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This answer to What are the main impacts on the body of an astronaut exposed to long term zero gravity? mentions that the increase in bone loss due to extended periods of time in microgravity can not necessarily be 100% mitigated by exercise.

Bone loss means higher calcium and other minerals in the blood since that's where it's lost to.

Higher mineral levels in blood might increase predisposition to kidney stone formation

Question: Does extended microgravity increase the rate of kidney stones in astronauts? If so, do these lead to medical complains and/or discomfort while still in space?

Kidney stones are mentioned in answers here and here but are more definitive results available?

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    $\begingroup$ Discomfort from kidney stones would be putting it mildly. Over time I've heard a number of people, mostly women, describing the pain of kidney stones for men being the closest thing they could experience to the pain of child birth. Having once experienced a suspected kidney stone I don't want to experience it again, suspected or otherwise. $\endgroup$
    – Fred
    Aug 3 '21 at 10:21
  • $\begingroup$ @Fred are they intensely painful from the start, or do they start as discomfort and then get worse over time? $\endgroup$
    – uhoh
    Aug 3 '21 at 10:22
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    $\begingroup$ Some interesting pictures of kidney stones & these. $\endgroup$
    – Fred
    Aug 3 '21 at 11:05
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    $\begingroup$ @uhoh The pain builds up. The thing is, the stones can't cause pain in the ureters. What you are feeling is pain from the urine backing up in the kidneys--the pain develops as the kidneys produce urine that can't drain. I first felt my most recent kidney stone when I was on a mountaintop 5 miles from my car (and nearly 3,000' above, also.) I hiked out without a problem. $\endgroup$ Sep 5 '21 at 3:05
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    $\begingroup$ @uhoh Even when the pain was bad I would have preferred to hike out than be carried out. Unlike the standard presentation, kidney stones make me very sensitive to jolts. $\endgroup$ Sep 6 '21 at 1:10
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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 North America and Europe, the annual number of new cases per year of kidney stones is roughly 0.5%.

If there are 2000 astronauts staying half a year for each one at the ISS, we may expect only 5 cases of kidney stones. But it would take 125 years with 8 astronauts at ISS to observe theses 5 cases.

If there would 4 or 6 cases instead of 5, we can't tell if the rate of kidney stones in space increases, decreases or doesn't change in space.

Using the medical data of all ISS astronauts, even a tenfold increase of the rate of kidney stones could not be detected.

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  • $\begingroup$ Is that kind of medical data public? $\endgroup$ Sep 3 '21 at 16:37

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