Chronic kidney disease is diagnosed when there is kidney damage or decreased kidney function for a period of time greater than or equal to 3 months, regardless of the cause. It includes nephrotic syndrome, chronic nephritis, and renal failure. Chronic kidney disease can be clinically divided into: renal compensated stage, renal decompensated stage, renal failure stage, and uremic stage. The diagnostic criteria for chronic kidney disease are: renal impairment ≥ 3 months (renal impairment refers to abnormal renal structure or function), with or without decreased glomerular filtration rate, as evidenced by one of the following: 1. pathological abnormalities; 2. indicators of renal impairment, including abnormal blood or urine composition, or abnormal imaging; or without glomerular filtration rate < 60 ml/min/1.73 m2 ≥ 3 months, with or without renal impairment.