Oedema is the medical term for fluid retention in the body.
The build-up of fluid causes affected tissue to become swollen. The swelling can occur in one particular part of the body – for example, as the result of an injury – or it can be more general.
This is usually the case with oedema that occurs as a result of certain health conditions, such as heart failure or kidney failure.
As well as swelling or puffiness of the skin, oedema can also cause:
• skin discolouration
• areas of skin that temporarily hold the imprint of your finger when pressed (known as pitting oedema)
• aching, tender limbs
• stiff joints
• weight gain or weight loss
• raised blood pressure and pulse rate
Types of oedema
Oedema can occur anywhere in the body, but it's most common in the feet and ankles. This is known as peripheral oedema.
Other types of oedema include:
• cerebral oedema – affecting the brain
• pulmonary oedema – affecting the lungs
• macular oedema – affecting the eyes
Idiopathic oedema is a term used to describe cases of oedema where a cause can't be found.
What causes oedema?
It's normal to have some swelling in your legs at the end of the day, particularly if you've been sitting or standing for long periods.
Oedema is often a symptom of an underlying health condition. It can occur as a result of the following conditions or treatments:
• kidney disease
• heart failure
• chronic lung disease
• thyroid disease
• liver disease
• medication, such as corticosteroids or medicine for high blood pressure (hypertension)
• the contraceptive pill
Immobility and standing for long periods are the two most common causes of oedema in the legs.
Other possible causes include:
• a blood clot
• severe varicose veins
• a leg injury or leg surgery
• burns to the skin
Oedema usually clears up by itself. However, your GP may suggest some self-help measures to reduce fluid retention, such as:
• losing weight (if you're overweight)
• taking regular exercise, such as walking, swimming or cycling
• raising your legs three to four times a day to improve your circulation
• avoiding standing for long periods of time
If an underlying condition is causing the fluid imbalance, it should clear up after the condition has been diagnosed and treated.
Lymphoedema is swelling in the legs caused by a blockage in the lymphatic system, or an inherited condition, such as Milroy's disease, that causes an abnormality of the lymph vessels.
The lymphatic system consists of a series of lymph nodes (glands) connected by a network of vessels, similar to blood vessels.
Fluid surrounding body tissues usually drains into nearby lymph vessels so it can be transported back into the blood. However, if the lymph vessels are blocked, the fluid can't be reabsorbed and will build up in the tissue.
Unlike oedema, lymphoedema is a long-term condition that can cause discomfort, pain and a loss of mobility.
It can't be cured, but it can be controlled using a number of treatments, including compression stockings, skin care, lymphatic massage and elevation.