Low density lesion found on kidney. 5mm in size. what does this mean?

It is probably a cyst and should be described a little better in the report along with the possibilities

I agree with Dr. Tandan the lesion could be consistent with a simple cyst. However, it is more helpful if we know the reason for kidney ultrasound. Give example: if you have this US done because of blood in the urine, the interpretation of that low density lesion may be changed or further test needs to be done for clarification because simple cyst of 0.5 cm is rarely the cause of hematuria.