What Is Edema? What Causes Edema?

Edema, is swelling caused by fluid retention - excess fluid is trapped in the body's tissues. In the UK/Ireland/Australasia and some other countries the word is spelled oedema. Swelling caused by edema commonly occurs in the hands, arms, ankles, legs and feet. It is usually linked to the venous or lymphatic systems. Edema was formerly known as dropsy or hydropsy.

Edema may be generalized or local. It can appear suddenly, but usually develops subtly - the patient may first gain weight, or wake up with puffy eyes. Many patients wait until symptoms are well advanced before seeking medical help.

The rest of this article refers mainly to generalized edema, unless otherwise specified.

According to Medilexicon's medical dictionary, edema is:

"1. An accumulation of an excessive amount of watery fluid in cells or intercellular tissues.
2. At the gross level, used to describe the physical sign commonly likened to swelling or increased girth that often accompanies the accumulation of fluid in a body part, most often a limb."

The English word "edema" comes from the Greek word oidema, meaning "a swelling tumor", which is derived from the Greek verb oidein meaning "to swell".

It is estimated that approximately 4.4 million people in USA have edema.

There are many types of edema. The most common ones are:

• Peripheral edema - in the feet (pedal edema), ankles, legs, hands and arms.


• Cerebral edema - in and around the brain (cerebral edema).


• Eye edema - in and around the eyes, e.g. macular edema, corneal edema, periorbital edema (puffiness around the eys. Macular edema is a serious complication of diabetic retinopathy. The CDC (Centers for Disease Control and Prevention) estimates that the number of cases of diabetic retinopathy will triple from 5.5 million in 2005 to 16 million in 2050.

What causes edema?

If the capillaries (tiny blood vessels) leak fluid into the surrounding tissue the area will start to swell. This could be due to capillary damage or increased pressure.

Leaking capillaries will cause the kidneys to accumulate higher than normal quantities of sodium (salt) and water in order to compensate for the capillary fluid loss. This results in more blood circulating in the body, which in turn causes even more capillary leakage into the surrounding tissue, which produces additional swelling - a vicious cycle.

Edema is most commonly caused by:

• Physical inactivity - edema is more prevalent among people who do not exercise at all, and walk very little.


• Standing or sitting still for long - if you stand or sit still for a long time there is a much higher chance of swelling.


• Genes - researchers in Spain identified the genes that cause blindness produced by corneal edema.


• Surgery - there is usually some swelling after a surgical procedure.


• High altitudes - especially when combined with physical exertion. Acute mountain sickness can lead to high altitude pulmonary edema or high altitude cerebral edema.


• Heat - especially when combined with physical exertion. During high temperatures the body is less efficient at removing fluid from tissues, especially around the ankles.


• Burns - the skin reacts to a burn by retaining fluid, causing localized swelling.


• Pregnancy - during pregnancy the woman releases hormones which encourage the body to retain fluids. Pregnant women tend to retain much more sodium and water than women who are not pregnant. When a woman is pregnant her face will typically swell, as will her hands, lower limbs and feet.
  
  When the woman is resting in a reclined position the enlarged uterus occasionally compresses the inferior vena cava, causing obstruction of both femoral veins, leading to edema.
  
  A pregnant woman's blood is hypercoaguble (clots more easily), raising the risk of deep venous thrombosis (DVT), a cause of edema. Eclampsia, which results from pregnancy-induced hypertension (high blood pressure), can also cause edema.


• Menstruation and pre-menstruation - hormone levels fluctuate during the menstrual cycle. During the days before menstrual bleeding there will be a reduction in the levels of the hormone progesterone, which may cause fluid retention.


• The contraceptive pill - any medication that includes estrogen can cause fluid retention. It is not uncommon for women to put on weight when they first go on the pill.


• Menopause - around the period of the menopause as well as after it, hormone fluctuations can cause fluid retention. Hormone replacement therapy after the menopause can also cause edema.


• Certain medications - such as vasodilators (drugs that open blood vessels), calcium channel blockers, NSAIDs (non-steroidal anti-inflammatory drugs), estrogens, several chemotherapy drugs, and some diabetes drugs, such as thiazolidinediones. Scientists in the University of Utah discovered why thiazolidinediones cause edema
.

• Excessive salt intake - this is especially the case for people who are susceptible to developing edema.


• Malnutrition and/or bad diet - dietitians say low consumption of thiamine (vitamin B1), as well as insufficient vitamins B6 and B5 may contribute toward fluid retention. Low levels of albumin levels may also play a part - low albumin levels can also be caused by kidney disease.

Edema can also be caused by the following diseases:

• Kidney disease/damage - patients with kidney disease may not be able to eliminate enough fluid and sodium from the blood. This results in more pressure on the blood vessels, which causes some of the liquid to leak out. Kidney disease patients with edema will generally have swelling around their legs and eyes.
  
  Damage to the capillaries in the kidneys (glomeruli) that filter waste and excess fluids from the blood can result in nephrotic syndrome. Among the many symptoms of nephrotic syndrome is an insufficient level of blood albumin, which leads to edema.


• Heart failure - this is when the heart cannot pump blood properly to all parts of the body. If one or both of the lower chambers of the heart lose the ability to pump blood effectively, the blood can accumulate in the limbs, causing edema.


• Chronic lung disease - this includes many lung diseases, such as asthma, chronic bronchitis, COPD, emphysema, pulmonary fibrosis and sarcoidosis. Some patients may experience an accumulation of fluids in the lungs - pulmonary edema.


• Liver disease - such as cirrhosis, which causes scarring of the liver. This affects liver function, which causes the secretion of hormones and fluid-regulating chemicals to change. People with cirrhosis of the liver also have increased pressure within the portal vein - a large vein that carries blood from the intestines, spleen and pancreas into the liver. The problems can lead to fluid retention in the legs and ascites (abdominal cavity).


