I've had this happen to me twice now. Both times, for me, I'm fairly certain I let myself get dehydrated because both times I had been working outside (a lot), not drinking water (or anything) and I was extremely focused on getting my task completed (I'm pretty sure both times it was mulching, planting, outside yard work) but the bad part is, both times, it didn't hit me until around midnight.
The first time, I knew what it was but I thought if I went to the ER they would give me something or do something to make the stone/pain/issue go away but they did not. I go into the ER, I said "I'm 99% certain I have a kidney stone." So what did we do? They jerk around for 4.5 hours, I was never given anything for pain, had an x-ray done (yep it's a kidney stone) and they gave me flomax and said "you'll pass it in a week or two." About 3.5 weeks later I passed it, it was freaking gigantic, how it didn't get stuck is beyond me. I was writhing in pain for about 8 hours.
The second time, same thing, working outside, I got dehydrated, midnight rolls around and I told my wife "I'm going to suck it up and deal with it." That one was much worse, I was in horrible pain for about 14 hours (crying like a baby in pain at times) and the bad part is that the pain came in waves. So I would go level 3-4 to level 10 then back to level 3-4 and back to 10 again the entire time. At about 2:00 p.m., I bounced up, got a shower and I felt fine just like the first one. I passed that one about 3.5 weeks later again, not as big as the first one but still pretty good sized.