I started getting kidney stones a few months after my T2 diagnosis prompted me to go on low-carb diet. At the time I had greatly stepped up my exercise, without hydrating enough. After the first stone episode, I greatly increased my water/fluid intake to a minimum of 4 liters per day (this takes quite a lot of dedication to achieve). I also reduced oxalate-containing foods, stopped taking a calcium supplement, and added a large glass of freshly squeezed lemonade to my lunch. Despite all of this, I had another stone episode about five months later. After that, the specialist ordered a "24-hour urine test" which showed that the calcium level in my urine is incredibly high (it came in at 430, while a normal reading is 250 or below). This, the doctor says, likely explains why I continued to get kidney stones. He put me on a low-sodium diet, which he said will help, but is unlikely on its own to bring down the urine-calcium level enough. We are doing another 24-hour urine test next month to get a new calcium reading.
That doctor, as well as another kidney specialist I have consulted, are both pessimistic that the low-sodium diet will be sufficient. They want to add a diuretic drug call a thiazide, which although primarily used to treat high blood pressure, is also effective in lowering urine calcium levels. I am battling this tooth and nail, but remain open-minded for the time being. I do not have any signs of underlying kidney disease, so the kidney stones are just a big (and very painful) nuisance. If they turn out to be only occasional, I would rather put up with them than take a fairly strong drug for the rest of my life. I also want to continue in drug-free mode for a while to make absolutely sure that the kidney stone issue is chronic, rather than just something that happened a few times and could never happen again.
Hope this helps! For what it's worth, neither of my two kidney specialists is terribly interested in the low-carb issue. Also, because I never had a 24-hour urine test before now, I have no idea whether my high urine calcium is a lifetime issue, or whether it only started recently.