Dilated Kidney?

At my Dr.'s appt yesterday they did an ultra sound to check my placenta, the Dr. said one of the babies kidneys were dilated and it was more common in little boys than girls and may not mean anything. He said that the amount of fluid the sac had showed her kidneys were working good. I'm still confused though and wondered if anyone could give me a little more information? I go back in 4 weeks to have another ultra sound to check her kidneys, so hopefully everything will be okay. Please share any similar experiences you or someone you know may have had.