edema

DEFINITION — Edema means swelling in the small spaces that surround the body tissues and organs. Edema can occur nearly anywhere in the body. The location of the edema will depend, in part, on the underlying cause. Some of the most common sites are:

* Lungs (also called pulmonary edema)
* Abdomen (also called ascites)
* Extremities such as the lower legs (also called peripheral edema)

Pulmonary edema can be life-threatening. In comparison, ascites and peripheral edema can produce some discomfort and cosmetic concerns, but are generally not serious although the underlying cause of edema may be.

SYMPTOMS — Symptoms of edema depend upon the cause, but may include:

* Swelling or puffiness of the skin, causing it to appear stretched and shiny. This is typically seen in the lower legs (called peripheral edema) or lower back (called sacral edema, frequently seen in those who have been in bed for long periods). Swelling is often worst after sitting or standing for a period of time (due to gravity), and may be worst at the end of the day. Pushing on the swollen area for a few seconds will leave a dimple in the skin.

* Increased size of the abdomen (with ascites)

* Shortness of breath or difficulty breathing (with pulmonary edema)

CAUSES — In most cases, the process of edema formation begins when fluid leaks from the body's smallest blood vessels, called capillaries, into the surrounding tissues. The leakage can occur because of changes in pressure in the capillaries, weakening of the capillary wall from disease, or other factors.

Usually, the leakage itself is not enough to cause noticeable edema. However, when the body senses that fluid is being lost from the capillaries, it signals the kidneys to hold on to sodium and water. This results in an increase in the volume of fluid circulating in the blood vessels, which, in turn, leads to additional leakage of fluid from the capillaries. It is typically at this point that edema can be seen.

CONDITIONS ASSOCIATED WITH EDEMA — A number of different problems can cause edema. Some of the most common are unrelated to any specific disease. For example, damage to the veins in the legs (venous insufficiency) can cause abnormal pooling or clotting of blood in these vessels, leading to edema. Pregnancy, drug effects, and problems with drainage in the lymphatic system can also cause peripheral edema. Diseases commonly associated with edema include kidney disease, heart failure, and cirrhosis of the liver.

Venous insufficiency — A common cause of peripheral edema in clinical practice is venous insufficiency, one cause of which is a syndrome that may occur after an episode of venous blood clots (called deep vein thrombosis). In this case, the edema is usually limited to the lower extremities (feet or ankles) and may affect only one side (the left or right); other conditions that cause edema usually cause swelling of both extremities.

Pregnancy — Pregnant women retain a significant amount of sodium and water. Some of this excess fluid is required by the fetus and placenta. Edema of the hands, feet, and face is commonly seen.

Premenstrual syndrome — Edema that appears in a cyclic pattern (usually once per month) may occur due to premenstrual syndrome (PMS). Diuretics are of no benefit for edema related to PMS. (See "Patient information: Premenstrual syndrome (PMS) and premenstrual dysphoric disorder (PMDD)").

Drugs — Edema can be a side effect of a wide variety of medications.

Kidney disease — The edema of kidney disease causes swelling in the legs and around the eyes. It is caused by an increase in pressure in the blood vessels; this occurs when the kidneys excrete an insufficient amount of sodium and fluid. The extra fluid increases pressure on the blood vessel walls, which allows fluids to move from inside the blood vessel to the space around the vessel. Low levels of protein (albumin) in the blood may also contribute to the movement of fluid from the capillaries.

Heart failure — In heart failure, also called congestive heart failure, the heart is weakened and its pumping action is impaired. It can affect the right heart chambers, which receive blood from the body and pump it to the lungs to be filled with oxygen; or it can affect the left heart chambers, which pump oxygenated blood to the rest of the body. (See "Patient information: Heart failure causes, symptoms, and diagnosis").

Heart failure develops as a result of other conditions that damage the heart. These include heart attacks due to coronary heart disease, diseases of the heart valves, and hypertension (high blood pressure).

In right heart failure, pressure builds in the right chambers because they fail to pump blood efficiently. The pressure is reflected back to the blood vessels in the body that lead to the right chambers, frequently causing peripheral edema and, sometimes, ascites. The patient therefore notices swelling in the legs and abdomen, as well as other symptoms.

