On hospital day 5, his serum creatinine rises to 3.8 mg/dL. Urinalysis shows muddy brown casts and fine granular casts. The fractional excretion of sodium is 3.2%. Urine output remains 1.2 mL/kg/hr. Which of the following best explains the mechanism of this patient's acute kidney injury?
Answer choices
- APrerenal azotemia from sepsis-induced reduction in renal perfusion pressure
- BAcute interstitial nephritis from drug hypersensitivity reaction
- CAccumulation of aminoglycoside in proximal tubule cells causing acute tubular necrosisCorrect answer
- DPost-infectious glomerulonephritis with immune complex deposition
- ERhabdomyolysis-induced myoglobinuria and tubular obstruction
- FHyperkalemia-induced inhibition of the Na-K-ATPase pump
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