My Granddaughter Is 9 And Having A Renal Sonogram After

My granddaughter is 9 and having a renal sonogram after having a significant amount of blood in the urine... No pain or other symptoms... What do you think they would be looking for? I read the lab report and there is also significant bacteria . It was sent for culture. In my mind obviously a UTI. But why the ultrasound? I am an RN