Causes of Water in the Lungs

Your body is composed of more than 60 percent water, and your lungs are made up of close to 90 percent water, according to the U.S. Geological Survey. Water in the lungs, a condition called pulmonary edema, refers to too much water where it does not belong, in the delicate, microscopic air spaces where oxygen and carbon dioxide exchange with your bloodstream. Pulmonary edema has been likened to drowning in your own body water. It is a potentially life-threatening condition and needs quick treatment.

Two doctors look over the x-ray of a pair of lungs.
Credit: KatarzynaBialasiewicz/iStock/Getty Images

Left Heart Failure

You have two hearts--a right and a left heart--living side-by-side in one organ, pumping blood that is almost entirely composed of water. Your right heart, the right atrium and ventricle, receives blood from your body. Its oxygen has been used up and it is full of carbon dioxide. Your right heart pumps it into your lungs to renew its balance of gasses. Your left heart, the left atrium and ventricle, receive the enriched blood from your lungs and pump it back to your body.

If your left heart is weak--most heart attacks happen there--blood backs up into your lungs. The pressure forces water from your blood into the air spaces. This pulmonary edema can drown you internally.

Water Overload

Like too much air in a tire, too much water in your blood builds up pressure in your blood vessels. At a certain point, especially if your left heart is weak, the extra water squeezes out of your blood and into your lung's air spaces, called the alveoli. The extra water blocks air from the delicate membranes, preventing oxygen and carbon dioxide exchange, and stiffens your lungs so that breathing becomes difficult.

Kidney Failure

Your kidneys--more than a waste elimination system--are your body's pressure relief valve. Your kidneys strain 20 to 30 gallons of water a day out of your blood and reabsorb all but a quart or two--urine containing concentrated waste. Water coming in should be equal to water going out at the end of the day. But in kidney failure, the extra water has no place to go. Your blood pressure builds up and can become water in the lungs--pulmonary edema.

Salt Overload

Salt--sodium chloride--is often simply called sodium when discussing your body chemistry. The sodium concentration in you blood is carefully regulated by a delicate balancing act between your heart, kidneys, blood pressure and a number of glands. Too much sodium intake--a dietary problem--forces your body to retain water to dilute your too-salty blood. This builds up blood pressure and can build up lung water, leading to pulmonary edema.

If you don't limit your sodium intake, your doctor may prescribe drugs called diuretics that help your kidneys relieve extra salt, water and pressure.

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