Generalized edema refers to fluid accumulation that affects the whole body rather than particular organs or body areas.
Some examples of organ-specific edema include:
- Cerebral edema (involving the brain)
- Pulmonary edema (involving the lungs)
- Macular edema (involving the eyes)
In generalized edema, fluid collects in the interstitial tissues, either because more fluid is being secreted or because removal of the fluid is failing.
The effects of gravity mean the swelling is often most marked in the lower body. For example, if a person is ambulant or able to walk, the fluid mainly gathers around the feet and ankles, while individuals who are bedridden tend to have more widespread edema.
Generalized edema is often a feature of heart failure, when the hydrostatic pressure in the blood vessels rises. In conditions such as nephrotic syndrome and liver failure, the oncotic pressure often falls. These underlying conditions can cause a generalized edema that affects peripheral tissues and several organs. For instance, heart failure can cause pulmonary edema, ascites (fluid collection around the abdominal organs), pleural effusions (fluid in the lungs) as well as peripheral edema (swelling in the lower limbs).
Edema due to nephrotic syndrome is often caused by alterations in the capillary structure of the glomeruli, changes that occur to some extent in most other bodily tissues.
Several medications may also cause generalized edema, such as the blood pressure lowering calcium channel blockers and vasodilators.