Edema is sometimes caused by damage to or pressure within veins
that causes them to leak fluid — blood plasma that is mostly
water — into nearby tissue. (At other times, edema is caused by
heart, kidney or liver disease that causes water to accumulate
in the lungs, abdomen and elsewhere.) Fluid usually pools in the
feet, ankles and legs, but it can also be more generalized
throughout the body. Swelling can either disappear overnight or
persist. The severity and duration will depend on the condition
causing it. Fluid retention has many causes, and not all of them
are alarming, says Ann O’Hare, an associate professor of
medicine at the University of Washington in Seattle. “Many
people will get some mild ankle swelling when they are on a long
plane ride, or they may get hand swelling on a hot day,” O’Hare
says. “It’s nothing to worry about if it resolves within a day
or two.” Peripheral edema, the term for swelling or fluid
buildup in the lower legs or hands, can be brought on by such
things as hormonal changes