Renal aspects of the term and preterm infant: a selective update

This review discusses new aspects of normal and abnormal renal development that expand insight into the adaptation of the neonatal kidneys to the stress of extrauterine life. Highlighted are some pitfalls in measuring glomerular filtration rate in the neonate mainly caused by postnatal fluctuations in serum creatinine levels. Serum creatinine levels are correlated with the authors' recent finding of tubular reabsorption of creatinine in the immature neonatal kidney. Renal maldevelopment in premature and small-for-date babies has been shown related to serious medical problems in adult life, including hypertension. This finding presents the pediatrician with a new role in the time-honored vocation of preventing disease. Mutations in several genes may be responsible for most cases of congenital or hereditary renal aberrations. Two renal disorders, congenital nephrotic syndrome and neonatal acute renal failure, and one form of treatment modality of newborn infants, renal replacement therapy, are discussed in detail. These conditions are rare in general pediatric practice, but they illustrate some of the new developments in the renal care of the newborn. A word of caution is offered about the use of nonsteroidal anti-inflammatory drugs during pregnancy and the newborn period. All nonsteroidal anti-inflammatory drugs administered indirectly to the unborn fetus and directly to the young newborn impair renal structure (fetus) and function (both fetus and newborn). The new data have been obtained with genetic and molecular biology techniques and with established methods of developmental renal physiology. A better understanding of the pathogenesis of neonatal renal disorders will result in new diagnostic procedures and improved preventive and therapeutic possibilities relevant to the neonate with a renal disorder.