Edema

Edema is an accumulation of excess fluids in the spaces between the cells of tissues, know as interstitial space. It can be classified into two types: lymphatic edema, in which plasma proteins in the tissues stagnate owing to mechanical insufficiency of lymph drainage, and venous edema, which results from increased capillary pressure and venous obstruction.

When the lymphatic system is incompetent, obstructed, or surgically obliterated, proteins and their products accumulate in the tissue space. Edema occurs when there is an imbalance of the affected pressures across the capillary membrane or when there is obstruction to the venous or lymphatic flow. Thus, the tissue has abnormally large quantities of fluid in the intercellular spaces.

Localized edema:

is usually caused by venous or lymphatic obstruction or to increased vascular permeability as seen in post-traumatic edema. Localized edema tends to be limited to one area of the body, but it can be seen in bilateral extremities. This edema can be the result of trauma, infection, or obstruction.

Generalized edema:

is a systemic process that occurs with chronic illnesses such as advanced cardiac disease, kidney failure, or liver disease. These types of edema usually are apparent in both lower extremities, the groin, and abdominal areas, but some patients exhibit a more generalized appearance of "whole body edema."