Congenital kidney and urinary tract

Hi- my 18-month-old boy ultrasound is as follows- I think of your opinion if you need to follow up.Anterior posterior diameter of the left kidney pelvis at about 6.It is 3 mm and with mild dilatation of the lower calisons, so grade hydronephrosis is one to two in the left kidney..Was not seen in the upper and lower ureter.