ECFvolym

ECFvolym, or extracellular fluid volume, is a medical term describing the amount of fluid located outside cells in the body. It is a key component of body fluid compartments and an important parameter in assessing hydration, fluid balance, and circulatory status.

The extracellular fluid volume includes plasma (intravascular fluid), interstitial fluid, and transcellular fluids such as cerebrospinal, pleural, peritoneal, and gastrointestinal secretions. In a typical healthy adult weighing about 70 kg, the ECF volume is around 14 liters, approximately 20% of body weight. Plasma volume accounts for about 3 liters, while interstitial fluid makes up the remainder of the ECF.

Regulation of ECFvolym depends on renal function, sodium balance, and hormonal control. Osmoregulation and thirst drive water intake, while antidiuretic hormone (ADH), aldosterone, and atrial natriuretic peptide (ANP) adjust water and sodium excretion. Changes in ECFvolym influence blood pressure, tissue perfusion, and edema formation.

Measurement of ECFvolym can be accomplished by indicator-dilution techniques using non-penetrating markers such as inulin, mannitol, or sucrose, which mix with ECF but do not enter cells. Modern assessments may employ bioimpedance analysis or clinical estimates based on body weight changes, signs of edema, and laboratory data.

Clinical significance of ECFvolym lies in detecting dehydration (reduced ECF), fluid overload or edema (increased ECF), and guiding management in conditions such as heart failure, kidney disease, liver cirrhosis, and severe acute illness. The concept is closely linked to osmolality, sodium balance, and overall fluid homeostasis.