Oedema is an accumulation of interstitial fluid. The volume of fluid in the interstitial space is normally kept constant at around 20% of body weight.1 Several factors control the direction of flow of interstitial fluid including hydrostatic pressure, oncotic pressure, endothelial integrity, and lymphatic systems.2 These components are described by Starling’s law where fluid movement across capillaries is proportional to capillary permeability, trans-capillary hydrostatic pressure differences, and trans-capillary oncotic pressure differences.3
This is a companion discussion topic for the original article at https://patient.info/doctor/peripheral-oedema