I have concretions in my both kidneys..but calculas is not seen in ct scan (kub)..doctor is saying there is no problem with the calculas..but i've pai?

See below : Concretions in the kidney are usually synonymous with small/tiny renal calculi (kidney stones). Usually only visualized on CT scan and too small to be seen on a plain abd. x-ray (KUB). Generally, these are not associated with any discomfort or pain which "usually" only occur if much larger and causing obstruction or passing into the ureter. Would seek out other possible causes of your back pain.