Also known as leg swelling, a number of factors can cause leg edema, a common condition that can range from mild to severe. Most causes of edema begin through either actions or medications that place extra pressure on your capillaries (tiny blood vessels in your body). The more pressure on the capillaries, the more swelling that results.
Activity and Medication
In mild instances, contributing factors such as pregnancy, standing or sitting for a long period of time, or even eating excess amounts of sodium can place extra pressure on your capillaries.
Doctors prescribe certain medications specifically to constrict or enlarge your blood vessels or have this effect on your body. These include vasodilators, which open your blood vessels; calcium channel blockers; nonsteroidal anti-inflammatory drugs; diabetes medications (specifically types known as thiazolidinediones); and estrogens. Each of these medications have been linked with their effects on the body's capillaries.
Effects on Your Body
Whether through medications or actions, the increased pressure on your capillaries causes them to leak. The kidneys react to this leakage by retaining sodium and fluid in your blood vessels to compensate for the increased fluid loss. The increased fluid puts further pressure on your capillaries, which causes even more swelling in your body. When your capillaries begin to retain too much fluid, this is leaked into the surrounding tissues, resulting in swelling.
Causes Related to Medical Conditions
A number of more serious conditions have been linked with leg edema. One example is congestive heart failure, which is a condition that affects your heart's lower chambers and decreases your heart's ability to pump blood effectively. If the blood backs up in your legs or feet, this results in swelling.
Cirrhosis, which affects your liver, also causes edema. Your liver is responsible for regulating fluid in your body. The reduced ability to properly regulate fluid causes swelling, as well as increased pressure in your portal vein, which is a large blood vessel in your body that carries blood to organs in your abdomen.
Diseases that affect your kidneys also can cause leg edema, because your kidneys are not as effective in eliminating salts and fluids in your body. The excess fluid creates pressure on your blood vessels, causing edema.
An additional leg edema cause is a more severe form of edema known as lymphedema. This condition occurs when your body's lymphatic system is damaged, most often due to cancer treatments or infections. The lymphatic system is responsible for draining fluid away from tissues; therefore, when your lymphatic system is damaged, leg swelling occurs.