Lower limb edema is a very common symptom and sign in daily life, either slowly or suddenly, either unilaterally or simultaneously in both lower limbs. The causes are diverse and can be divided into two main categories: edema of the limbs caused by medical diseases and edema caused by surgical diseases. Common medical diseases that can cause lower limb edema include cardiogenic, which is seen in right heart failure caused by various heart diseases; nephropathic, which is mostly seen in nephritis and nephrotic syndrome; hepatopathic, which is seen in liver cirrhosis and hepatocellular carcinoma; malnutrition, which is caused by long-term poor diet and anemia; endocrine disorders, such as hypothyroidism and rheumatism, gestational hypertension syndrome, idiopathic edema, etc. Edema caused by internal diseases is mostly systemic, with lower limb edema appearing on both sides at the same time, occurring slowly, and the swelling cannot subside by lying down or elevating the affected limb, and the edema can be relieved only through systematic treatment of the primary internal diseases. Here we would like to focus on lower limb edema caused by surgical disease factors, especially edema caused by lower limb vascular diseases. The most common diseases are chronic lower extremity venous valve insufficiency and lower extremity deep vein thrombosis. Lower extremity venous valve insufficiency is mainly caused by congenital venous valve dysplasia or acquired strain, cold, trauma and other factors that lead to venous valve damage, poor closure, venous blood reflux stagnation in the blood vessels, long-term venous hypertension causes limb edema; mainly manifests as slowly appearing bilateral or unilateral lower extremity swelling, generally starting from the distal calf and ankle, early without special discomfort, mainly With the development of the disease, leg swelling will gradually become obvious, accompanied by discomfort such as soreness, swelling and pain, light in the morning and heavy in the evening, and skin pigmentation with itching, eczema or skin ulcers, or superficial varicose veins will appear in the serious stage of the disease. It should be clear here that simple varicose veins of lower extremities usually do not cause leg swelling, but if varicose veins of lower extremities appear first and then slowly develop edema of lower extremities after several years, it means that at the same time there is a combination of lower extremity deep vein valve insufficiency or traffic branch valve insufficiency, and similar symptoms mentioned above will also appear. Lower extremity deep vein thrombosis is another important disease causing leg swelling, mostly seen in unilateral extremity, but also can develop bilaterally at the same time, with the main manifestation of sudden limb swelling, distension and pain. Risk factors for lower extremity DVT include advanced age, hyperlipidemia, diabetes, malignancy, pregnancy, estrogen consumption, major surgery, especially orthopedic surgery, limb trauma, chronic disease and long-term bed rest, etc. However, about half of the patients have no clear cause, and a few patients are related to congenital hypercoagulable diseases, such as thrombin III deficiency, protein C and protein S deficiency. The sudden swelling of the limb should be seen in time, and through systematic anticoagulation and thrombolysis, most of the thrombus can be eliminated, the blood vessel will be restored, and the swelling will be relieved soon; once delayed or mistreated, chronic old thrombus will be formed, and the thrombus will be gradually mechanized and hardened, and left in the lumen to cause lower limb venous blood return obstruction or valve destruction of blood reflux, which will cause more serious sequelae, similar to chronic venous insufficiency. The symptoms are similar to those of chronic venous insufficiency. Another common limb edema disease is lymphedema, which is a persistent and progressive swelling of unilateral or bilateral limbs, mostly starting from the extremities and gradually developing upward, with depressed edema in the early stage. It is mainly caused by the lymphatic flow obstruction of the limb. The causes are complex, and are generally divided into primary and secondary, due to anatomical or physiological congenital abnormalities of the lymphatic system, which is called primary lymphedema. The causes of lower limb edema are complex and diverse, and only by analyzing the etiology and pathology in detail can we provide targeted treatment.