Third-space sequestration is associated with which condition?

• A. Intestinal obstruction
• B. Pulmonary embolism
• C. Hypothyroidism
• D. Hypovolemia due to dehydration

Answer: (A)

Third-space sequestration means fluid shifts from the intravascular space into nonfunctional compartments like the peritoneal cavity or interstitial tissues. This redistribution is especially prominent in abdominal catastrophes such as intestinal obstruction, where bowel distention, secretions, and venous congestion drive fluid into the gut wall and peritoneal space, causing significant intravascular volume loss that can be disproportionate to external losses. That makes intestinal obstruction the condition most closely linked to third-space sequestration. Pulmonary embolism centers on a vascular blockage in the lungs rather than large-scale fluid moving into third spaces. Hypothyroidism can cause edema (myxedema) from mucopolysaccharide deposition, not the acute third-space fluid shift. Dehydration from external fluid losses reduces intravascular volume without the characteristic shift into nonfunctional third spaces.