First off, I'm not doctor, but I do have extensive personal experience in the kidney
As far as I'm aware, kidney
creatinine levels are, for the most part, mutually exclusive. Again, I'm not a doctor, so it's best to ask your Nephrologist when you see him/her.
As for your 4mm stone, tell your Urologist that you're nervous about its implications, and that you'd like it removed.