Abdominal ultrasound shows left kidney showed mild pelvi-calyceal fullness. what is that? what causes that???

Kidney ultrasound: The ultrasound is not the best method to image the pelvi-calyceal fullness but much easier. cheaper than other methods. Knowing why it was ordered is important to interpretation. But wording suggests pelvi-calyceal system contains a generous amount of urine (can be normal). Go to wikipedia to review the pelvi-calyceal system. You need to discuss the findings with your Dr who ordered the US.