Thanks for the query.Hydronephrosis
means swelling over the kidneys. It occurs when there is an obstruction to the passage of urine any where in the urinary tract
Depending on the severity and cause of the obstruction, the patient may have a range of symptoms from asymptomatic to urine infections to kidney damage.
So I suggest a visit to a pediatric nephrologist/urologist
as soon as possible.
Hope this helps