The causes of swollen legs and feet in the afternoon are mainly divided into systemic and local causes. The main systemic causes are cardiac insufficiency, renal insufficiency, hypothyroidism and hypoproteinemia. In cardiac insufficiency, the pump function of the heart decreases and the heart’s output decreases, causing blood to pool in the circulation and causing swelling of the legs and feet. In renal insufficiency, fluid drainage is restricted and excessive fluid accumulates in the body, causing edema. In hypothyroidism and hypoproteinemia, edema is caused by a relative increase in tissue fluid. The systemic cause of edema is bilateral lower limb edema, which is characterized by light in the morning and heavy in the evening. Local causes are mainly varicose veins and restricted venous return. Swelling of the lower extremities is obvious after prolonged standing and a day’s exertion, and is manifested only as edema of the affected extremities, which is a manifestation of venous hypertension of the lower extremities caused by venous valve insufficiency and venous regurgitation, and is a manifestation of restricted blood return.