The results of the water fasting test are diagnostic of urosepsis, which is diagnosed and identified by the measurement of plasma and urine osmolality after water fasting. Water intake is controlled prior to the water fasting test, which begins with complete water fasting for about 8 hours, during which time the patient’s physical condition is closely monitored. At the end of the water fasting period, through the measurement of urinary output, plasma and urine osmolality during the period, to make a comprehensive judgment on the physical condition, further diagnosis of uremic syndrome, belongs to the commonly used clinical examination method. The patient in the whole process of urinary output is reduced or only a small amount of reduction, urine osmolality did not rise significantly, after the injection of pressurization, osmolality rose, the clinical will suggest that the central urinary avalanches, after the injection of pressurization has not risen for renal urinary avalanches. After the diagnosis of the corresponding conditions need to consult a doctor in a timely manner, under the guidance of the clinician for standardized treatment, to avoid delays in the condition.