What Causes Tenderness In Left Side Of The Waist?

I'm awaiting the results of a scan, intended to help diagnose extreme pain in the left kidney region. (I feel rotten and am dosed heavily with painkillers.)
Recently i have been puzzled by a tenderness at my waist, at the left side, though there is nothing to show for this--no swelling, spots, redness etc.
Are the two symptoms connected?
Thanks
Chris