Calculation of interstitial fluid in a 50 years old is done by?

Calculation of interstitial fluid in a 50
years old is done by?
a) TBW minus ECF
b) ECF minus plasma volume
c) ICF minus ECF
d) TBW minus ICF
Correct Answer - B
Ans. B. ECF minus plasma volume.
[Ref Ganong 23th/e p. 3-6; Guyton 12th/e p. 286-288]
Most of the fluid is calculated directly by dilution method, except for
intracellular fluid (ICF) and interstitial fluid.
Both these are calculated indirectly by calculating other body fluids.
ICF = Total body water volume - ECF volume Interstitial fluid = ECF
volume - Plasma volume.