Idiopathic edema usually occurs in premenopausal women, typically from 20 to 40 years of age.

Pathogenesis: unclear. There appears to be increased orthostatic fluid retention associated with venous pooling and/or shifting of intravascular volume into the interstitial space.


Possible associations:

(1) diuretic use or abuse

(2) hormonal factors such as oral contraceptives



(1) exclusion of systemic disease

(2) discomfort in areas of fluid accumulation

(3) headaches

(4) weight gain throughout the day


change in weight during the day in kg =

= ((weight in the evening) - (weight in morning with an empty bladder and before fluid intake)


A change > 0.7 kg supports the diagnosis of idiopathic edema.


A more complex exam is the water loading test which entails drinking non-iced water at 20 ml/kg body weight (up to 1,500 mL) and then measuring urine output over several hours. The test is conducted over 2 days, with the patient staying erect on day 1 and being recumbent on day 2. In idiopathic edema the urine output is < 55% of water intake while erect and > 65% when recumbent.

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