For the judgment of the severity of hydronephrosis, clinically it is mainly done by kidney ultrasound. If the kidney ultrasound examination reveals hydronephrosis greater than 3cm, this is moderate to severe hydronephrosis, which is a more serious manifestation, and the longer the hydronephrosis, the more serious the hydronephrosis, the more likely the kidney function will be damaged. If the hydronephrosis is not treated in time, it may lead to kidney failure. In addition, some patients with hydronephrosis can be combined with infection, the infection will appear fever, serious pus in the kidneys, so once hydronephrosis occurs, the cause of hydronephrosis should be found as soon as possible, and only timely treatment of the original disease can avoid further aggravation of hydronephrosis.