Lower limb edema is a common clinical disease, and there are many diseases that cause lower limb edema. When encountering edematous diseases, it is necessary to identify them and carry out different treatment modalities for different causes. There are two general causes of edema: 1. Systemic diseases and lower limb edema, which are only partly caused by the manifestation of systemic diseases and local lesions, mainly manifesting as lower limb edema. Common systemic diseases include cardiogenic edema caused by heart failure; nephrotic edema caused by kidney diseases such as nephrotic syndrome; hepatogenic edema caused by liver lesions such as hepatitis, as well as malnutrition edema, inflammatory edema, premenstrual tension syndrome, drug-related edema and idiopathic edema; 2. edema caused by local lesions, most commonly lymphatic edema caused by lymphatic vessel obstruction. There is also a part of edema caused by lower limb veins, such as venous edema caused by inferior vena cava obstruction or lower limb iliac vein disease. There is also edema of the lower extremities due to valvular reflux insufficiency. Inflammatory oedema, allergic oedema and angioneurotic oedema. It is also seen in pregnancy toxicity, scleroderma or dermatomyositis.