colloïdosmotische

Colloïdosmotische druk, also known as colloid-osmotic pressure, is the component of osmotic pressure exerted by colloidal proteins in body fluids, primarily albumin, which are largely impermeable to the capillary wall. Because these proteins do not freely cross the capillary endothelium, they generate a pressure that tends to pull water from the interstitial space back into the vascular compartment.

In capillary exchange, the balance of Starling forces includes hydrostatic pressure that pushes fluid out of the capillaries and oncotic (colloidosmotic) pressure that draws it in. Plasma colloid osmotic pressure is higher than interstitial colloid osmotic pressure, which favors reabsorption of fluid into the capillaries, especially at the venous end, with lymphatic drainage helping to return excess interstitial fluid to the circulation.

Major contributors are plasma proteins, with albumin accounting for the largest share of the colloidosmotic pressure. Normal plasma COP is typically about 25-30 mmHg (roughly 3.3-4 kPa) in healthy adults, with globulins and other proteins providing additional, smaller contributions.

Clinical relevance includes the role of COP in maintaining intravascular volume and fluid balance. Reduced colloidosmotic pressure, often due to hypoalbuminemia from liver disease, nephrotic syndrome, or severe malnutrition, can lead to edema as fluid shifts into the interstitial space. Increased COP is less common but can occur in certain conditions. Routine measurement of COP is not common; management generally targets underlying protein loss, nutrition, and overall fluid status.