Heart Failure: This is often the most common cause of bilateral ankle edema due to the increased venous pressure from the failing heart, leading to fluid accumulation in the lower extremities.

Chronic Venous Insufficiency: This condition leads to poor circulation and increased pressure in the veins of the lower legs, causing fluid to leak into the tissues and resulting in edema.
Nephrotic Syndrome: Characterized by significant proteinuria, hypoalbuminemia, and edema, nephrotic syndrome can cause bilateral ankle edema due to the loss of albumin, which helps keep fluid in the blood vessels.
Liver Cirrhosis: Cirrhosis can lead to hypoalbuminemia and increased venous pressure, causing fluid to accumulate in the lower extremities.
Hypothyroidism: Although less common, hypothyroidism can cause edema 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 this diagnosis as it can lead to pulmonary embolism, a potentially life-threatening condition.
Lymphoma or Other Malignancies: Certain cancers can cause bilateral edema, either through direct invasion of lymph nodes or through the production of substances that lead to fluid retention.
Pulmonary Hypertension: This condition can lead to right heart failure, presenting with bilateral ankle edema among other symptoms.

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 among a myriad of other symptoms due to the accumulation of a particular type of fat in the body's cells.
Sarcoidosis: Although more commonly associated with pulmonary symptoms, sarcoidosis can rarely cause edema, including bilateral ankle edema, due to its systemic nature and potential to affect any organ.