Does anyone know anything about CT scans?

I got a CT scan done to see if I had kidney stones, and it was negative. The more I think about it now, I had my gallbladder removed 3 years ago and was reading into gall stones in the bile ducts. If this is what is it, would the CT scan have picked up on it? Or is that a different test? I've been really nauseous, and have had pain in my back and under my ribs where my liver is. Could this be stones again?