In the harmless form, almost every one of us has ever had an edema, for example, swollen eyelids in the morning, too copious consumption of alcohol, swollen feet in the summer or the swelling after an insect bite. However, edema can be a symptom of serious illness.
Edema ("dropsy") is the accumulation of water from the vascular system in the intermediate tissue, usually connective tissue. In the affected area there is a mostly painless swelling. Typical: If you press your finger on the swelling, a dent remains, which gradually regresses.
Edema is not a disease of its own, but symptoms of already existing underlying diseases. They may be isolated, but also occur throughout the body and affect many other regions besides the skin, for example the lungs (pulmonary edema) or the brain (cerebral edema).
How do edema develop?
Normally, a balance between the fluid transfer from the smallest blood vessels - the arterial capillaries - in the connective and supporting tissue and the outflow of tissue water into the venous capillaries and its discharge via the lymphatic vessels. In edema, this fluid exchange between the capillaries and the tissue is disturbed, that is, more water is transferred to the tissue than is transported away.
This is the case, for example, with all diseases that affect the circulation, such as cardiac and renal insufficiency. In the former, the pumping power of the heart is impaired, so that the return to the heart is restricted and the water - according to gravity - collects especially in the area of both ankles and dorsum. In the case of renal insufficiency, proteins are eliminated with the urine, which otherwise attract the water in the blood and thus hold it back.
Other common causes of edema include cirrhosis of the liver (leading to edema = ascites), allergies and medications such as calcium channel blockers used in heart disease. Also, some congenital diseases are associated with edema.
Common forms of edema
- Leg edema: Water build-up in the legs occurs, for example, from weak veins whose venous valves are no longer functioning well enough. The spent blood, which should actually be transported to the heart, sags in the legs. As a result, a high pressure builds up in the vessels, too much liquid is forced out of the blood into the surrounding tissue; the leg swells. Other causes include cardiac and renal insufficiency.
- Pulmonary edema: The most common cause of fluid leakage from the capillaries into the lungs is chronic weakness of the left ventricle - the blood is not sufficiently pumped into the large circulation and accumulates back into the pulmonary circulation. Other causes include kidney weakness, lung disease and altitude sickness.
- Cerebral edema: The life-threatening increased fluid retention or rearrangement in the brain tissue is caused by various external and internal disorders, such as tumors, inflammation, poisoning, vascular damage, brain diseases, injuries, surgery or altitude sickness. Since the bony skull has no way to expand, the edema can compress important brain areas and supplying vessels, resulting in reduced blood flow and tissue dying.
- Angioedema: Formerly known as Quincke edema, this accumulation of water in the subcutaneous tissue is a fugitive, often massive swelling, especially on the face (lips and eyelids), less commonly on the tongue, genitals and other organs. They usually do not itch, but they can be painful, depending on the severity of the swelling. If the larynx is affected, there is even danger of suffocation. Normally, angioedema returns within one to three days. It occurs either as part of an allergic reaction (mediated by the messenger histamine) or - much less often - due to the insufficient function of a particular molecule (C1 inhibitor), which slows down the immune system in uncontrolled reactions. This form is usually innate (hereditary angioedema).
A special form is lymphedema, in which the lymph nodes are not functional or have been destroyed or removed due to a disease (eg cancer). As a result, tissue fluid and degradation products can no longer be sufficiently removed. It comes to swelling of the tissue, which may affect only individual limbs, but also the whole body. The tissue is bloated and doughy, the swellings are - in contrast to the "normal" edema - difficult to depress.
Therapy of edema
Since edema is an expression of an underlying disease, its treatment comes first. Often, the severity of edema (or its decline) is a good indicator of whether the therapy is suggestive of, for example, cardiac or renal insufficiency. Depending on the location and extent of the edema, intensive care treatment is necessary - for example, brain edema and pulmonary edema.
Swelling in lymphedema is treated with special compression stockings or gloves and sleeves that exert pressure on the limbs; the affected limbs are stored high. Special massages (lymphatic drainage) and physiotherapy provide additional relief.