Lower extremity edema is not only confusing for patients, but also for many physicians. There are so many causes of lower extremity edema, and across so many specialties, that there are many clinical misdiagnoses and treatment misconceptions. However, there are some rules to follow. For example, first clarify a few questions: 1, unilateral or bilateral? 2, is it depressed or non-depressed after pressing? 3, can it be significantly relieved after sleeping? Many lower extremity edema and vascular disease related, and most present unilateral lower extremity, after pressing the depression is not obvious, after sleeping can be significantly relieved. Angioedema is roughly divided into the following cases: 1, lower extremity venous valvular insufficiency, patients are often accompanied by obvious varicose veins in the legs, edema after standing for a long time. 2, lower extremity deep vein thrombosis, mostly seen in unilateral lower limbs, muscle swelling is dominant, dorsal foot edema is not obvious. At the same time, it is accompanied by deep pressure pain in groin or squeezing pain in calf muscles. 3.Deep vein thrombosis in the lower limbs, with a history of venous thrombosis for many years, accompanied by darkening of the calf skin and expansion of superficial veins. 4.Iliac vein compression, left lower limb edema of unknown cause, mostly seen in young and middle-aged women. Lymphoedema Lymphoedema is commonly known as rubber leg, with obvious skin depression after hand pressure. Some patients have a history of “dengue”, with high fever, chills, and red, swollen and painful skin. It tends to involve the lower limbs unilaterally, but the depressions are very obvious on pressure. Other non-vascular edema is characterized by bilateral lower extremities, marked depression, and lack of relief after sleep. Renal edema Symmetrical edema of both lower extremities is associated with renal insufficiency. Eyelid edema is often present in the early morning. Cardiogenic edema Related to cardiac insufficiency. Hypoproteinemia, associated with hepatic insufficiency, with depressed edema not limited to the lower extremities. Pharmacologic edema Mostly seen in glucocorticoids, androgens, estrogens, insulin, and other treatments Hypothyroid edema with hypothyroidism. Idiopathic edema Mostly occurs in women, mainly in the lower parts of the body. The cause is unknown and may be due to endocrine disorders with abnormal response to upright body position. Can elevation of the lower extremities eliminate lower extremity edema? Edema of the lower extremities caused by venous and lymphatic lesions can be relieved by elevating the lower extremities. Lower extremity elevation above chest level is most effective when lying down. Elevation of the lower extremities is not harmless! The amount of circulating blood in the lower limbs accounts for about 1/4 of the whole body, and elevating the lower limbs will increase the burden on the heart. Therefore, patients with high blood pressure and heart disease should be cautious about elevating the lower extremities. The pressure in the arteries decreases significantly after elevating the lower extremities, so patients with severe ischemia in the lower extremities are prohibited from elevating the lower extremities.