Edema is the abnormal buildup of fluid in a part of the body, which can cause swelling and pain.

Some causes of edema include:

• Inactivity. Swelling of the ankles during a long airplane trip is an example of edema caused by inactivity.
• Diseases such as heart failure. If the left side of the heart is damaged, it can cause fluid to build up in the lungs (pulmonary edema).
• Blood clots that stop the flow of blood through a blood vessel. This causes blood to pool behind the clot.
• Infection. The body often fights an infection by increasing blood flow to the area, which can result in edema.

The treatment for edema depends on the cause.