title: Neonatal kidney size and function in preterm infants: what is a true estimate of glomerular filtration rate?
abstract: OBJECTIVE
  To distinguish between cystatin C (CysC) and creatinine (Cr) as markers of estimated glomerular filtration rate (eGFR) in preterm infants and to correlate eGFR with total kidney volume (TKV) as a surrogate of nephron mass.
  
  
  METHODS
  Sixty preterm (<37 weeks' gestational age [GA]) and 40 term infants were enrolled at birth. Serum Cr and CysC levels were assessed during the first week of life. Renal ultrasounds were performed to assess kidney dimensions with calculation of the TKV as a surrogate of nephron mass. Six equations derived from reference inulin, iohexol, and iothalamate clearance studies were used to calculate eGFR. Multiple regression analysis was applied to assess the relative impact of neonatal measures on eGFR, including TKV, GA, and mean arterial pressure (MAP).
  
  
  RESULTS
  Renal lengths correlated with GA and were within the reference values for intrauterine measurements. Estimation equations for glomerular filtration rate (GFR) based on Cr, CysC, and combined CysC + Cr demonstrated that Cr-based equations consistently underestimated GFR, whereas CysC and combined equations were more consistent with referenced inulin clearance studies. Term infants demonstrated significantly better eGFR than preterm infants. TKV, GA, and MAP correlated positively with eGFR, although only MAP and GA remained significant when adjusted for other covariates.
  
  
  CONCLUSIONS
  Primary determinants of eGFR in preterm infants are GA and MAP. The CysC level is a superior biomarker to serum Cr in the assessment of GFR in premature infants.
authors.affiliation: Division of Pediatric Nephrology, University of Miami/Holtz Children's Hospital, Miami, FL. Electronic address: cabitbol@med.miaim.edu.
authors.forename: Carolyn L
authors.initials: CL
authors.lastname: Abitbol
authors.affiliation: Division of Pediatric Nephrology, University of Miami/Holtz Children's Hospital, Miami, FL.
authors.forename: Wacharee
authors.initials: W
authors.lastname: Seeherunvong
authors.affiliation: Division of Neonatology, University of Miami/Holtz Children's Hospital, Miami, FL.
authors.forename: Marta G
authors.initials: MG
authors.lastname: Galarza
authors.affiliation: Division of Pediatric Nephrology, University of Miami/Holtz Children's Hospital, Miami, FL.
authors.forename: Chryso
authors.initials: C
authors.lastname: Katsoufis
authors.affiliation: Division of Pediatric Nephrology, University of Miami/Holtz Children's Hospital, Miami, FL.
authors.forename: Denise
authors.initials: D
authors.lastname: Francoeur
authors.affiliation: Division of Pediatric Nephrology, University of Miami/Holtz Children's Hospital, Miami, FL.
authors.forename: Marissa
authors.initials: M
authors.lastname: Defreitas
authors.affiliation: Division of Pediatric Nephrology, University of Miami/Holtz Children's Hospital, Miami, FL.
authors.forename: Alcia
authors.initials: A
authors.lastname: Edwards-Richards
authors.affiliation: Division of Pediatric Nephrology, University of Miami/Holtz Children's Hospital, Miami, FL.
authors.forename: Vimal
authors.initials: V
authors.lastname: Master Sankar Raj
authors.affiliation: Division of Pediatric Nephrology, University of Miami/Holtz Children's Hospital, Miami, FL.
authors.forename: Jayanthi
authors.initials: J
authors.lastname: Chandar
authors.affiliation: Division of Neonatology, University of Miami/Holtz Children's Hospital, Miami, FL.
authors.forename: Shahnaz
authors.initials: S
authors.lastname: Duara
authors.affiliation: Division of Perinatology and Obstetrics, University of Miami/Holtz Children's Hospital, Miami, FL.
authors.forename: Salih
authors.initials: S
authors.lastname: Yasin
authors.affiliation: Division of Pediatric Nephrology, University of Miami/Holtz Children's Hospital, Miami, FL.
authors.forename: Gaston
authors.initials: G
authors.lastname: Zilleruelo
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood / Q000175:diagnosis / Q000503:physiopathology; D015415:Biomarkers / Q000097:blood; D003404:Creatinine / Q000097:blood*; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005865:Gestational Age; D005919:Glomerular Filtration Rate; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000097:blood / Q000502:physiology*; D007668:Kidney / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000503:physiopathology; D016014:Linear Models; D008297:Male; D015999:Multivariate Analysis; D009929:Organ Size; D012016:Reference Values; D014463:Ultrasonography
chemical_list: D015415:Biomarkers; D055316:Cystatin C; D003404:Creatinine