1. CKD in medicine refers to chronic kidney disease, which is a concept put forward by the American Kidney Disease Foundation. Chronic kidney disease refers to kidney damage or glomerular filtration rate below 6ml/min per body surface area for at least 3 months. Renal damage includes abnormalities in renal pathological examination and laboratory indicators of renal damage, such as abnormalities in blood, urine and imaging.

2. According to different clinical manifestations, chronic kidney disease can be divided into five stages: the first stage is a relatively mild glomerular damage period, when the glomerular filtration rate is greater than or equal to 9 ml/min; The secondary lesion is relatively aggravated, and the glomerular filtration rate is 6-89 ml/min. The third stage glomerular filtration rate decreased moderately, mostly at 3-59 ml/min; In the fourth stage, the glomerular filtration rate decreased to 15-29 ml/min; End-stage renal disease is the fifth stage of chronic kidney disease, and the glomerular filtration rate is less than 15ml/min, which is also called uremia stage.