Since you already know the size of the stone presently in your right kidney, I must then assume that you are currently under the care of a physician who performed a Cat Scan to obtain that information. Yes, a stone of that size is very serious and yes, it will take surgery again to remove it most likely. Be thankful that you have a physician on top of this for you at this point. As to how you can prevent any more stones from forming, after 30 plus years of suffering with these darn things and after 35 plus stones to date, all I can tell you is what a Urologist told me years ago. "You can do everything you can to try and reduce the number of stones your body produces, and it will reduce the total number but in the end, if your body produces stones, you will eventually get/have more". What you are doing, the medication, the dietary limitations, drinking as much water daily as you can, etc, should all help, but in the end the truth is that you will probably have another stone(s) sometime. I'd also stop drinking those sodas and replace them with drinking more just plain water. I am of a rather thin build so I do not know how your being obese figures into this equation, but shedding some of your excess weight couldn't help but to improve your overall health situation all the way around too. It might even help in this area too, but I'm not sure. Have you had any of your stones analyzed to date to see what they are primarily made of? If not, getting that info and then avoiding what those stones are made up of could help you tremendously. For example, if they are made up of calcium, then your staying away or limiting your intake of products with calcium might help, as you are doing with dairy products. Remember though, not all stones are calcium based. Any future surgeries may be painful but the alternative, with a stone as large as the one you have now, could be deadly. Thank God that they have the procedures to remove it. Good Luck and please let us know how you make out with the present large stone you now have.