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Abstract
Background: The formation of a renal stone during space flight may have serious negative
effects on the health of the crewmember and the success of the mission. Urinary biochemical
factors and the influence of dietary factors associated with renal stone development
were assessed during long duration Mir Space Station missions. Methods: Twenty-four-hour
urine samples were collected prior to, during and following long duration space flight.
The relative urinary supersaturation of calcium oxalate, calcium phosphate (brushite),
sodium urate, struvite and uric acid were determined. Results: Changes in the urinary
biochemistry of crewmembers during long duration spaceflight demonstrated increases
in the supersaturation of the stone-forming salts. In-flight hypercalciuria was evident
in a number of individual crewmembers and 24-hour dietary fluid intake and urine volume
were significantly lower. During flight, there was a significant increase in brushite
supersaturation. Conclusions: These data suggest acute effects of space flight and
postflight changes in the urinary biochemistry favoring increased crystallization
in the urine. The effects of dietary intake, especially fluid intake, may have a significant
impact on the potential for renal stone formation. Efforts are now underway to assess
the efficacy of a countermeasure to mitigate the increased risk.