skip to main content

ATN AKI — RACP Adult Medicine MCQ

Instant feedback + full explanation. One question, done properly.

EasyNephrologyATN AKIRACP Adult Medicine

A 55-year-old man develops AKI 48 hours after gentamicin therapy for endocarditis. Creatinine 380 μmol/L. Urine Na⁺ 60 mmol/L. FeNa 4%. Urine microscopy shows muddy brown granular casts. Urine osmolality 320 mOsm/kg. What is the AKI type?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: C — Intrinsic renal (ATN)

High urine Na⁺ (>40), high FeNa (>2%), muddy brown casts (pathognomonic for ATN), and isosthenuria (urine osmolality ~300) after nephrotoxin exposure (aminoglycoside) is intrinsic AKI from ATN. Damaged tubules cannot reabsorb Na⁺ or concentrate urine. Treatment: supportive (avoid further nephrotoxins, optimise volume, dialysis if needed). Most ATN recovers in 1-3 weeks.

Reference: KDIGO – 2024 – AKI