title: Assessment of fractional excretion of urea for early diagnosis of cardiac surgery associated acute kidney injury.
abstract: BACKGROUND
  Acute kidney injury (AKI) is a common complication after cardiac surgery (CS). Recently, neutrophil gelatinase-associated lipocalin (NGAL) was shown to predict AKI development earlier than serum creatinine, but it is not widely used in clinical practice. Fractional excretion of urea (FeU) has been referred to as a useful tool to discriminate between prerenal and established AKI. The aim of our study is to evaluate the sensitivity and specificity of FeU, in the early diagnosis of AKI in patients undergoing CS.
  
  
  METHODS
  We performed a prospective study on adults undergoing CS. AKI was defined by AKIN criteria. Individuals suffering from CKD, were excluded. Sensitivity and specificity of FeU, fractional excretion of sodium (FeNa) and urine NGAL, measured at 1, 6 and 24 h following CS, were assessed.
  
  
  RESULTS
  We included 66 patients (26% female) aging 68 ± 11 years. AKI prevalence was 24% and mortality was 3.28%. Patients with AKI had a significantly lower FeU compared to those without AKI (23.89 ± 0.67% vs. 34.22 ± 0.58%; p < 0.05) 6 h after CS, but not at the 1- and 24-h time points. NGAL was also statistically significant between both groups. FeU showed a 75% sensitivity and 79.5% specificity; the AUC was 0.786. ROC analysis of FeU and NGAL yielded similar values (p = NS).
  
  
  CONCLUSIONS
  FeU is useful as an early biomarker to predict AKI after CS and it is comparable to the new biomarker NGAL.
authors.affiliation: a Servicio de Nefrología del Hospital Italiano de Buenos Aires , Buenos Aires , Argentina .
authors.forename: Carlos Federico
authors.initials: CF
authors.lastname: Varela
authors.affiliation: a Servicio de Nefrología del Hospital Italiano de Buenos Aires , Buenos Aires , Argentina .
authors.forename: Gustavo
authors.initials: G
authors.lastname: Greloni
authors.affiliation: a Servicio de Nefrología del Hospital Italiano de Buenos Aires , Buenos Aires , Argentina .
authors.forename: Carlos
authors.initials: C
authors.lastname: Schreck
authors.affiliation: a Servicio de Nefrología del Hospital Italiano de Buenos Aires , Buenos Aires , Argentina .
authors.forename: Griselda
authors.initials: G
authors.lastname: Bratti
authors.affiliation: a Servicio de Nefrología del Hospital Italiano de Buenos Aires , Buenos Aires , Argentina .
authors.forename: Angel
authors.initials: A
authors.lastname: Medina
authors.affiliation: b Servicio de Cirugía Cardiovascular del Hospital Italiano de Buenos Aires , Buenos Aires , Argentina , and.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Marenchino
authors.affiliation: c Servicio de Cardiología del Hospital Italiano de Buenos Aires , Buenos Aires , Argentina.
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Pizarro
authors.affiliation: c Servicio de Cardiología del Hospital Italiano de Buenos Aires , Buenos Aires , Argentina.
authors.forename: Cesar
authors.initials: C
authors.lastname: Belziti
authors.affiliation: a Servicio de Nefrología del Hospital Italiano de Buenos Aires , Buenos Aires , Argentina .
authors.forename: Guillermo
authors.initials: G
authors.lastname: Rosa-Diez
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood / Q000175:diagnosis* / Q000209:etiology* / Q000652:urine; D000209:Acute-Phase Proteins / Q000652:urine; D000368:Aged; D015415:Biomarkers / Q000097:blood / Q000652:urine; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D042241:Early Diagnosis; D005260:Female; D006801:Humans; D000071068:Lipocalin-2; D054834:Lipocalins / Q000652:urine; D008297:Male; D011446:Prospective Studies; D011518:Proto-Oncogene Proteins / Q000652:urine; D012680:Sensitivity and Specificity; D014508:Urea / Q000097:blood* / Q000652:urine*
chemical_list: D000209:Acute-Phase Proteins; D015415:Biomarkers; C489506:LCN2 protein, human; D000071068:Lipocalin-2; D054834:Lipocalins; D011518:Proto-Oncogene Proteins; D014508:Urea
keywords: Acute kidney injury; NGAL; cardiovascular surgery; fractional excretion of urea