As your child was having dilated pelvicalyceal system on antinatal scans, after birth also abdomen and pelvis scan is required to assess the dilated calicyes and their progression at present.
The site of the obstruction causing the dilatation can be assessed.
In most of children PUJ obstruction is more common and it can be treated by stenting the narrowed part. The function of the kidney
can be known by performing the nuclear scan.
Because these children with dilated pelvicaliceal system are prone for recurrent urinary tract
infections and decreased kidney function if not corrected.
Consult your child urologist
and after evaluation of his urinary tract system, proper intervention can be done if required and nothing to worry.