Assessment of Renal Function in Newborn Infants
James E. Springate MD1
Robert D. Fildes MD1
Leonard G. Feld MD, PhD1
1 Buswell fellow in pediatric nephrology at The State University of New York at Buffalo, School of Medicine
Proper interpretation of renal function tests in newborn infants requires knowledge of conceptual age. A plasma creatinine concentration of 1.2 mg/dL, serum bicarbonate concentration of 16 mEq/L, and a fractional excretion of sodium of 5% is normal in a 2-week-old infant born at 28 weeks's gestational age but markedly abnormal in a 2-week-old baby born at term.
Newborn infants with urinary tract infections need radiologic evaluation for vesicoureteral reflux and urinary tract obstruction using voiding cystourethrogram and renal sonography or radionuclide scanning. Intravenous pyebography is not the test of choice for this evaluation.
If severe hypertension develops in a 1-week-old infant, seriously ill with respiratory distress syndrome, evaluation should include determination of the use of umbilical artery catheters and investigation for renal artery thrombosis with sonography and radionuclide scanning because renovascular disease is the major cause of hypertension in newborn infants.