DROPSY, the name given to a collection of serous fluid in all or any of the cavities of the body, or in the meshes of its tissues. Dropsy of the subcutaneous connective tissue is termed oedema when it is localized and limited in extent ; when diffuse it is termed anasarca; the term oedema is also applied to dropsies of some of the internal organs, notably the lungs. Hydrocephalus signifies an accumulation of fluid within the ventricles of the brain or in the arachnoid cavity; hydrothorax, a collection in the pleural cavities; hydropericardium, in the pericardium ; ascites, in the peritoneum.
Dropsy (excluding "epidemic dropsy," for which see below) is a symptom and not a specific disease, being the exaggeration of a normal condition. Fluid, known as lymph, is continually passing through the capillary walls into the tissues, and in health this is removed as fast as it is exuded, in one or more of three ways ; part is used in the nutrition of the tissues, part is returned to the general circulation by the veins, and part by the lymphatics. Any accumu lation constitutes dropsy and is a sign of disease, though not a disease in itself. The serous effusions due to inflammation are not included under the term dropsy. A dropsical fluid varies consider ably in composition according to its position in the body, but only slightly according to the disease which has given rise to it. Its specific gravity ranges betwen r,008 and r ,o i 8 ; the mineral salts present are the same in amount and kind as those of blood and do not vary with the position of the exudation. The quantity of albumin, however, depends much on the position of the fluid, and slightly on the underlying disease. In oedema the fluid contains only traces, whereas a pleural or peritoneal effusion is always highly albuminous. Also an effusion due to heart disease contains more albumin than one due to kidney disease. In appearance the fluid may be colourless, greenish or reddish from the presence of blood pigment, or yellowish from the presence of bile pigment ; trans parent or opalescent or milky from the presence of fatty matter derived from the chyle.
The simplest cause of dropsy is purely mechanical, blood pres sure being raised beyond a certain point owing to venous obstruc tion. This may be due to thrombosis of a vein as in phlegmasia dolens (white leg ), retardation of venous circulation as in varicose veins, or obstruction of a vein due to the pressure of an aneurism or tumour. Cardiac and renal dropsy are more complicated in origin, but cardiac dropsy is probably due to diminished absorption, and renal dropsy, when unassociated with heart failure, to in creased exudation. But the starting-point of acute renal dropsy, of the dropsy sometimes occurring in diabetes, and that of chloro sis is the toxic condition of the blood. For accounts of the various local dropsies see HYDROCEPHALUS ; ASCITES ; LIVER; etc. General dropsy, or dropsy which depends on causes acting on the system at large, is due chiefly to diseases of the heart, kidneys or lungs, occasionally to lardaceous disease, more rarely still to diabetes or one of the anaemias.
The natural tendency of all heart diseases is to transfer the blood pressure from the arteries to the veins, and, so soon as this has reached a sufficient degree, dropsy in the form of local oedema begins to appear at whatever may be the most dependent part of the body—the instep and ankle in the upright position, the lower part of the back or the lungs if the patient be in bed—and this tends gradually to increase till all the cavities of the body are in vaded by the serous accumulation. The diseases of the lungs which produce dropsy are those which obstruct the passage of the blood through them, such as emphysema and fibrosis, and thus act pre cisely like disease of the heart in transferring the blood pressure from the arteries to the veins, inducing dropsy in exactly a similar manner. The dropsy of renal disease is dependent for the most part on an excess of exudation, due largely to an increase of arter ial and cardiac tension. This in its turn produces arterial thicken ing and cardiac hypertrophy, which, if the case be sufficiently pro longed, brings about a natural removal of the fluid. In kidney cases, in the absence of cardiac disease, the dropsy appears first about the loose cellular tissue surrounding the eyes.
For the treatment of dropsy the reader is referred to the articles on the diseases of which it is a symptom. Briefly, tapping of the abdomen or puncture of the legs are resorted to in severe cases. Dehydration by diet may be valuable when the dropsy is other than renal. And there is the routine treatment by drugs, purgative, diaphoretic and diuretic as the symptoms of the case may demand.
Differing from the preceding is epidemic dropsy, the first re corded outbreak of which occurred in Calcutta in the year 1877. It disappeared during the hot weather of the following year, only to recur over a wider area in the cold months of r878 to 1879, and once again in the cold of 1879 to r 880. Since then only isolated cases have been recorded in the immediate neighbourhood of Cal cutta, though epidemics have broken out in other places. At the end of 1902 an outbreak occurred in the Barisal gaol, Bengal, in which nearly one-third of the cases ended fatally. Dropsy was an invariable feature, and was either the first symptom or occurred early. The lower limbs were first affected, trunk and upper limbs later in severe cases, the face very rarely. It was accompanied by pyrexia, gastro-enteritis, deep-seated pains in limbs and body, and burning and pricking of the skin. Various rashes appeared early in the attack, while eczema, desquamation and even ulceration supervened later. Anaemia was very marked, giving rise in Mauri tius to the name of acute anaemic dropsy. The, duration of the disease was very variable, the limits being three weeks and three months. Death was often sudden, resulting chiefly from cardiac and respiratory complications. Probably it is a vitamin-deficiency disease akin to beriberi.