Dropsy is a general term for an abnormal accumulation of fluid beneath the skin, or in one or more of the cavities of the body. It is due to one of three conditions: (a) weakening of the walls of the capillary vessels by injury, ill-health, impoverished blood, or poisons in the blood; (b) obstruction of the blood flow through the veins; (c) a watery condition of the blood, allowing fluid to escape through the capillary walls. Dropsy may also result from obstruction to the flow of lymph in the lymph channels.
Limited dropsy under the skin is called oedema, when widespread anasarca; dropsy in the abdomen is ascites; in the chest it is hydrothorax. Dropsy is not a disease, although this is a popular idea supported by the fact that at one time many deaths were recorded as due to dropsy without further statement of the cause.
Dropsy is found in people with a variety of disorders, for example heart disease which produces increased pressure in the veins due to defective pumping, and also an impure condition of the blood; Bright's disease, which causes watery and impure blood; and cirrhosis, tumours, and other diseases of the liver may, by interference with the circulation through it, cause dropsy, first of the abdomen and later of the lower limbs. Hunger oedema, due to diminution of the amount of protein in the blood as a result of starvation, is generalized in the body, but in the earlier stages is most marked in the feet and legs.