Thank you for your query on Healthcare Magic.
The child should be investigated for renal function tests and to assess any obstruction in urine flow.
He should be monitored regularly to assess there is any increase in the size of cysts periodically.
And his family members also screened with ultrasound
to look for any cysts in the kidney
as some are familial cysts.
I advise you to consult the pediatrician
for further advise.
Hope I have answered your query.