I know with a kidney problem there isn't much they can do until after the baby is born and then they can start running tests but make sure they ask for them tests as soon as the baby arrives.
A ultrasound on the baby will show more detail and also they might want to do a x-ray where they insert fluid in to the baby to see if there is a blockage.

I went through all these tests when Alex was born they was meant to start them before we left hospital but because he had other problems they forgot until we where home. Alex still has a slight dilation but nothing to worry about.
They did also think Eleanor was going to have the same problem but it turned out she was okay in the end.