The kidney function is impaired (manifested by pathological changes, blood or urine related indicators or abnormal imaging) for more than three months, or the glomerular filtration rate (GFR) is less than or equal to 60ml/min/1.73m2 for more than three months. Since there is no obvious characteristic manifestation in the early stage of the disease, abnormalities appear when the kidney function decreases to less than 50% of the normal level, thus it is called “the silent killer”. With the development of the disease, a series of problems such as hypertension, anemia, heart failure, encephalopathy, bone disease and disorders of water-electrolyte acid-base balance follow, which can be life-threatening.