Having lived through and currently living with CKD, it sounds to me like you might have excess uric acid.. The chemical analysis of numerous stones surgically removed indicated the presence of uric acid. In my case the excess acid caused gout for which I take 150mg of allopurinol every day. Gout is a form of arthritis on steroids and when it acts up, as it frequently does, I experience extreme pain on the top part of my feet. I have tried numerous topical OTC products with little success. Eventually the pain will subside. You may want to ask your nephrologist if you should seek help from a renal dietitician to help you select the best foods for you.