Edema is an excess of fluid in your body tissues or cavities. Normally the circulatory system maintains a balance of fluid by transporting it in and out of blood vessels. Edema is caused by too much fluid moving from the blood vessels into the tissues, or not enough fluid moving from the tissues back into the blood vessels. This fluid imbalance can cause swelling in one or more parts of the body. Edema can have many causes, including imbobility, certain medications, overexposure to heat, too much sodium, and pregnancy. Certain diseases such as heart or kidney disease, arthritis or cancer can also bring on edema. For more information about edema, contact a healthcare provider.