Fluid distribution and edema Edema, also spelled œdema, is an abnormal accumulation of fluid in the interstitium, located beneath the skin and in the cavities of the body, which can cause severe pain. Clinically, edema manifests as swelling. The amount of interstitial fluid is determined by the balance of fluid homeostasis; and the increased secretion of fluid into the interstitium, or the impaired removal of the fluid, can cause the condition. The word is from Greek οἴδημα oídēma meaning "swelling".