Pathogenesis
what causes fluid accumulation in the interstitial space?
Understand the Forces
Capillary filtration: the movement of fluid from capillary to interstitial space, driven by the balance of hydrostatic pressure and oncotic pressure.
Hydrostatic pressure: the pressure exerted by the fluid within the blood vessels. It pushes fluid out of the capillaries into the surrounding interstitial space.
Colloid ncotic pressure: the pressure exerted by protein (mostly albumin), drawing fluid back into capillary from the interstitial space
Pathogenesis
when capillary filtration exceeds the fluid removed via lymphatic drainage
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Lymphatic drainage normally helps remove excess fluid from interstitial space and return it to the circulatory system. When the lymphatic system is obstructed, fluid can’t be drained and buildup in interstitial space.
when intravascular hydrostatic pressure increases
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When hydrostatic pressure is too high, more fluid are being pushed into the interstitial space, overwhelming the lymphatic system, causes fluid to accumulate.
when the permeability of the endothelial barrier increases
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The lining of endothelium controls the movement of substances between blood and surrounding tissue
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When this barrier becomes leaky (maybe due to inflammation), more fluid and protein leak into interstitial space, causing edema or even anasarca
when oncotic pressure within the capillary/ decreases:
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When oncotic pressure is low, not in balance with hydrostatic pressure, less fluid is drawn back to the capillary but instead in the interstitial space, causing edema or anasarca
