Information on Renal Function:
From: Essentials in Pediatric Urology, 2012: 9-20 ISBN: 978-81-308-0511-5 Editor: George Sakellaris
The development of renal function by Maria Bitsori, Specialist Paediatrician & Consultant Paediatric Nephrologist, Department of Paediatrics University Hospital of Heraklion, Greece.
“Summary. Renal function starts to develop in foetal period and continues to evolve throughout the first years of life until it reaches its complete, adult level. Under this process the kidneys are obliged to changes that give the renal function during childhood its particular characteristics. The human kidney begins to develop in the 5th gestational week and starts to produce urine between the 10th and 12th week of gestation. Nephrogenesis is complete around the 35th- 36th week so that a term neonate is born with all its nephrons, something which is not the case for a premature one, born before nephrogenesis is complete. The entire process of foetal kidney development has been recently shown to be regulated by many genes and gene products, such as cytokines and growth factors, as well as the intrauterine environment itself, in a particular way known as epigenetics.
The kidney regulates homeostasis by two fundamental functions, the glomerular and the tubular. In neonates both functions are deficient and although the neonatal kidneys are well equipped to sustain physiological processes, they are severely limited in their response to stress. Neonates have glomerular filtration rate (GFR) as low as 20 ml/min/1.73 m2 at birth, which rises gradually to reach the adult rates at 18 months. Additionally, due to immature tubular function, neonates have reduced concentrating capacity, negative sodium equilibrium and reduced bicarbonate levels and they are, thus, prone to dehydration and hyponatremia.
No new nephrons are made during childhood but the existing ones grow in size and mature in function. Although glomerular and tubular function evolve to mature levels between 12-18 months, the child kidney keeps lower adaptation capacities and remains vulnerable to injuries throughout childhood.”
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Arant BS Jr1. “Several aspects of renal function vary considerably during the 1st year of life and differ markedly from the equivalent values in the adult. Glomerular filtration rate (GFR) increases little, prior to the time an infant reaches a conceptional age of 34 weeks, the point in renal development from which the absolute GFR (ml/min) increases gradually to mature values when linear growth is completed during adolescence.”