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?