Neonatal kidney size and function in preterm infants: what is a true estimate of glomerular filtration rate?

J Pediatr. 2014 May;164(5):1026-1031.e2. doi: 10.1016/j.jpeds.2014.01.044. Epub 2014 Mar 5.


Objectives: 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.

Study design: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute Kidney Injury / blood
  • Acute Kidney Injury / diagnosis
  • Acute Kidney Injury / physiopathology
  • Biomarkers / blood
  • Creatinine / blood*
  • Cross-Sectional Studies
  • Cystatin C / blood*
  • Female
  • Gestational Age
  • Glomerular Filtration Rate*
  • Humans
  • Infant, Newborn
  • Infant, Premature / blood
  • Infant, Premature / physiology*
  • Kidney / anatomy & histology*
  • Kidney / diagnostic imaging
  • Kidney / physiopathology
  • Linear Models
  • Male
  • Multivariate Analysis
  • Organ Size
  • Reference Values
  • Ultrasonography


  • Biomarkers
  • Cystatin C
  • Creatinine