'Radioplaque density' - kidney stone?

I know I have a kidney stone in my left kidney, which is being monitored at the local hospital. After my last x-ray, a few weeks ago, the stone hadn't changed size, but, according to my copy letter from the consultant, I now have 'some areas of radiopaque density' in my right kidney.

I don't have to go back for another two years, so, obviously, the consultant isn't concerned. I've made the assumption that this 'density' indicates another stone in my right kidney. Can anyone tell me if this what it means?