I have history of a 1/2" stone 5 years ago in my left kidney. I had lithotripsy which broke it up. I've been fine since, but in March I thought I had another stone - same pain, same kidney. They did a full abdominal ultrasound and told me that I had hydronephrosis, but didn't see a stone. He sent me for an IVP, which came back fine. I waited until yesterday and had another ultrasound done which showed nothing. The pain is dull and achy on my left side in front, and sometimes also back (kidney area), and sometimes with nausea. It is every day, coming and going. Occasionally stabbing or feeling like something is grabbing/tugging something in there. Any ideas on what this could be? He is sending me for a CAT scan next Tuesday because he didn't want to quit options because of the pain. Any help appreciated.