Edema, general term for the accumulation of excess fluid in any body tissue, cavity, or organ, except bone. Accumulation in the pleural cavity is called pleural effusion; in the cranium, hydrocephalus; and in the abdominal cavity, ascites. Generalized edema is referred to as anasarca. Major causes are heart or kidney failure, low blood serum protein after starvation or liver failure, shock, and impaired return of blood from extremities. Treatment involves stimulating the kidneys to excrete excess fluid and the use of arterial tone reducers and digitalis for heart failure.