title: Utility of fractional excretion of urea in the differential diagnosis of acute kidney injury in children.
abstract: The fractional excretion of sodium (FENa) has been used as an index for the differential diagnosis of acute tubular necrosis (ATN) and prerenal acute kidney injury (AKI). The reliability of this index, however, decreases with the use of the diuretic agent furosemide. The fractional excretion of urea nitrogen (FEUN) has been shown to be useful in such settings in adults. The objective of this study was to examine whether FEUN is also useful in these settings in children.
  
  
  
  We assessed 102 episodes of AKI in 74 children, classifying these into three groups based on history, physical examination, urine examination and subsequent clinical course: (1) prerenal AKI without furosemide (N = 37), (2) prerenal AKI with furosemide (N = 32) and (3) ATN (N = 33).
  
  
  
  Of the 37 prerenal AKI episodes without furosemide, 35 showed low FENa of <1 %, with an overall average of 0.35 ± 0.11 %, whereas prerenal AKI with furosemide (1.63 ± 0.37 %) and ATN (8.76 ± 2.11 %) were associated with a higher FENa. FEUN in the clinical setting of prerenal AKI was lower than that in ATN (27.9 ± 2.1 vs. 51.6 ± 3.8 %, respectively) and, in contrast to FENa, not significantly different between the categories of prerenal AKI with and without furosemide (29.2 ± 3.1 vs. 25.1 ± 2.9, respectively). The sensitivity of FEUN <35 % was 75 % in prerenal AKI with furosemide, whereas that of FENa was 53 %.
  
  
  
  FEUN is useful in detecting prerenal AKI in children administered furosemide.
authors.affiliation: Department of Pediatrics, Hiratsuka Kyosai Hospital, Kanagawa, Japan.
authors.forename: Hisayo
authors.initials: H
authors.lastname: Fujita
authors.affiliation: Department of Pediatrics, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Shinjoh
authors.affiliation: Department of Pediatrics, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Ishii
authors.affiliation: Department of Pediatrics, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. awazu@keio.jp.
authors.forename: Midori
authors.initials: M
authors.lastname: Awazu
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood / Q000188:drug therapy / Q000652:urine*; D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D004232:Diuretics / Q000627:therapeutic use; D005260:Female; D005665:Furosemide / Q000627:therapeutic use; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012964:Sodium / Q000097:blood / Q000652:urine; D014508:Urea / Q000097:blood / Q000652:urine*
chemical_list: D004232:Diuretics; D005665:Furosemide; D014508:Urea; D012964:Sodium
keywords: Acute kidney injury; Acute tubular necrosis; Blood urea nitrogen-to-creatinine ratio; Fractional excretion of sodium; Fractional excretion of urea; Furosemide