RT Book, Section A1 Hanna, Melisha G. A1 Bock, Margret E. A2 Hay Jr., William W. A2 Levin, Myron J. A2 Abzug, Mark J. A2 Bunik, Maya SR Print(0) ID 1172107918 T1 Fluid, Electrolyte, & Acid–Base Disorders & Therapy T2 Current Diagnosis & Treatment: Pediatrics, 25e YR 2020 FD 2020 PB McGraw-Hill Education PP New York, NY SN 9781260457827 LK accesspediatrics.mhmedical.com/content.aspx?aid=1172107918 RD 2024/04/23 AB Total body water (TBW) constitutes 50%–75% of the total body mass, depending on age, sex, and fat content. After an initial brisk postnatal diuresis, the TBW slowly decreases to the adult range near puberty. TBW is divided into the intracellular and extracellular spaces. Intracellular fluid (ICF) accounts for two-thirds of the TBW and extracellular fluid (ECF) for one-third. The ECF is further compartmentalized into plasma (intravascular) volume and interstitial fluid (ISF).