In left heart failure, pressure builds in the left chambers because they are failing to pump blood efficiently. The increased pressure affects the large blood vessels that connect the left side of the heart with the lungs. This causes edema in the lungs, or pulmonary edema, causing shortness of breath.

Cirrhosis — With cirrhosis, congestion in the liver leads to an increase in pressure within the blood vessels in the liver and subsequently, in the blood vessels leading into the liver, causing ascites. The patient may have pronounced swelling in the abdomen, as well as edema in the feet or, if the patient is lying down most of the day, swelling in the lower back (also called sacral edema). (See "Patient information: Cirrhosis").

DIAGNOSING THE CAUSE — A healthcare provider may use a number of different tools to determine the most likely cause for edema. For example, close examination of the legs and veins in the neck provide valuable clues. By listening to the lungs through a stethoscope or viewing the lungs on x-ray, providers can detect the presence of fluid, which indicates pulmonary edema. Blood and urine tests give information about possible kidney or liver disease.

TREATMENT — Treatment of edema is directed at the underlying cause; this may be done by removing the excess fluid with diuretics, elevating the legs, or using compression stockings.

Pulmonary edema is life-threatening and requires immediate treatment. Fluid in the lungs interferes with the transfer of oxygen from the lungs to the bloodstream. Pulmonary edema is treated according to its cause, and commonly requires supplemental oxygen, mechanical ventilation (a respirator forces air into the lungs), and several medications.

Other forms of edema can be treated more slowly since they are of less danger to the patient. Slow removal is recommended for patients with cirrhosis (liver disease) since rapidly changing fluid levels can cause serious illness.

Diuretics — Diuretics cause the kidneys to increase their excretion of water and sodium, reducing fluid volume throughout the body. Diuretics must be used carefully as fluid removal decreases the blood volume. In some patients, this can result in a decrease in blood pressure.

There are several types of diuretics, and not all types are used to treat edema; the two primary types used for edema are loop diuretics (eg, furosemide (Lasix®) and potassium sparing diuretics (spironolactone)).

Although diuretics are beneficial in many types of edema, they are not appropriate in every case. In particular, diuretics are generally not recommended for venous insufficiency or for edema caused by pregnancy, where fluid retention is generally normal.

Side effects — Side effects of loop and potassium sparing diuretics are uncommon when taken at the recommended doses. Many patients must empty their bladder more frequently for several hours after taking their diuretic. Although some symptoms may result from the loss of sodium and potassium, most patients tolerate diuretics very well.

Body positioning — Leg, ankle, and foot edema can be improved by elevating the legs above heart level for 30 minutes three or four times per day. Leg elevation alone may be sufficient therapy for patients with mild venous insufficiency, but is usually not adequate for more severe cases. In addition, it may not be practical for those who work to elevate their legs several times per day.

Compression stockings — Leg edema can also be prevented and treated with the use of compression stockings. Many types are available, including knee-high, thigh-high, and pantyhose. Knee-high stockings are sufficient for most patients; thigh-high stockings are less desirable because they tend to provide too much pressure behind the knees, reducing blood flow in the veins and causing discomfort.

Compression stockings that have varying degrees of pressure are best; the greatest pressure is applied at the ankle. The pressure should gradually decrease up to the knee. The white "antiembolism" stockings commonly given to patients in the hospital do not apply enough pressure at the ankle and are not adequate treatment for venous insufficiency.

Proper measurement and fitting of the stockings are important for the patient's comfort and safety. The following tips may also be helpful:

* Washing new compression stockings before wearing will reduce some of the initial stiffness and difficulty in putting them on.

* The stockings should be put on as early as possible in the morning when edema is minimal.

* Patients should lean against a firm back support (not on the bed) while putting on the stockings.

* Knee-high stockings can be put on by turning the leg portion of the stocking inside-out down to the heel. With the stocking stretched, the foot is slipped in while pulling the stocking firmly onto the foot by its folded edge. As the stocking is pulled on by the edge, it will turn right-side out and can be gently worked up the leg. Some manufacturers recommend wearing rubber gloves to slide the stocking up the leg rather than grasping and pulling the edge of the stocking.

* Heavy compression stockings may go on more easily if a light silk hose is worn under the compression garment, or if talcum powder is first applied to the foot and leg. Some patients do not have the strength or mobility to pull on compression stockings. Stockings are now available with a zippered back or velcro attachment.

WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of informati