Edema: Definition and Overview

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What Is Edema & What Causes It

What is edema?

Edema is an abnormal accumulation of fluid in various body tissues, causing swelling. The swelling may affect any of a number of body sites, such as the legs, ankles, and feet; the hands; the back or abdomen; and even the eyelids. Edema may be caused by a number of different medical conditions and can also be a side effect of certain drugs. Here are some possible causes:

    • Congestive heart failure may result in edema. To compensate for heart failure, in which the heart fails to circulate adequate amounts of blood, the kidneys retain sodium to help the body hold on to water and increase the volume of blood.


    • Deep vein thrombosis, the formation of a blood clot in a deep vein within the leg, can cause edema by damaging the valves within the veins that control normal blood flow. This type of edema most commonly makes the ankles swell but may also cause swelling in the calf or even the thigh.


    • Kidney diseases, such as diabetic nephropathy, may cause edema due to excess sodium and fluid retention.


  • Edema may be a side effect of certain drugs, including the oral diabetes drugs pioglitazone (brand name Actos) and rosiglitazone (Avandia). People sometimes experience mild edema when starting on insulin therapy, but this generally goes away within a few weeks.

If you experience any unusual swelling, be sure to contact your doctor. It may be the result of a medical condition you don’t know you have. Treating edema involves treating the underlying medical condition that is causing it or adjusting medication as necessary.

Originally Published May 22, 2006

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