the accumulation of excess fluid in a fluid compartment. Formerly called dropsy and hydrops . adj., adj edem´atous. This accumulation can occur in the cells (cellular edema), in the intercellular spaces within tissues (interstitial edema), or in potential spaces within the body. Edema may also be classified by location, such as pulmonary edema or brain edema; types found in certain locations have specific names, such as ascites (peritoneal cavity), hydrothorax (pleural cavity), or hydropericardium (pericardial sac). Massive generalized edema is called anasarca . Classification by location does not indicate whether the edema is cellular or interstitial or occupies a potential space (for example, brain edema may be either cellular or interstitial). Edema can be caused by a variety of factors, including conditions that affect osmotic pressure, such as hypotonic fluid overload, which allows the movement of water into the intracellular space, or hypoproteinemia, which decreases the concentration of plasma proteins and permits the passage of fluid out of the blood vessels into the tissue spaces. Other factors include poor lymphatic drainage; conditions that cause increased capillary pressure, such as excessive retention of salt and water and heart failure; and conditions that increase capillary permeability, such as inflammation.

alveolar edema pulmonary edema in the alveoli, usually with hypoxemia and dyspnea.

brain edema cerebral edema .

cardiac edema a manifestation of congestive heart failure , due to increased venous and capillary pressures and often associated with renal sodium retention.

cellular edema edema caused by the entry of water into the cells, causing them to swell. This may occur because of decreased osmolality of the fluid surrounding the cells, as in hypotonic fluid overload, or increased osmolality of the intracellular fluid, as in conditions that decrease the activity of the sodium pump of the cell membrane, allowing the concentration of sodium ions within the cell to increase.

cerebral edema swelling of the brain caused by the accumulation of fluid in the brain substance. It may result from head injury, stroke, infection, hypoxia, brain tumors, obstructive hydrocephalus, and lead encephalopathy; it may also be caused by disturbances in fluid and electrolyte balance that accompany hemodialysis and diabetic ketoacidosis. The most common type is vasogenic edema, which may result from increased capillary pressure or from increased capillary permeability caused by trauma to the capillary walls. Cellular edema may occur in ischemia or hypoxia of the brain. Because the brain is enclosed in the solid vault of the skull, edema compresses the blood vessels, decreasing the blood flow and causing ischemia and hypoxia, which in turn result in further edema. Unless measures are taken to reverse the edema, destruction of brain tissue and death will result.

dependent edema edema of the lowermost parts of the body relative to the heart; it is affected by gravity and position, so that the lower limbs are affected if the individual is standing, but the buttocks are affected if the individual is supine.

generalized edema edema that is caused by poor venous return; it is not localized by the effects of gravity, in contrast to dependent edema.

interstitial edema

edema neonato´rum sclerema neonatorum .

nonpitting edema edema in which pressure does not leave a depression in the tissues, such as in cellular edema . See also pitting edema .

pedal edema swelling of the feet and ankles.

peripheral edema edema affecting the extremities; seen in heart disease, Crohn's disease, and amyloidosis.

pitting edema edema in which external pressure leaves a persistent depression in the tissues (see pitting ); it occurs because the pressure pushes the excess fluid out of the intercellular spaces in the tissue. See also nonpitting edema .

pulmonary edema diffuse extravascular accumulation of fluid in the tissues and air spaces of the lung due to changes in hydrostatic forces in the capillaries or to increased capillary permeability. It is most often symptomatic of left ventricular heart failure , but can also be a complication of mitral stenosis , aortic stenosis , altitude sickness , acute hypertension , volume overload during intravenous therapy, or reduced serum oncotic pressure, as in patients who have nephrosis , cirrhosis , or hypoalbuminemia . During the initial stage of pulmonary edema, patients may complain of restlessness and anxiety and the feeling that they are getting a common cold . Other signs include a persistent cough, slight dyspnea , and intolerance to exercise. On auscultation , rales can be heard over the dependent portion of the lung. As fluid continues to fill the pulmonary interstitial spaces the dyspnea becomes more acute, respirations increase in rate, and there is audible wheezing. The cough becomes productive of frothy sputum tinged with blood, giving it a pinkish hue. Eventually, if the condition persists, the patient becomes less responsive to stimuli as levels of consciousness decrease. Ventricular arrhythmias develop and breath sounds diminish. In some patients these phases are telescoped as the pulmonary edema develops rapidly and the final stages of respiratory insufficiency are evident in a very short period of time. Treatment is aimed at enhancing gas exchange, reducing fluid overload, and strengthening and slowing the heart beat. To accomplish these goals the patient is often given oxygen by mask or through mechanically assisted ventilation. Drug therapy includes diuretics to remove excess alveolar fluid and morphine to relieve anxiety and reduce the effort of breathing. Administration of other medications depends on the cause of the edema, as well as what other problems the patient may be having.

vasogenic edema that characterized by increased permeability of capillary endothelial cells; the most common form of cerebral edema .