Water Balance and 'Salt Wasting' in the First Year of Life: The Role of Aldosterone-Signaling Defects

• In newborns and infants, dehydration and salt wasting represent a relatively common cause of admission to hospital and may result in life-threatening complications. Kidneys are responsible for electrolyte homoeostasis, but neonatal kidneys show low glomerular filtration rate and immaturity of the distal nephron, leading to reduced ability to concentrate urine. High extrarenal fluid losses often contribute to the increased occurrence of electrolyte disorders. Aldosterone is essential for sodium retention in the kidney, salivary glands, sweat glands and colon. A partial and transient aldosterone resistance is present in newborns and infants, thus reducing the capability of maintaining sodium balance in specific pathological conditions. The present review examines the mechanisms making infants more susceptible to salt wasting. Peculiar aspects of renal physiology in the first year of life and management of electrolyte disorders (i.e. sodium and potassium) are considered. Finally, inherited disorders associated with neonatal salt wasting are examined in detail.

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