Edema

Definition

Edema is the medical term for swelling. It is an abnormal retention of fluid in body tissue.

Description

Edema that is visible and localized often accompanies a soft-tissue injury, a sprain, or a fracture. However, it is also a component of generalized retention of fluid such as occurs in congestive heart failure (CHF). By weight, 60% of the human body is composed of water. In a remarkable process that is, under normal circumstances, a nearly perfect balance, water is exchanged between the blood and the tissues. As it circulates blood through the body, the pressure from the heart presses water out of capillaries and into body tissues. Osmotic (water-drawing) properties of certain blood proteins cause this process to reverse and fluid to be reabsorbed from the tissues back into the capillaries. To maintain equilibrium, the kidneys draw off excess fluid and salt, which are then excreted as part of the urine. When fluid is not released from the tissues, the result is edema.

Causes and symptoms

The causes and severity of edema cover a wide spectrum, including:

mild edema that accompanies female hormone imbalance during the menstrual cycle
allergies in which the chemical histamine is released by the immune system, resulting in fluid leaking into the tissues, which creates swelling
injuries that do damage to capillaries, causing fluids to seep out into the tissue and not be reabsorbed by the damaged capillaries
hormonal imbalance caused by taking certain hormonal medications such as corticosteroids, high estrogen contraceptives, or androgens (male hormones)
beriberi (vitamin B₁ deficiency) and dietary protein deficiency, often found with malnutrition
the venous congestion that accompanies cirrhosis of the liver and eventually decreases osmotic pressure
kidney failure, which eventually allows salts and water to be retained in the tissues rather than being excreted
nephritic syndrome, a condition in which large amounts of blood protein are lost and the blood loses its ability to draw fluid back out of the tissues
congestive heart failure, a common condition, especially in the elderly, in which the heart functions less efficiently due to coronary artery disease, high blood pressure, or congenital or disease-caused abnormality in the heart

Other than traumatic injuries or allergic reactions, swelling typically develops quite slowly and often goes unnoticed at its onset. It is estimated that fluid in the body can increase by 15% without being visible. Frequently it is manifested at that point only by an increase in weight. When edema does become apparent, it is usually found in the lower part of the body, in the feet, ankles, legs, and lower back. A finger pressed into edematous skin will leave an imprint that slowly disappears as the fluid again refills that tissue.

Severe edematous conditions can cause fluid to gather in body cavities. Ascites, common with cirrhosis of the liver, is characterized by large amounts of fluid amassing in the peritoneal cavity of the abdomen. When liquid fills the pleural cavity adjacent to the lungs, it is termed pleural effusion; the liquid presses upon the lungs, causing difficulty in breathing. Pulmonary edema, which occurs when air sacs in the lungs become waterlogged, also causes respiratory complications.

Diagnosis

Diagnosis of the cause of edema is based upon physical examination and laboratory testing, plus a complete medical history. For patients with a history of CHF or kidney disease, weights are frequently taken to watch for fluid retention.

Treatment

The simple act of elevating the legs sometimes will reduce edema. However, the primary means of treating edema is in determining the cause of the fluid retention and attempting to remedy that. Giving antihypertensive drugs to people with high blood pressure will sometimes eliminate the edema. Often, though, the underlying cause of the edema is not easily remedied, such as in the case of CHF. Treatment of CHF may include:

limiting the salt in the diet
taking diuretics, medications that stimulate the kidneys to excrete the excess salt and water
taking angiotensin-converting enzyme inhibitors (ACE inhibitors) and vasodilator drugs, which cause blood vessels to expand and allow blood to flow easier, decreasing the work required of the heart
taking beta blockers, which improve the functioning of the left ventricle of the heart
taking digitalis, a drug that expands the ability of the heart to pump blood through the body
having surgery to replace abnormal heart valves; in extreme cases, heart transplant may be needed

Prognosis

The outcome for edema depends heavily upon its cause. The best outlook for the relief of edema is when the underlying condition is treatable.

Health care team roles

Edema is most often noticed by either the patient, by a primary care physician or nurse-practitioner during a routine examination, or by nursing staff caring for the patient in a health care facility or at home.

Both registered nurses (RNs) and licensed practical nurses (LPNs) must complete a prescribed course in nursing and pass a state examination. RNs typically have a degree in nursing. Good nursing care of the patient with edema will include observation, elevating the legs if the lower extremities are swollen, monitoring vital signs and weights, and providing education about the cause of the edema.

Clinical laboratory scientists have specialized training and must pass a state examination. They draw blood samples or do the necessary tests on fluids withdrawn from fluid-filled body cavities.

Radiologic technologists have specialized training and must pass a state examination. They take x rays and other tests to visualize and monitor the course of disease processes that contribute to the edema.

KEY TERMS

Capillaries—The term for any of the vessels that carry blood between the smallest arteries, or arterioles, and the smallest veins, venules.

Congestive heart failure—A condition in which the heart cannot circulate enough blood to meet the needs of the body.

Corticosteroids—A group of medications that have similar properties to the corticosteroid hormones that the adrenal glands produce naturally.

Fracture—A partial break in a bone.

Histamine—A chemical present in cells that is released during an allergic reaction and that causes the symptoms of inflammation, including swelling.

Osmosis—The passage of a fluid such as water through a sieve-like tissue called a semipermeable membrane from a less concentrated, or weaker, solution to a more concentrated, or stronger one.

Soft-tissue injury—Damage to tissue that encloses bones or joints, such as muscles, tendons, or ligaments.

Sprain—The tearing or stretching of ligaments holding bone ends together in a joint, usually caused by sudden, violent pulling.

Prevention

Prevention of edema is dependent upon treatment of the basic reason for the edema. Losing weight, stopping smoking, and reducing stress can all aid in reducing blood pressure. Proper nutrition can help to maintain a healthy circulatory system.