So I've read some articles, and even a study that makes the assertion that diet soda has a direct negative effect on kidney health... I asked my nephrologist and she's all like "No, diet soda is A-OK".
Has any of your doctors said otherwise?
Maybe you're thinking of the hype following one of the statistical correlations observed in the Nurses' Health Study. Dr. Lin, who happens to have been my independent evaluating nephrologist, found that most consumers of more than two diet sodas a day, on average, also displayed a more rapid annual decline in glomerular filtration rate than those who didn't. http://www.webmd.com/diet/news/20091102/diet-sodas-hard-on-the-kidneys
Lots of hysterical warnings have been lumped into the sugar vs. sweeteners media wars. This one got added to the mix four years ago. As far as I know, this is as serious as the indictment gets, and neither the mechanism or the long term hazard profile is better explained yet. Make your own decision. I use sucralose in my morning tea, but I don't drink soda, not even diet. Best wishes.
I have read studies that indicate that consumption of dark-colored sodas such as colas (regardless of whether they are diet or regular) increases the risk of developing kidney stones. That's not exactly a kidney "disease" but when you have only one kidney a stone can be especially troublesome or dangerous. Seems to have to do with the coloring agent(s) rather than the type of sweetener when it comes to kidney stones.
Fr. Pat