You could use existing medical data to calculate the number of kidney stones patients to be expected for all the ISS astronauts and their stay time. Of course this number is valid for a stay on Earth surface only.
If this number is small, no statistical inference about the frequency of kidney stones in extend microgravity is possible.
From Wikipedia: In ...
Sadly, its just stock content, nothing special.
They do seem to get around, I saw this design, not the video, maybe a short while back.
Note the title is "International space station orbiting earth" - ...