Renal Function in Full-Term Neonates with Hyperbilirubinemia

The purpose of this study was to investigate the effect of unconjugated hyperbilirubinemia on endogenous creatinine clearance and urinary excretion of sodium, phosphorus, lysozyme, and amino acids in full-term infants. Thirty-seven healthy, breast-fed newborns who were not exposed to phototherapy were studied on their third to fifth day of life. Twenty had neonatal hyperbilirubinemia with a mean indirect bilirubin value of 16.4 mg/dl, whereas 17 who were used as controls had a mean indirect bilirubin value of 7.8 mg/dl. Urine was collected, and samples were taken for examination of creatinine, lysozyme, sodium, and phosphorus concentration. Urinary sediment, glucose, and amino acid levels were also measured. Serum total and direct bilirubin, creatinine, sodium, and phosphorus measurements were taken at the beginning of urine collection. Calculations were made for creatinine clearance, fractional excretion of sodium (FENa), and tubular reabsorption of renal phosphate per deciliter glomerular filtrate (TP/GFR). The means (± 1 SD) of creatinine clearance, FENa, and TP/GFR were 27.0 ± 14.2 ml/min/1.73 m², 0.53% ± 0.49%, and 5.72 ± 1.16 mg/dl GF, respectively, in the hyperbilirubinemic group compared with 21.1 ± 9.4 ml/min/1.73 m², 0.4% ± 0.47%, and 6.01 ± 0.51 mg/dl GF, respectively, in the controls. No statistically significant differences were found between the groups for any of the examined parameters of either glomerular or tubular function. Neonatal hyperbilirubinemia <20.8 mg/dl has no detrimental effect on renal function of healthy, breast-fed, full-term newborns, and no modification in the approach regarding renal function is necessary in these babies.