Heart Failure Health Center

Edema Overview

Edema is the medical term for swelling. Body parts swell from injury or inflammation. It can affect a small area or the entire body. Medications, infections, pregnancy, and many other medical problems can cause edema.

Edema happens when your small blood vessels become "leaky" and release fluid into nearby tissues. That extra fluid builds up, which makes the tissue swell.

Causes of Edema

Things like a twisted ankle, a bee sting, or a skin infection will cause edema. In some cases, like an infection, this may be helpful. More fluid from your blood vessels puts more infection-fighting white blood cells in the swollen area.

Edema can also come from other conditions or from when the balance of substances in your blood is off. For example:

Low albumin: Your doctor may call this hypoalbuminemia. Albumin and other proteins in the blood act like sponges to keep fluid in your blood vessels. Low albumin may contribute to edema, but it’s not usually the only cause.

Allergic reactions: Edema is a part of most allergic reactions. In response to the allergen, nearby blood vessels leak fluid into the affected area.

Obstruction of flow: If drainage of fluid from a part of your body is blocked, fluid can back up. A blood clot in the deep veins of your leg can cause leg edema. A tumor blocking the flow of blood or another fluid called lymph can cause edema.

Critical illness: Burns, life-threatening infections, or other critical illnesses can cause a reaction that allows fluid to leak into tissues almost everywhere. This can cause edema all over your body.

Heart disease ( congestive heart failure ): When the heart weakens and pumps blood less effectively, fluid can slowly build up, creating leg edema. If fluid buildup occurs quickly, fluid in the lungs, known as pulmonary edema, can develop. If your heart failure is on the right side of your heart, edema can develop in the abdomen, as well.

Liver disease: Severe liver disease (such as cirrhosis) causes you to retain fluid. Cirrhosis also leads to low levels of albumin and other proteins in your blood. Fluid leaks into the abdomen and can also cause leg edema.