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Excess extracelluar fluid (ECF) due to any cause.

You will commonly find local oedema associated with the inflammatory response (eg an insect bite) or obstruction of lymphatic drainage and gravitational oedema associated with conditions such as cor pulmonale, nephrotic syndrome and cirrhosis. The later conditions produced a clinical picture historically termed as dropsy.

Oedema results from a failure of ECF pressure homeostasis affecting either hydrostatic pressure or osmotic pressure or both, but the breakdown can be quite complex in conditions as diverse as cirrhosis and wet beri beri, where cytokine activation and membrane permability can be as important as the low colloid osmotic pressure of albumin or thiamine induced heart failure respectively.

Gravitational oedema results from the resilience of the tissues and mechanisms for removing fluid from the dependent parts being overcome by gravity. A reverse effect occurs early after entry into microgravity in orbit when the face and upper body is engorged by fluid which moves cephalad. This is reduced during a flight, which in turn reduces the capacity of newly-returned astronauts to withstand gravity.

Gravitational oedema may therefore be treated by inversion - or at least a reduction of the vertical head of pressure by raising the feet to the height of the heart or as close as is achievable; by increasing the support of the tissues with immersion to heart level, or by elastic stockings of a suitable tension and gradient. Movement also improves it. None of these is easy to enforce or put into effect.

Treatment of gravitational oedema by diuretic drugs is less logical, is inclined to cause other problems and is not wholly without effect. Try the other measures.

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