I've always thought of them as ridges too, although they are not very pronounced. My nails have been like this for as long as I can remember... so the kidney thing is kind of scary. Any links you could share with us on that? the anemia sounds more likely in my case though as I do recall being told by the family doc to try supplementing with iron in my early teens after a blood test.
My nails have always grown very quickly though despite the vertical lines, having to clip them down weekly.(maybe that has nothing to do with it though)