Edema occurs when tiny blood vessels in your body (capillaries) leak fluid. The fluid builds up in surrounding tissues, leading to swelling.

Mild cases of edema may result from:

  • Sitting or staying in one position for too long
  • Eating too much salty food
  • Premenstrual signs and symptoms
  • Pregnancy

Edema can be a side effect of some medications, including:

  • High blood pressure medications
  • Nonsteroidal anti-inflammatory drugs
  • Steroid drugs
  • Estrogens
  • Certain diabetes medications called thiazolidinediones

In some cases, however, edema may be a sign of a more serious underlying medical condition. Diseases and conditions that may cause edema include:

  • Congestive heart failure. When one or both of your heart's lower chambers lose their ability to pump blood effectively — as happens in congestive heart failure — the blood can back up in your legs, ankles and feet, causing edema. Heart failure can also cause swelling in your abdomen. Sometimes it can cause fluid to accumulate in your lungs (pulmonary edema), which can lead to shortness of breath.
  • Cirrhosis. Fluid may accumulate in your abdominal cavity (ascites) and in your legs as a result of liver damage (cirrhosis).
  • Kidney disease. When you have kidney disease, extra fluid and sodium in your circulation may cause edema. The edema associated with kidney disease usually occurs in your legs and around your eyes.
  • Kidney damage. Damage to the tiny, filtering blood vessels in your kidneys can result in nephrotic syndrome. In nephrotic syndrome, declining levels of protein (albumin) in your blood can lead to fluid accumulation and edema.
  • Weakness or damage to veins in your legs. Chronic venous insufficiency, in which the one-way valves in your leg veins are weakened or damaged, allows blood to pool in the leg veins and cause swelling. Abrupt onset of swelling in one leg accompanied by pain in your calf can be due to a clot in one of your leg veins. Seek medical help promptly.
  • Inadequate lymphatic system. Your body's lymphatic system helps clear excess fluid from tissues. If this system is damaged — for example, by cancer surgery — the lymph nodes and lymph vessels draining an area may not work correctly and edema results.
Sep. 19, 2014

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