Whether a baby with hydronephrosis should drink more or less water depends on the severity of the hydronephrosis. If the hydronephrosis is severe, it is recommended to drink as little water as possible and to visit the pediatric surgery clinic as soon as possible to have the obstruction removed surgically to relieve the hydronephrosis. If the hydronephrosis is mild, you can drink water appropriately, but it is important to dynamically observe the changes of hydronephrosis. If the condition worsens and more serious obstruction occurs, you need to go to the pediatric surgery clinic promptly and under the guidance of the doctor for proper treatment to relieve the hydronephrosis as soon as possible.