Edema, or fluid retention, has many causes. Two classes of blood pressure medications can worsen the condition. (David McNew/Getty Images)

If a plate of salty buffalo wings makes your feet swell up like balloons, you might be experiencing edema — fluid trapped in the body’s tissues, most often in the feet, ankles and legs. Fluid retention can be an annoyance, but it can also indicate a more serious condition.

What is edema?

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 during menstruation, pregnancy, standing or sitting for long stints, and consuming salty food and drink.

One common cause is venous insufficiency, in which damage to valves in the legs’ deep veins hinders the return of blood to the heart. This causes fluid to collect and pool in the legs and feet. Superficial varicose veins can also cause legs to swell.

The nonsteroidal anti-inflammatory drugs ibuprofen (Advil and its generic cousins) and naproxen (Aleve and its generics) can cause or worsen edema. So can the diabetes drugs pioglitazone (Actos) and rosiglitazone (Avandia). Two classes of blood pressure medications can also have this effect: calcium-channel blockers such as amlodipine (Norvasc and its generics) and nifedipine (Procardia and its generics), and ACE inhibitors such as enalapril (Vasotec and generics) and lisinopril (Prinivil and generics). Hormones such as estrogen and testosterone can also cause edema, as can antidepressants such as phenelzine (Nardil and its generics), and such tricyclics as amitriptyline and nortriptyline.

Swelling often resolves on its own, usually after a few days, says Norman Kaplan, a professor of internal medicine at the University of Texas Southwestern Medical Center at Dallas. “When you sleep, the body absorbs the excess fluid,” he says, although the swelling can persist in people taking blood pressure medicines.

You should be concerned if swelling continues or worsens, warns Kaplan, who notes that fluid retention accompanied by shortness of breath is especially worrisome. That might indicate a fluid buildup caused by a life-threatening condition such as heart failure or kidney, liver or thyroid disease. In the case of heart failure, the abdomen, legs and lungs swell because the heart is too weak to pump blood. That allows fluid to accumulate.

“It’s very common in people with heart failure for fluid to get into the lungs and cause shortness of breath,” Kaplan says. Kidney disease can result in swelling in the lower legs and around the eyes. With liver disease, obstructed blood flow leads to swelling in the abdomen or lower legs.

Treatments to try

One way to combat fluid retention is to reduce sodium intake, says Katherine Zeratsky, a dietitian at the Mayo Clinic in Rochester, Minn. “The average American gets about 3,400 milligrams of sodium a day,” she notes. That’s more than twice the maximum daily intake of 1,500 milligrams recommended by the American Heart Association.

If you are at risk for edema, you don’t have to restrict fluids, but you should avoid sitting or standing for long periods. In serious cases, a doctor may prescribe a diuretic to reduce swelling. Be cautious with dietary supplements that claim to be “natural” diuretics because their effectiveness often isn’t proved, Zeratsky warns, and they can have side effects and interactions with other medications.

Bottom line

The right treatment for swelling depends on the cause. See a doctor immediately if you have serious, persistent swelling; breathing problems; chest pain; cough; or swelling in one leg, with or without calf pain. Such one-sided swelling could be due to phlebitis, a sometimes dangerous vein inflammation. In pregnancy, excessive swelling can be a sign of preeclampsia, a serious disorder.

Copyright 2012. Consumers Union of United States Inc.