When swelling occurs in both legs, it is usually caused by edema, which is an accumulation of fluid in the body tissues. Swelling of the legs is often accompanied by tenderness and pain in the affected area. Generalized edema commonly occurs as a result of damage to major organs or organ failure that disrupts the normal filtration process and causes the body to retain water.
The kidneys are bean-shaped organs that are an important part of the endocrine system. They are responsible for concentrating urine by filtering waste and excess fluid from the blood. Each kidney contains millions of glomeruli, small structures that are allow for proper filtration. Glomerulonephritis is a condition that occurs when the glomeruli become inflamed and lose their ability to filter. When the kidneys are not working properly, excess fluid remains in the blood and can lead to swelling accompanied by pain, especially in the legs, face, eyes, feet and abdomen. Other symptoms of glomerulonephritis include blood in the urine, foamy urine, cough, diarrhea, fever, joint aches, loss of appetite and shortness of breath.
Cirrhosis is the extensive scarring of the liver that develops gradually due to chronic liver damage. Every time the liver is exposed to a toxin, healthy tissue is destroyed and the liver regenerates itself by replacing the healthy tissue with scar tissue. When the liver is constantly exposed to toxins, such as alcohol, the scar tissue accumulates and begins to outweigh healthy tissue. This results in loss of proper liver function. When the liver is not functioning properly, fluid accumulates in the body, causing swelling and pain, especially in the legs and abdomen. Other symptoms of cirrhosis include weakness, fatigue, loss of appetite, nausea, vomiting, weight loss and the appearance of spider-like blood vessels on the skin surface, according to the National Digestive Diseases Information Clearinghouse.
Heart failure is defined as a lack of ability for the heart to pump enough blood to meet the body's needs. Heart failure usually develops as a result of chronic conditions that damage the heart and the surrounding blood vessels, such as high blood pressure and coronary artery disease. According to MayoClinic.com, heart failure usually affects the left side of the heart, but may affect the right side or both sides as well. When the heart fails, it can cause the retention of fluid, which causes generalized swelling and pain, especially in the legs, ankles and feet. Heart failure also results in shortness of breath, fatigue, weakness, irregular heartbeat, persistent cough, abdominal swelling, lack of appetite, nausea and difficulty concentrating.