There are many reasons for double lower extremity edema, which may be due to pathologic causes such as nephrogenic, cardiogenic, hepatic, etc.; it may also be due to physiologic factors and other conditions. 1. Pathologic factors (1) Nephrogenic: for example, patients with nephritis will have proteinuria in urine, resulting in a decrease in plasma protein, and plasma colloid osmotic pressure will decrease, resulting in water leaking out of blood vessels into the tissue interstitial space to form edema, so nephritis can cause double lower extremity edema. (2) Cardiac origin: for example, right heart failure will lead to the decrease of right ventricular ejection capacity, the pressure of right ventricle will be increased, and there will be the obstacle of body circulation, which will lead to the water leaking out from blood vessels into the tissue interstitial space to form edema, so heart failure will cause double lower limb edema. (3) Hepatogenic: if the albumin synthesis ability of patients with liver cirrhosis is reduced, it will lead to the decrease of colloid osmotic pressure of blood, which will lead to the exudation of water from blood vessels to the tissue interstitial space to form edema, so liver cirrhosis will cause double lower extremity edema. 2. Physiological factors: due to the patients standing for a long time lead to the patients lower limbs local ischemia will lead to osmotic pressure changes, can also trigger double lower limb edema, this situation does not need special treatment, pay attention to the combination of work and rest, rest elevated lower limbs can be recovered in general. Double lower extremity edema may also be seen in hypothyroidism, malnutrition and other diseases, if the symptoms of double lower extremity edema, you need to consult a doctor in time to check, according to the cause of the corresponding treatment methods.