The Kidneys

Renal function is markedly diminished in neonates and further diminished in preterm babies because of low perfusion pressure and immature glomerular and tubular function ( Fig. 60-4 ). Nearly complete maturation of glomerular filtration and tubular function occurs by approximately 20 weeks after birth, although maturation is somewhat delayed in premature infants. Complete maturation of renal function occurs by about 2 years of age.^{[21] [22]} Thus, the ability to handle free water and solute loads may be impaired in neonates, and the half-life of medications excreted by means of glomerular filtration will be prolonged.^{[23] [24] [25]}