Chronic Venous Insufficiency: This condition is a common cause of bilateral lower leg edema, especially in individuals with a history of prolonged standing, obesity, or previous venous thrombosis. It occurs due to the incompetence of venous valves, leading to blood pooling in the legs.

Heart Failure: Bilateral leg 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 can cause fluid to leak out of blood vessels and accumulate in the legs.
Liver Cirrhosis: Can lead to fluid retention and edema due to hypoalbuminemia and portal hypertension.
Hypothyroidism: Sometimes associated with generalized edema, including bilateral lower leg edema, due to the accumulation of mucopolysaccharides in the skin and other tissues.

Deep Vein Thrombosis (DVT): Although it typically presents unilaterally, bilateral DVT can occur and is a medical emergency due to the risk of pulmonary embolism.
Lymphoma or Other Malignancies: Certain cancers can cause lymphatic obstruction leading to edema. Early detection is crucial for treatment and prognosis.
Superior Vena Cava Syndrome: Obstruction of the superior vena cava can lead to edema in the upper body but can also affect the lower limbs if the obstruction is significant and affects venous return.

Lipedema: A chronic condition characterized by the abnormal growth of fat cells in the legs, leading to swelling and edema, typically sparing the feet.
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), usually in the legs.