Swollen legs may be caused by physiological factors, or it may be caused by chronic kidney disease, varicose veins of the lower limbs and other pathological factors. 1. Physiological factors: prolonged standing and sitting may cause obstruction of venous return in the lower limbs, resulting in leg swelling. Women who are pregnant may also experience leg swelling due to the pressure on the inferior vena cava caused by the gradual enlargement of the stomach. 2. Chronic Kidney Disease: Chronic Kidney Disease is due to chronic kidney injury caused by various reasons, and patients may have symptoms such as fatigue, increased nocturia, and low back pain. Due to the long duration of the disease, the water metabolism in the body is abnormal, and the body fluid accumulates in the lower limbs, so the swelling of legs will occur. 3. Varicose veins of the lower limbs: Varicose veins of the lower limbs refer to the phenomenon that the superficial veins of the lower limbs are dilated and tortuous, and if deep vein thrombosis is formed, it will affect the venous return, which will lead to leg swelling. Leg swelling may also be caused by other factors, such as side effects of drugs, diabetes, etc. It is recommended to go to the hospital in a timely manner to find out the cause and then treat the symptoms.