Hello and welcome to HealingWell. I am sorry to hear of the swelling in your Father's ankles and feet - this is known as peripheral edema. To determine the cause of his swollen feet, his doctor will ask him to describe his symptoms and provide a detailed medical history. He will be able to tell a lot about your Father's swollen feet just by looking at them. Whether the swelling is in one foot or in both feet and whether it is accompanied by other symptoms (pain, redness, warmth, skin discoloration) can help identify the cause.
Meanwhile, (until you can get your Father to go to the Drs.) there are things you may try at home to decrease the swelling like elevating his feet when he is resting, wearing good shoes, watching his salt intake in his diet, and walking to improve circulation.
It is important for him to pay attention to his feet and for you to keep on talking with him re seeing his Drs. You are doing your Father a great service in trying to get him medical attention.
Remember, I am not a Dr. and HealingWell should never take the place of a medical professional.