ATN is the medical abbreviation for acute tubular necrosis, which is the most common cause of acute renal failure. Common causes of its occurrence include renal ischemia, or sudden hypotension, shock haemorrhage resulting in inadequate renal perfusion, renal ischemia, hypoxic necrosis induced by acute tubular necrosis. In addition, poisoning is also a common cause of acute tubular necrosis, including drug poisoning, heavy metal and chemical poisoning, etc. When acute tubular necrosis occurs, the typical clinical manifestations can be divided into three stages, which are oliguria, polyuria and recovery stage. In the oliguric phase, patients with urine volume <400ml/d will have disorders of water-electrolyte and acid-base balance, and acute renal failure will also occur, such as a significant increase in blood creatinine and urea nitrogen. After the polyuric phase, the urine volume gradually increases to >2500ml per day, and at this time, because the patient is in the polyuric phase, disorders of water-electrolyte and acid-base balance will still occur.