Starling’s Bargain: The Physics of Capillary Fluid Exchange and Edema

This episode examines how microvascular fluid balance is governed by the equilibrium between hydrostatic and oncotic pressures across semipermeable capillary membranes. It explores the physiological variables—transcapillary pressure gradients (\Delta P), oncotic gradients (\Delta \pi), and the endothelial reflection coefficient (\sigma)—that dictate fluid filtration into tissue spaces. Finally, it demonstrates how distinct pathophysiological insults, such as hypoproteinemia and elevated venous pressure, converge on the shared clinical endpoint of edema.