Ladies, when I was pregnant and my baby was diagnosed with dilated kidneys I had contacted another mum on this forum who I recalled went through a similar thing with her child. She recommended Dr Richard Chiu, who specialises in nephrology and was quite senior in the public hospital before moving to private practice. I never saw him myself as my daughter didn't need it in the end, but he might be a good person to see in case you'd like a second opinion.
My daughter had her scans at United Christian Hospital, the radiologist was senior and very good. I think she was declared fine at six months.