question: I had left-sided pain last week. I thought it was a kidney stone. (I ve had them many times before). have stage 3 kidney disease. The doctor at Urgent Care felt a mass on my left side and had me go to ER. I had a CT Scan and and a stomach ultrasound and vaginal ultrasound. They found a stone in my right kidney. The ER Doctor said she felt a mass on my left side, too. But there were no problems with my tests. The pain subsided for 2 days and now it s back. Any idea what it could be?