Oedema describes swelling caused by fluid build-up in a tissue or organ. It commonly affects a specific area such as joints, hands, feet, ankles, the face or mouth, or internal organs. In severe cases, it can become widespread with generalised fluid retention called anasarca.^1,2,3,4,5

Excess fluid passing out of capillary walls can accumulate in the interstitial space between cells or within cells. The increased diffusion distance for oxygen and other nutrients this causes impairs cellular metabolism and removal of metabolic byproducts from the tissue. A more serious consequence is impaired gaseous exchange in the lungs.^3,6

Swelling in muscles and around joints can restrict movement, and pressure buildup can also impede processes involved in organ function such as in the kidneys or brain.⁶