Edema (also oedema, dropsy, and hydropsy) (/ɨˈdimə/; Greek οἴδημα oídēma, "swelling")[1] is an abnormal accumulation of fluid in the interstitium, located beneath the skin and in the cavities of the body. Clinically, edema is manifest 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 edema.
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Cutaneous edema is referred to as "pitting" when, after pressure is applied to a small area, the indentation persists after the release of the pressure. Peripheral pitting edema, as shown in the illustration, is the more common type, resulting from water retention. It can be caused by systemic diseases, pregnancy in some women, either directly or as a result of heart failure, or local conditions such as varicose veins, thrombophlebitis, insect bites, and dermatitis.