Chronic edema is a term used to describe a group of conditions characterized by swelling that has been persistent for greater than three months. It is caused by the accumulation of excess fluid within the interstitial space of the affected area(s), and may occur as a result of many disease processes. The terms chronic edema and lymphedema are often used interchangeably. This is because any form of edema results from some degree of lymphatic impairment or overload of the system– either because the lymphatic system is not working properly (primary or secondary), or there is simply too much fluid for a normal lymphatic system to process.
Chronic edema can occur due to damage of the normal lymphatic system during surgery, infection, injury or result from an underdeveloped lymphatic system (genetic abnormalities).
In the case of chronic venous disease, the poorly functioning veins results in pooling of blood in the legs and higher venous pressures. This leads to an overload of the lymphatic system, which may then lead to lymphatic failure and chronic edema (also called Phleblymphedema). See also, What is Lymphedema.
Lymphoedema Framework. Best Practice for the Management of Lymphoedema. International consensus. London: MEP Ltd, 2006.