In adults, a urine output of less than 400 ml per 24 hours is considered oliguria, and less than 100 ml is considered anuria. Causes of oliguria include pre-renal hypovolemia, renal failure, and post-renal obstruction. A rehydration test can be used to determine whether urinary function is normal and what is causing the abnormality. The rehydration test requires an intravenous drip of 500 ml of 5% dextrose saline, which is completed within 30 minutes, followed by hourly urine collection and measurement of urine output for a total of 2 hours. Under normal circumstances, urine output is approximately 20-30 ml per hour. if the urine output is more than 30 ml per hour, the patient’s oliguria and anuria are considered to be due to hypovolemia. If the urine volume is less than 20ml per hour, it can be considered as renal oliguria, that is, it may be acute renal failure oliguria stage and other conditions. At this time, the treatment should be taken to correct the cause of renal failure, as well as the protection of renal function, and should not be treated with infusion.