A 65-year-old man has urine output of 10 mL/h following abdominal aortic aneurysmectomy. Acute tubular necrosis is suggested by the presence of which of the following?

A. Urine osmolality of more than 500 mOsm/kg

B. Urine sodium of more than 40 mEq/L

C. Fractional excretion of sodium of <1%

D. Blood urea nitrogen (BUN)-to-serum creatinine ratio (SCR) of more than 20

Correct Answer: Urine sodium of more than 40 mEq/L

Description: Oliguria may be prerenal or renal. The following table characterizes findings in prerenal failure versus those observed in intrinsic renal failure (acute tubular necrosis).PRERENAL VS. INTRINSIC RENAL FAILURE Prerenal FailuresIntrinsic Renal FailuresUrine osmolality (mOsm/kg)>500<350Urine sodium (mEq/L)<20>40Fractional excretion of sodium<1%>2%BUN/SCR>20<10Urine/PCR>40<20

Category: Surgery

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