title: Fractional excretion of urea as a diagnostic index in acute kidney injury in intensive care patients.
abstract: OBJECTIVE
  Acute kidney injury (AKI) is a dynamic process that evolves from an early reversible condition to an established disease. Value of urine indices in the event of AKI is uncertain in critically ill patients. The aim of this study was to evaluate the performance of fractional excretion of urea (FeU) for differentiating persistent from transient AKI in patients admitted to the intensive care unit.
  
  
  METHODS
  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 3 days after inclusion. Persistent AKI was defined as persistent serum creatinine elevation or oliguria.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  Fractional excretion of urea less than 40% was found to be a sensitive and specific index in differentiating transient from persistent AKI in intensive care unit patients especially if diuretics had been administered.
authors.affiliation: Centre Hospitalier Universitaire de Bordeaux, Department of Anaesthesiology and Intensive Care Medicine, Place Amélie Raba-Léon, 33000 Bordeaux, France. antoine.dewitte@chu-bordeaux.fr
authors.forename: Antoine
authors.initials: A
authors.lastname: Dewitte
authors.forename: Matthieu
authors.initials: M
authors.lastname: Biais
authors.forename: Laurent
authors.initials: L
authors.lastname: Petit
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Cochard
authors.forename: Gilles
authors.initials: G
authors.lastname: Hilbert
authors.forename: Christian
authors.initials: C
authors.lastname: Combe
authors.forename: François
authors.initials: F
authors.lastname: Sztark
mesh_terms: D058186:Acute Kidney Injury / Q000175:diagnosis*; D000368:Aged; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D062072:Patient Acuity; D012372:ROC Curve; D012307:Risk Factors; D012680:Sensitivity and Specificity; D014508:Urea / Q000652:urine*; D016482:Urinalysis
chemical_list: D014508:Urea