Hi I Wanted To Find Out If A 17mm T2

Hi I wanted to find out if a 17mm T2 hyperintense cyst of Rt kidney is something serious? I also found out from MRI that I have a 9mm T2 lesion on the left kidney. How large before the cyst/lesions are serious? Thank you. Reason for MRI is that I have been having pain on my right side of back which radiates from the middle of back.