The balance and regulation of fluid in the body is very complex. In short,
the cause of edema as simply defined as possible, is that tiny blood vessels in the body
(capillaries) leak fluid into the surrounding tissues. This excess fluid causes
the tissues to swell.
The cause of fluid leaking into the surrounding tissues may be the result of
several mechanisms, for example:
- too much force, or pressure inside the blood vessels;
- a force outside of the blood vessel causes the fluid to be drawn through
- the wall of the blood vessel is compromised and cannot maintain
Each of these three mechanisms may be associated with a variety of diseases
or conditions. Examples include the following.
- Pregnancy: Edema during
pregnancy may occur because
pregnant women have a
greater volume of fluid circulating in the body, and because they also retain
more fluid. A woman may also experience
- Medications: Edema may be caused by a variety of medications, for
example, steroids, calcium
channel blockers (CCBs), thiazolidinediones,
drugs (NSAIDs), estrogens, etc.).
- Liver disease and/or kidney disease:
Both of these organs are vital in maintaining
fluid balance in the body, and if severe disease is present in either of these
organ systems, edema can develop. Examples include:
cirrhosis of the liver,
chronic kidney disease,
and acute kidney failure.
- Venous insufficiency: This is a common condition in
which blood does not return to the heart efficiently from the peripheral areas of the body (for
example, the ankles,
legs, feet, hands), which results in edema. This typically results in edema in
- Heart failure: If the heart is weak and cannot pump blood efficiently,
blood will pool in particular areas of the body, which will cause fluid to leak
from the blood vessels into the surrounding tissues.
- If the right side of the heart is weak, pressure will build in the
peripheral tissues in the body (hands, ankles, feet, legs). This is referred to
as peripheral edema.
- If the left side of the heart is weak, pressure will
build in the lungs, causing pulmonary edema.
- Idiopathic edema: Accumulation of fluid in surrounding tissues with no
identifiable cause is referred to as idiopathic edema.
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