What Does The Following Renal Ultrasound Mean?

my 4 yo has has a bad kidney infection and dr orderd a renal us yesterday and report says right kidney messures 7.6cm and left is 7.5cm normal for age is 7.9 +/- 1.0 cm for two standerd diviations result impression is mild pelviectasis seen in the upper poles of the kidneys bilateraly. what is this ple help me find out dont have a appy for a 2 weeks