Edema: (Pitting and Non-Pitting Edema) Causes, Diagnosis & Symptoms
(Pitting and Non-Pitting Edema) Causes, Diagnosis & Symptoms
What is edema?
Edema is observable swelling from fluid accumulation in body tissues. Edema most commonly occurs in the feet and legs, where it is referred to as peripheral edema. The swelling is the result of the accumulation of excess fluid under the skin in the spaces within the tissues. All tissues of the body are made up of cells and connective tissues that hold the cells together. This connective tissue around the cells and blood vessels is known as the interstitium. Most of the body's fluids that are found outside of the cells are normally stored in two spaces; the blood vessels (as the "liquid" or serum portion of your blood) and the interstitial spaces (not within the cells). In various diseases, excess fluid can accumulate in either one or both of these compartments.
The body's organs have interstitial spaces where fluid can accumulate. An accumulation of fluid in the interstitial air spaces (alveoli) in the lungs occurs in a disorder called pulmonary edema. In addition, excess fluid sometimes collects in what is called the third space, which includes cavities in the abdomen (abdominal or peritoneal cavity - called "ascites") or in the chest (lung or pleural cavity - called "pleural effusion"). Anasarca refers to the severe, widespread accumulation of fluid in the all of the tissues and cavities of the body at the same time.
What is pitting edema and how does it differ from non-pitting edema?
Pitting edema can be demonstrated by applying pressure to the swollen area by depressing the skin with a finger. If the pressing causes an indentation that persists for some time after the release of the pressure, the edema is referred to as pitting edema. Any form of pressure, such as from the elastic in socks, can induce pitting with this type of edema.
In non-pitting edema, which usually affects the legs or arms, pressure that is applied to the skin does not result in a persistent indentation. Non-pitting edema can occur in certain disorders of the lymphatic system such as lymphedema, which is a disturbance of the lymphatic circulation that may occur after a mastectomy, lymph node surgery, or congenitally. Another cause of non-pitting edema of the legs is called pretibial myxedema, which is a swelling over the shin that occurs in some patients with hyperthyroidism. Non-pitting edema of the legs is difficult to treat. Diuretic medications are generally not effective, although elevation of the legs periodically during the day and compressive devices may reduce the swelling.
The focus of the rest of this article is on pitting edema, as it is by far the most common form of edema.
What causes pitting edema?
Edema is caused by either systemic diseases, that is, diseases that affect the various organ systems of the body, or by local conditions involving just the affected extremities. The most common systemic diseases associated with edema involve the heart, liver, and kidneys. In these diseases, edema occurs primarily because of the body's retention of too much salt (sodium chloride). The excess salt causes the body to retain water. This water then leaks into the interstitial tissue spaces, where it appears as edema.
The most common local conditions that cause edema are varicose veins and thrombophlebitis (inflammation of the veins) of the deep veins of the legs. These conditions can cause inadequate pumping of the blood by the veins (venous insufficiency). The resulting increased back-pressure in the veins forces fluid stay in the extremities (especially the ankles and feet). The excess fluid then leaks into the interstitial tissue spaces, causing edema.
Swelling of the foot, ankle and leg can be severe enough to leave an indentation, or "pit," when you press on the area. This swelling (edema) is the result of excessive fluid in your tissues — often caused by congestive heart failure or blockage in a leg vein.
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 loses its ability to pump blood effectively — as happens in congestive heart failure — the blood can back up in your legs, ankles and feet, causing edema.
This disease causes scarring of your liver, which interferes with liver function, causing changes in the hormones and chemicals that regulate fluids in your body, as well as increasing pressure within the large blood vessel (portal vein) that carries blood from your intestine, spleen and pancreas into your liver. These problems can result in fluid accumulating in your legs and your abdominal cavity (ascites).
• Kidney disease.
When you have kidney disease, your kidneys may not be able to eliminate enough fluid and sodium from your blood. The extra fluid and sodium increases pressure in your blood vessels, causing edema. Edema associated with kidney disease usually occurs in your legs and around your eyes.
• Kidney damage.
Damage to the tiny blood vessels in your kidneys (glomeruli) that filter waste and excess water from your blood can result in nephrotic syndrome. One result of nephrotic syndrome is low levels of protein (albumin) in your blood, which can lead to fluid accumulation and edema.
Weakness or damage to veins in your legs. Chronic venous insufficiency (CVI) is a condition in which the veins in your legs are weakened or damaged and can't pump enough blood back to your heart. The remaining blood increases pressure in the veins, causing swelling.
• Inadequate lymphatic system.
Your body's lymphatic system helps clear excess fluid from tissues. If this system is damaged — either due to lymphedema that occurs on its own (primary lymphedema) or because of a disease or medical condition, such as cancer or an infection (secondary lymphedema) — the lymph nodes and lymph vessels draining an area may not work correctly and edema results.
Edema At A Glance
• Edema is a swelling, usually of the legs, due to the accumulation of excessive fluid in the tissues.
• The edema that occurs in diseases of the heart, liver, and kidneys is mainly caused by salt retention, which holds the excess fluid in the body.
• In certain liver and kidney diseases, low levels of albumin in the blood can contribute to fluid retention.
• Heart failure, cirrhosis of the liver, and a kidney disease called nephrotic syndrome are the most common systemic diseases that cause edema.
• Excess fluid that accumulates in the lungs is called pulmonary edema.
• Excess fluid that accumulates in the abdominal cavity is called ascites.
• Edema of unknown cause occurs primarily in women.
• Varicose veins or thrombophlebitis (a blood clot in an inflamed vein) of the deep veins in the legs causes edema that is localized to the legs.
• Therapy for edema consists of treating the underlying conditions, restricting salt intake, and often using diuretics (medicines to induce urination).
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