Fractional excretion of urea as a diagnostic index in acute kidney injury in intensive care patients

Journal of Critical Care, 04/23/2012

Dewitte A et al. – Fractional excretion of urea less than 40% was found to be a sensitive and specific index in differentiating transient from persistent acute kidney injury (AKI) in intensive care unit patients especially if diuretics had been administered.


  • This was an observational study.
  • Forty-seven patients with AKI according to the RIFLE classification were included.
  • Transient AKI was defined as AKI resolved within 3days after inclusion.
  • Persistent AKI was defined as persistent serum creatinine elevation or oliguria.


  • Fractional excretion of urea was lower in case of transient, 33% (25-39), than persistent AKI, 47% (36-61) (P=.001).
  • Areas under the receiver operating characteristic curve for FeU in case of transient AKI were better than those for other urinary indexes, 0.78 (95% confidence interval, 0.63-0.92).
  • Optimal cutoff point according to the receiver operating characteristic curve was 40%.
  • In patients treated with diuretics, FeU was the only predictive index of transient AKI.
  • Fractional excretion of urea gradually increased from days 1 to 7 in transient AKI, whereas plasma creatinine decreased.

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