• Diabetes - a patient with diabetes may have edema for several different reasons, including cardiovascular disease and its complications, acute renal failure, acute liver failure, protein losing enteropathy (disease of the intestine causing protein loss), and some medications. Diabetic macular edema is the swelling of the retina in diabetes.


• Allergies - some foods and insect bites may cause edema in susceptible people.


• Arthritis - people with arthritis most commonly have swelling in the ankles, feet, legs, and calves - peripheral edema. Arthritis may cause swelling for many reasons, for example, sporadic ankle swelling in rheumatoid arthritis is common and occurs mainly as a result of active inflammatory synovitis (inflammation of the synovial membrane, the lining of the joint).


• Thyroid disease - people with a disorder of the thyroid gland commonly experience edema.


• Brain tumor - a brain tumor will accumulate water around itself, especially as it builds new blood vessels.


• Head injury - a blow to the head may result in an accumulation of fluids in the brain or between the brain and the skull.

Edema in the leg is most commonly caused by:

• A blood clot - any blockage, such as a clot in one of the veins can impede the flow of blood. This causes an increase in pressure in the vein, which may result in leakage of fluids into the surrounding tissue, causing edema.


• Varicose veins - these often accompany symptoms of edema. Varicose veins usually occur because valves become damaged; static pressure increases, resulting in the bulging veins. The static pressure also increases the risk of leakage of fluids into the surrounding tissue.


• Infection/inflammation - the lymph nodes may swell in response to infection.


• A cyst/growth/tumor - edema can causes cysts, which can then cause more edema. Any lump can cause edema for a number of reasons. The lump may press against a vein causing a build-up of pressure in that vein, which may result in fluids leaking into surrounding tissue. The lymph nodes may react to a tumor and swell.


• Lymphedema - the lymphatic system helps get rid of excess fluid from tissues. If this system is damaged the lymph nodes and lymph vessels which continually drain an area may not work as they should, it could result in edema.
  
  If the damage is due to lymphedema it is called primary lymphedema, if it is caused by a disease or medical condition, such as an infection or cancer, it is caused secondary lymphedema.

What are the symptoms of edema?

Symptoms will mainly depend on the underlying cause. The following refer to generalized edema:

• Swelling of the skin.
• Skin may be stretched and shiny.
• The skin may retain a dimple after being pressed for about ten seconds.
• Puffiness of the ankles, face or eyes.
• Aching body parts.
• Stiff joints.
• Weight gain.
• Weight loss.
• Hand and neck veins are fuller.
• Raised pulse rate.
• Hypertension - raised blood pressure.
• Ascites - increased abdominal size.

What is the diagnosis of edema?

A GP (general practitioner, primary care physician) will want to determine what the underlying cause of the edema is. The patient will be asked questions about his/her:

• Medical history.
• Current state of health.
• How long the signs and symptoms have existed.
• How permanent or intermittent the signs and symptoms are.
• Whether the patient has had edema before.

The physician will also carry out a physical exam. If there are indications that there may be an underlying medical condition causing the edema the doctor may order some tests, these may include:

• A chest X-ray
• Blood tests
• Urine tests
• Liver function tests
• Heart function tests

What is the treatment for edema?

In order to treat the edema the doctor has to diagnose the condition that is causing it first.

• Diuretics
  
  These are drugs that raise the rate of urination, providing a means of forced dieresis. Diuresis is the increased production of urine by the kidney. There are several types of diuretics - they increase the excretion of water from the body in various different ways. Diuretics are not suitable if the patient is pregnant, or has chronic venous insufficiency (weakened valves in the veins of the legs).
  
  Many medications appear to cause pedal edema (foot edema), especially estrogens, vasodilators, NSAIDS, and calcium channel blockers. Most edemas caused by medications are the types that are caused by high blood pressure in the capillaries. For these patients diuretics are not an effective treatment. Physicians report that angiotensin-converting enzyme inhibitors and angiotensin-receptor blockers give better results.


• Antiangiogenesis therapy (controlling blood vessel growth)
  
  The beneficial effects of anti-angiogenesis drugs in the treatment of the glioblastomas (deadly brain tumors) appear to result primarily from reduction of edema, researchers at the Massachusetts General Hospital reported.


• Oxygen therapy
  
  Oxygen delivered through the nose may improve poor vision caused by diabetic macular edema, say researchers at Johns Hopkins.

A good GP will also recommend the following self-care techniques which may help resolve the fluid retention problem:

• Cut down salt consumption.


• If the patient is overweight, to lose weight.


• Do regular exercise.


• Raise the legs several times per day to improve circulation.


• Wear supporting stockings.


• Not to sit/stand still for too long.


• Get up and walk about regularly when travelling by car, train, boat or plane.


• Avoid extremes of temperature, such as hot baths, showers, and saunas. Dress warmly if it is cold.


• Massage - if the affected area is stroked firmly in the direction of the heart it may help move the fluid. It is important that the hand movements do not cause pain. A qualified masseuse or physical therapist will know how to do this more effectively.

What are the complications of edema?

Edema is usually caused by an underlying disease or condition. If that condition is not treated, the health consequences could be serious. Untreated edema can cause:

• Painful swelling. The pain can gradually get worse.


• Walking difficulty.


• Stiffness.


• Awkward gait.


• Skin can become stretched, itchy and bothersome.


• The swollen area is more likely to become infected.


• Scarring may occur between the layers of tissue.


• Poor blood circulation.


• Arteries, veins, and joints may lose their elasticity.


• Ulcerations of the skin.