Chronic Venous Insufficiency: This condition is a common cause of bilateral lower extremity edema, especially in older adults or those with a history of deep vein thrombosis. It occurs due to the incompetence of venous valves, leading to blood pooling in the legs.

Heart Failure: Bilateral edema can be a sign of right-sided heart failure, where the heart is unable to pump blood effectively, leading to fluid buildup in the body, particularly in the lower extremities.
Nephrotic Syndrome: A condition characterized by excessive loss of protein in the urine, leading to hypoalbuminemia, which causes fluid to shift from blood vessels into interstitial spaces, resulting in edema.
Liver Cirrhosis: Can cause edema due to hypoalbuminemia and portal hypertension, leading to fluid accumulation in the lower extremities.
Hypothyroidism: Sometimes associated with edema, possibly due to the accumulation of mucopolysaccharides in the skin and other tissues.

Deep Vein Thrombosis (DVT): Although DVT typically presents unilaterally, it's crucial not to miss it, as it can be bilateral and poses a significant risk of pulmonary embolism.
Lymphoma or Other Malignancies: Certain cancers can cause edema by obstructing lymphatic or venous return.
Superior Vena Cava Syndrome: Obstruction of the superior vena cava can lead to edema of the upper body but can also affect the lower extremities if the obstruction is significant and affects venous return indirectly.

Lipedema: A chronic condition characterized by the abnormal growth of fat cells in the legs, leading to swelling and edema.
Fabry Disease: A genetic disorder that can lead to edema among other systemic symptoms 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 (lymphedema) of the legs.