Edema is a pathological phenomenon of excessive fluid accumulation in the interstitial spaces of tissues, and is most common clinically, especially in the lower extremities. Diabetic patients with lower extremity edema, in addition to a few causes, mostly related to various chronic complications of diabetes mellitus, is a sign of many chronic complications. Common in the following cases: 1, diabetes complications renal insufficiency diabetic nephropathy is the most common cause of lower extremity edema in diabetic patients. When renal damage occurs in diabetic patients, it causes bilateral lower limbs, eyelids and facial swelling due to large leakage of urinary protein, decreased glomerular filtration rate and severe hypoproteinemia, and generalized swelling can occur in severe cases. Patients can be distinguished by protein and tubular type in routine urine examination, and elevated renal function indicators (such as creatinine and urea nitrogen). Diabetes mellitus is easily complicated by cardiovascular diseases such as coronary heart disease and cardiomyopathy. In severe cases, cardiac insufficiency (especially right heart insufficiency) may cause stasis and sodium retention in the circulation, resulting in jugular venous anger, hepatosplenomegaly and symmetrical edema of both lower limbs. Such patients are often accompanied by cardiovascular symptoms such as panic, chest tightness, shortness of breath and ischemic changes in the electrocardiogram, which can be distinguished. Diabetic peripheral neuropathy Diabetic neuroedema is mostly seen in both lower extremities and is related to body position and activity. This is due to damage to the vegetative nerves (mainly sympathetic nerves), which causes peripheral vasodilatation and congestion, and edema due to venous stasis in both lower limbs; in addition, increased permeability of local capillaries caused by neurotrophic disorders can also lead to swelling in the lower limbs. Most of the edema caused by diabetic neuropathy is accompanied by numbness, pain, glove-like sensory loss and other symptoms, which can be distinguished. 4.Diabetes combined with lower limb vascular lesions When patients with lower limb venous lesions (such as lower limb deep vein thrombosis, venous valve closure insufficiency), resulting in venous reflux obstruction and venous hypertension, lower limb edema can occur, but often unilateral edema. 5.Diabetes combined with foot infection Patients with foot skin damage infection, local inflammatory response can also lead to edema, these patients are often accompanied by local skin temperature, skin redness, pain and other acute inflammatory manifestations. 6, diabetes combined with severe malnutrition Some diabetic patients, due to long-term excessive dieting, calorie and protein intake is seriously inadequate, resulting in hypoproteinemic and malnutrition swelling. 7. Drug factors Certain hypoglycemic drugs and antihypertensive drugs can cause water and sodium retention, resulting in swelling of the lower limbs. The former, such as insulin, thiazolidinediones (such as rosiglitazone, pyrrolidone); the latter, such as calcium antagonists (such as nifedipine, amlodipine, etc.). The common feature is that edema occurs after the drug is used and disappears soon after stopping. 8, diabetes combined with hypothyroidism Some diabetic patients (especially elderly female patients) combined with hypothyroidism, the latter can cause lower extremity or facial mucinous edema, which is characterized by finger pressure on the edema site does not appear depressed changes. In addition, hypothyroid patients often have fatigue, drowsiness, fear of cold, bradycardia, constipation and other accompanying symptoms, laboratory tests show that low thyroid function (FT3, FT4) can be distinguished. 9, idiopathic edema female diabetic patients with swollen lower limbs, we must pay attention to exclude “idiopathic edema”. This edema often occurs in the reproductive age, patients often accompanied by symptoms of neurosis, edema is often related to the menstrual cycle. A positive “standing water test” will help in the diagnosis of idiopathic edema edema. 10.Other diabetic patients with chronic liver disease may also develop lower limb edema. Patients with chronic liver disease manifestations (such as weakness, liver disease face, liver palm, spider nevus, jaundice, etc.) and liver function abnormalities, combined with liver and biliary ultrasound examination can be distinguished. In conclusion, the causes of diabetic edema are multifaceted and should be analyzed specifically in the context of the patient’s specific situation, with a view to identifying the causes and providing targeted treatment.