Objectives
Renal stone formation is a common medical problem, which affects approximately 12-20% of all American men and 5-10% of women during their lifetimes. Approximately 70% of all renal stones are composed of calcium oxalate; the remaining 30% are composed of calcium phosphate, uric acid and struvite, and cystine stones. The physiological and environmental causes of renal stone formation are varied, although diet is a well known contributor to renal stone formation.
Exposure to the microgravity environment of space alters human physiology. A number of these changes are expected to contribute to an altered urinary environment that will in turn influence the potential for renal stone formation. The most obvious changes observed in astronauts are the increased excretion of calcium (Ca) and the negative calcium balance thought to be the result of bone loss. Other demonstrated changes include decreased urinary output, urinary pH, magnesium (Mg), and citrate concentrations and increased urinary phosphate. All of these changes are expected to increase the urinary supersaturation of renal stone-forming salts and increase the risk of renal stone formation.
Similar studies for the Space Shuttle program, with mission durations of 4-14 days, collected data from 150 astronauts. Those studies have shown that immediately postflight, the urine of most crewmembers is saturated with stone-forming salts. These crewmembers are at an increased risk for developing calcium oxalate and uric acid stones. Also, there was a difference in the values of astronauts flying on short missions (up to six days in space) and those with a longer exposure to microgravity (7 to 14 days), which led to the hypothesis that the risk of calcium oxalate stones increases as the length of the mission increases.
Shuttle-Mir Missions Approach
Additional information was gathered by keeping a log-book, recording food, fluid, and medication intakes, as well as exercise periods, to assess any environmental contributions to renal stone formation.
Results Publications Principal Investigators
German S. Arzamazov, M.D.
Mir-18
To assess the renal stone-forming potential, 24-hour urine collections were taken preflight, inflight and postflight. The collected urine are analyzed for total volume, pH, and the concentrations of stone-forming salts and substances, like calcium, calcium oxalate, uric acid, citrate, sodium, sulfate, phosphorus, magnesium, and potassium. From the measured concentrations, the relative urinary supersaturation can be calculated and renal stone risk can be estimated.
This investigation was part of the experiment program of five NASA missions onboard the Russian Space Station Mir. The data from the first three missions were analyzed, and the results indicate an increased risk for renal stone formation after long-term space flights. The excretion of urinary calcium is generally increased after long-term space flight, which is one of the key contributors to an increased risk of forming calcium containing stones.
None available at this time
Peggy A. Whitson, Ph.D.
NASA/Johnson Space Center
Institute of Biomedical Problems
 |
Curator:
Julie Oliveaux
Responsible NASA Official: John Uri |
Page last updated: 07/16/1999
.gif)