Orthostatic Edema: Definition and Pathogenesis
Orthostatic edema is defined as a disorder characterized by edema that becomes detectable after a period of time (no more than 12 hr) in the sitting or standing posture and that disappears spontaneously in recumbency. Its occurrence does not depend on intrinsic cardiac, renal, hepatic, or obstructive venous disorders, nor is it associated with an abnormal tendency to retain fluids in recumbency. A specific maximal duration of orthostasis required for the development of manifest edema has to be included in the definition, as ankle edema may develop in individuals in robust health after more prolonged periods of sitting or standing. Thus, pitting edema was readily demonstrable at the ankles of six healthy passengers (three of them males) that I was able to examine at the end of a flight from various American cities to Copenhagen, via Amsterdam, which lasted 15–16 hr, in 1960. In unusually hot weather, too, it is common for persons in apparently good health to note some puffiness at the ankles after being on their feet all day. For this reason, orthostatic edema should be considered present when edema is evident after what might be considered a “normal” day’s activity, under “normal” environmental conditions.
KeywordsPlasma Volume Upright Posture Sodium Excretion Urine Flow Rate Water Load
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