Edema (Swelling of part of the Body)
Edema is defined as an abnormal or excessive accumulation of fluid in the tissue spaces of the body. This component of tissue fluids may expand by several litres before the abnormality is detected. Similarly, the patient will gain weight.
Edema occurs due to a general or local transfer of fluid from blood plasma of capillaries into the tissues.
Treatment of edema focuses on correcting the cause of the fluid accumulation. A low-salt diet usually helps. You also should avoid drinking too much fluid. If you are not short of breath, elevate your legs above the level of your heart to keep swelling down. Your doctor might suggest that you take a low dose of a diuretic (water pill).
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).
Mechanism of Edema Formation
About one third of the total body water is confined outside the cells (extra cellular space). This is composed of plasma and tissue fluid. Plasma itself represents 25% of this extra cellular space. The hydrostatic pressures of the blood and the oncotic pressures of the extra cellular space are so adjusted so as to enable large movements of fluids across membranes between the blood and the tissue spaces.
Pregnancy can cause edema in the legs as the uterus puts pressure on the vena cava, a major blood vessel that returns blood to the heart from the legs. Fluid retention during pregnancy also can be caused by a more serious condition called preeclampsia.
Similarly, oncotic pressures contributed by plasma proteins and the hydrostatic pressures within tissue fluid promote the movement of fluid from tissues to the blood. This is finely balanced and enables large exchanges to take place. Any mismatch will lead to edema.
Types of Edema
1. Generalised Edema (Anasarca, Dropsy): This refers to gross, generalised edema of the body. It may be due to the very low content of proteins in the body as a result of a massive loss of proteins passed through urine. This occurs in cases of severe nutritional deficiency, protein losing digestive disorder, severe chronic liver disease and damage to the kidneys.
2. Localised Edema: This may be due to -
a. Infection e.g. cellulitis, abscess, insect bite.
b. Traumatic e.g. Fractures and sprains.
c. Venous obstruction e.g. Thrombus.
d. Filariasis
e. Physiological e.g. Pregnancy.
Early symptoms of pulmonary edema include:
Symptoms vary according to the type of edema and its location. In general, the skin above the swollen area will be stretched and shiny.
- shortness of breath upon exertion
- sudden respiratory distress after sleep
- difficulty breathing, except when sitting upright
- coughing
In cases of severe pulmonary edema, these symptoms will worsen to:
- labored and rapid breathing
- frothy, bloody fluid containing pus coughed from the lungs (sputum)
- a fast pulse and possibly serious disturbances in the heart's rhythm (atrial fibrillation, for example)
- cold, clammy, sweaty, and bluish skin
- a drop in blood pressure resulting in a thready pulse
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