The historical diagnosis of dropsy – which is now obsolete – indicated simply an abnormal accumulation of fluid; the word derives from the Greek hydrops (water). Alternative or supplementary terms included hydrothorax (fluid in the chest cavity), ascites (which still indicates excess free fluid in the abdominal cavity), anasarca (still used to describe generalized edema throughout the body), hydrocephalus (used until the nineteenth century to indicate excess fluid within the skull), and ovarian dropsy (large ovarian cysts filled with fluid). Edema was often a synonym for dropsy, but it now has additional connotations, and pulmonary edema has been differentiated from hydrothorax. Since the mid-nineteenth century, dropsy has been recognized as a sign of underlying disease of the heart, liver, or kidneys, or of malnutrition. Untreated dropsy was, eventually, always fatal.

Etiology and Epidemiology

The major underlying causes of dropsy are congestive heart failure, liver failure, kidney failure, and malnutrition. Because they were not clearly differentiated before the nineteenth century, a historical diagnosis of dropsy cannot be taken to indicate any one of these alone in the absence of unequivocal supporting evidence, as from an autopsy. However, heart failure was probably the most frequent of the four.

The etiologies of dropsy can be explained most conveniently in terms of fluid balance. One principal force in the maintenance of normal fluid balance is the hydrostatic (or hydraulic) pressure within capillaries. The other major force is oncotic pressure, the normal tendency for sodium or large particles (e.g., proteins) in capillary blood to draw water out of tissues, tissues, much as salt draws water to the cut surface of a raw potato.