Third Spacing – fluid shift in body cavities

3rd spacing – transcellular spacing


extracellular fluids are distributed between the interstitial compartment (i.e. tissue) and intravascular compartment (i.e. plasma) in an approximately 75%-25% ratio.


Third spacing is the physiological concept that body fluids may collect in a “third” body compartment that isn’t normally perfused with fluids.


For example, with severe burns, fluids may pool in the burn site and cause depletion of the fluids in the first and second compartments.


With pancreatitis, fluids may “leak out” into the peritoneal cavity, also causing depletion of the first and second compartments.

Patients who undergo long, difficult operations in large surgical fields collect third-space fluids and become intravascularly depleted despite large volumes of intravenous fluid and blood replacement.


Third Spacing: the accumulation in spaces where fluid is not typically exchanged.


Third spaces are those where limited fluids exist in the body.

eg joint space – where fluid exchange does not typically occur here


  • Increase in abdominal girth
  • dull percussion above abdomen with signs of vascular depletion (abnormally rapid or extremly slow pulse).
  • serum albumin levels should be checked as low serum albumin levels result in fluid shifting out of vascular space because albumin normally maintains plasma colloid osmotic pressure within the blood vessels.



Removal of this fluid is very difficult – medical intervention is needed for removal

eg. lungs or peritoneum

Martin, Glenn and Porth, Carol, Mattson. 2009. Pathophysiology Concepts of Altered Health States. 8th ed. Lippincott Williams and Wilkins. Philadelphia


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