Chronic Venous Insufficiency: This condition is the most common cause of bilateral leg edema, resulting from the veins' inability to send blood back to the heart due to valve issues, leading to fluid accumulation in the legs.

Heart Failure: Bilateral leg edema can be a symptom of heart failure, where the heart is unable to pump enough blood, causing fluid buildup in the body, particularly in the legs.
Nephrotic Syndrome: A condition characterized by excessive loss of protein in the urine, leading to low albumin levels, which can cause fluid to leak out of blood vessels and accumulate in the legs.
Liver Cirrhosis: Cirrhosis can lead to fluid retention and edema due to hypoalbuminemia and portal hypertension.
Hypothyroidism: Although less common, hypothyroidism can cause edema due to the accumulation of mucopolysaccharides in the skin and other tissues.

Deep Vein Thrombosis (DVT): A blood clot in the deep veins of the legs, which can be life-threatening if it breaks loose and travels to the lungs (pulmonary embolism).
Lymphoma or Other Malignancies: Certain cancers can cause edema by obstructing lymphatic or venous return.
Sepsis: Severe infection can lead to fluid leakage from blood vessels, causing edema.

Lipedema: A rare condition characterized by the abnormal growth of fat cells in the legs, leading to swelling and edema.
Fabry Disease: A genetic disorder that can cause edema due to the accumulation of a particular type of fat in the body's cells.
Milroy Disease: A rare, inherited condition that affects the lymphatic system, leading to chronic swelling of the legs.
Sarcoidosis: An autoimmune disease that can cause edema by affecting various organs, including the lymph nodes and lungs.