Overhydration for those on tx drinking tooo much water

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Overhydration

Contributor: L. III, MD

Overhydration is an excess of water in the body.

Overhydration occurs when the body takes in more water than it loses.

The result is too much water and not enough sodium. Thus,

overhydration generally results in low sodium levels in the blood

(hyponatremia). Usually, drinking large amounts of water does not

cause overhydration if the pituitary gland, kidneys, liver, and heart

are functioning normally. To exceed the body's ability to excrete

water, an adult with normal kidney function would have to drink more

than 2 gallons of water a day on a regular basis.

Overhydration is much more common among people whose kidneys do not

excrete urine normally--for example, among people with a disorder of

the heart, kidneys, or liver. Overhydration may also result from

syndrome of inappropriate secretion of antidiuretic hormone (SIADH).

In this syndrome, the pituitary gland secretes too much antidiuretic

hormone, stimulating the kidneys to conserve water.

Brain cells are particularly susceptible to overhydration (as well as

dehydration). When overhydration occurs slowly, brain cells have time

to adapt, so few symptoms occur. When overhydration occurs quickly,

confusion, seizures, or coma may develop.

Doctors try to distinguish between overhydration and excess blood

volume. With overhydration and normal blood volume, the excess water

usually moves into the cells, and tissue swelling (edema) does not

occur. With overhydration and excess blood volume, an excess amount

of sodium prevents the excess water from moving into the cells;

instead, the excess water accumulates around the cells, resulting in

edema in the chest, abdomen, and lower legs