The time for review of hydronephrosis is about 1-3 months, and it needs to be reviewed according to the cause of hydronephrosis. If urinary stones are the cause of hydronephrosis, it is recommended to come to the hospital for a review once in a month after treatment. The purpose of the review is to see if the stones are discharged, and if the stones are discharged, the fluid can be relieved on its own, but if the fluid is caused by congenital ureteral malformation, you need to come to the hospital for a review about 3 months after the surgery. However, in case of unexplained hydronephrosis, in principle, it is recommended to visit the hospital once every 3 months to dynamically observe the changes of hydronephrosis and to clarify the cause of hydronephrosis, and if necessary, to adopt a treatment plan for the cause. Some of the early hydronephrosis may not be obvious, and the volume of the primary disease gradually increases during the observation period, at which time a clear diagnosis can be made for further treatment.