Acute tubular necrosis is characterized by azotemia, disturbance of water-electrolyte balance, and other corresponding organ clinical manifestations. The main characteristic changes of acute tubular necrosis are divided into oliguria stage, polyuria stage and the recovery stage of renal function. Oliguria refers to a significant decrease in urine output, accompanied by azotemia, i.e., increase in blood creatinine, which causes the corresponding clinical manifestations, i.e., low potassium, low sodium, high phosphorus, high calcium, and at the same time, other organs are affected, such as the digestive system and the nervous system, etc., which will also cause the corresponding symptoms. Polyuria refers to the gradual recovery of renal function, urine output gradually increases, in addition to the increase in urine output, renal function, i.e., creatinine, urea nitrogen may further increase, and water electrolyte disorders may also occur at this stage. Renal function recovery period mainly refers to the further decrease of creatinine and urea nitrogen, but the whole recovery process needs time, and the complete recovery of renal function takes about one year.