Chronic renal failure has a long course and there is already a large amount of kidney tissue destruction, which is replaced by fibrous scar tissue. In this case, the creatinine of the patient cannot fall because the already lost kidney tissue is impossible to regenerate. The aim of treatment is only to slow down the rate of creatinine rise, delay the start of dialysis and prevent and treat various complications. However, the course of chronic renal failure may encounter some factors that lead to a sudden exacerbation of the disease, i.e., the blood creatinine, which was rising slowly at a gentle rate, suddenly increases rapidly recently and an acute exacerbation occurs on a chronic basis. Factors that can lead to an acute exacerbation of chronic renal failure include infection, poor blood pressure control, the use of nephrotoxic drugs or recent combined heart failure. At this point, doctors will carefully look for possible factors and take measures to remove them, and the elevated blood creatinine can fall back after removal. For example, the patient’s blood creatinine has been stable at about 300μmol/L for nearly a year, and it rose to 500μmol/L after the recent infection of pneumonia. After the pneumonia was controlled, the blood creatinine began to fall, and some patients can completely fall back to the original level, but a few patients can only partially fall.