10. Water Balance

  1. Charles G. D. Brook MA, MD, FRCP, FRCPCH1 and
  2. Mehul T. Dattani MD, FRCP, FRCPCH, DCH2,3

Published Online: 23 FEB 2012

DOI: 10.1002/9781119968153.ch10

Handbook of Clinical Pediatric Endocrinology, Second Edition

Handbook of Clinical Pediatric Endocrinology, Second Edition

How to Cite

Brook, C. G. D. and Dattani, M. T. (2012) Water Balance, in Handbook of Clinical Pediatric Endocrinology, Second Edition, Wiley-Blackwell, Oxford, UK. doi: 10.1002/9781119968153.ch10

Author Information

  1. 1

    University College London, London, UK

  2. 2

    Developmental Endocrinology Research Group, Clinical and Molecular Genetics Unit, UCL Institute of Child Health, UK

  3. 3

    Great Ormond Street Hospital for Children, London and University College London Hospitals, UK

Publication History

  1. Published Online: 23 FEB 2012
  2. Published Print: 13 APR 2012

ISBN Information

Print ISBN: 9780470657881

Online ISBN: 9781119968153



  • body water;
  • cerebral salt wasting;
  • desamino-D-arginine vasopressin (DDAVP);
  • diabetes insipidus;
  • hypernatremia;
  • hyponatremia;
  • nephrogenic diabetes insipidus;
  • polydipsia;
  • renin-angiotensin-aldosterone pathway;
  • syndrome of inappropriate antidiuretic hormone (SIADH);
  • vasopressin


The maintenance of normal fluid balance is essential to life. Water intake and excretion vary widely in normal persons but plasma osmolality is maintained strictly within the range of 275–295 mOsm/kg. Plasma osmolality above or below the range results in alterations in intracellular solute concentrations, patterns of cellular depolarization, cell morphology and critical aspects of cell function that can become life-threatening. This chapter explains how thirst controls water intake and arginine vasopressin controls urine concentration in order to limit excursions in osmolality. Intact function of either thirst or vasopressin secretion can maintain normal plasma osmolality independently with adequate access to water. The regulation of extracellular fluid volume is primarily under the control of the renin-angiotensin-aldosterone system and occurs by modulation of sodium intake and excretion, in contrast to the regulation of osmolality by water intake and excretion. Both hyponatremia and hypernatremia should be carefully corrected over a period of 24-48 h.