Neonatal Kidney Size and Function in Preterm Infants: What Is a True Estimate of Glomerular Filtration Rate?

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 ( 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.