I know because of blood tests and a biopsy. Unfortunately, I got into a very very stressful period about two years ago and didn't handle it right. That's one of the reasons I'm online now, to keep to a good protocal, keep positive and constructive. :)
Thanks to financial difficulties and working only periodically from home, I didn't drink enough water, had a very badly abcesed tooth constantly causing tons of white blood cells, and my liver got congested due to stress, lack of exercise and learning how to gourmet cook. The combo of all that caused scarring of the filtration system of the kidneys. Nothing to do about that but protect them and hope the damage doesn't worsen. I don't have stones.