A gunshot wound patient is in the ICU after surgery. Which data suggests acute renal failure?

• A. Urine Output of 400 ml/24 hours
• B. Urine Output of 1200 ml/24 hours
• C. Urine Output of 2000 ml/24 hours
• D. Normal Urine Output

Answer: (A)

Oliguria, or markedly reduced urine output, signals acute kidney injury in a patient who’s critically ill or recovering from surgery. When the kidneys aren’t receiving enough blood flow or have been damaged, they can’t filter urine effectively, so output drops. In this post‑op ICU setting, a very low daily urine volume points to acute renal failure because it reflects impaired filtration and fluid/electrolyte balance.

Higher urine output or a normal amount would be less consistent with AKI in this context; polyuria might suggest other problems like diabetes insipidus or diuretic effects, while normal output does not rule out kidney injury if creatinine is rising. The key idea is that a small amount of urine over 24 hours indicates reduced kidney function needing prompt assessment and management.