The common clinical causes of unilateral foot swelling in the elderly are as follows: First, the formation of unilateral lower limb thrombosis, the formation of thrombus in the femoral vein of the patient, the blood return to the lower limb is obviously obstructed causing the blood in the lower limb to pool in the varicose blood vessels, causing the symptoms of swelling, which can then be diagnosed or ruled out by performing ultrasound of the veins of the lower limb. If there is indeed a thrombus in the vein, the patient can be injected subcutaneously with low molecular heparin, orally with rivaroxaban, and wear elastic stockings on the lower limbs to promote blood return and dissolve the thrombus, so as to reduce the symptoms of swelling in the feet, but attention must be paid to the prevention of pulmonary embolism. Second, unilateral saphenous varicose vein, the blood in the superficial blood vessels of the patient’s lower limbs cannot participate in the blood circulation of the whole body, and a large amount of blood stagnates in the superficial blood vessels causing the swelling of the feet, the patient can surgically strip the varicose blood vessels to relieve the symptoms of swelling of the feet.