The Renal Stone experiment tests the effectiveness of potassium citrate in preventing renal stone formation during long-duration spaceflight. Kidney stone formation, a significant risk during long missions, could impair astronaut functionality.Principal Investigator
Johnson Space Center, Human Research Program, Houston, TXSponsoring Agency
National Aeronautics and Space Administration (NASA)Expeditions Assigned
|3|4|5|6|8|11|12|13|14|Previous ISS Missions
Similar studies were conducted on Shuttle, including STS-107 (Columbia), which was lost in 2003. Renal Stone has been performed on ISS for Expeditions 3-6, 8 and 11-13.
The loss of calcium from bone combined with decreased fluid intake in flight increases the probability for kidney stone formation during and after flight. Development of a kidney (or renal) stone in an astronaut can have serious consequences since it cannot be treated in flight as it would be on the ground. Therefore, quantification of renal stone formation potential and recovery is necessary to reduce this risk. This study examinees the potential development of renal stones in space crews and the efficacy of a pharmaceutical countermeasure.
Potassium citrate (K-cit) is a proven ground-based treatment for patients suffering from renal stones. In this study, from three days before launch and continuing through 14 days after landing each crewmember takes either two K-cit tablets or two placebos daily. They collect urine samples during 24-hour periods when in flight, once at the beginning, midway point, and end of a mission. In addition to taking pills and collecting urine samples, crewmembers maintain handwritten logs of their daily food and fluid intake, exercise, and medication during the time of the urine collections. These log books act as a backup to the barcode reader records that are part of the inventory management system with which crews typically record food intake and medication.
Ultimately, these data will not only help long-duration space flight crews but also will aid those on Earth in understanding how renal stones form in otherwise healthy persons. This should also provide insight into stone-forming diseases on Earth.
Human exposure to microgravity results in a number of physiological changes. Among these are changes in renal function, fluid redistribution, bone loss, and muscle atrophy, all of which contribute to an altered urinary environment and the potential for renal stone formation during and immediately after flight. In-flight changes previously observed include decreased urine volume and urinary citrate and increased urinary concentrations of calcium and sodium. The formation of renal stones could have severe health consequences for crewmembers and negatively impact the success of the mission. This study will provide a better understanding of the risk factors associated with renal stone development during and after flight, as well as test the efficacy of potassium citrate as a countermeasure to reduce this risk.Earth Applications
Understanding how the disease may form in otherwise healthy crewmembers under varying environmental conditions will also provide insight into stone forming diseases on Earth.
All operational requirements are centered on crew participation. Each crew member will be assigned a pallet containing the pills and UCKs. They will use the Inventory Management System Barcode Reader to record their samples, food intake (food packets are marked with barcodes), and medication.
The samples will be returned to Earth and sent to the principal investigator (PI) for analysis. The PI will study the urine chemistry of the crew members to determine each individual's risk of renal stone formation, and compare the urine chemistry based on the crew member's medication and daily activities to determine what factors may have caused increases and decreases in stone-forming chemicals. The study will measure the total volume of urine voided by each crew member and the levels of chemicals associated with stones: calcium, oxalate, sodium, sulfate, phosphorus, magnesium, potassium, creatinine, uric acid, as well as pH balance.
Renal Stone is designed as a double-blind study. Each crew member will be assigned a blister packet of pills, but they will not know if their personal packet contains potassium citrate or placebos. Two pills are taken at dinner time. In addition to taking pills and collecting urine samples, the crew will maintain handwritten logs of their daily food and fluid intake, exercise, and medication. The log books will act as backup to the Barcode Reader records.
Urine samples were collected and analyzed before, during, and after flights, as was dietary information from crewmembers. Since the experiment design calls for the combination and comparative analysis of data from all Expeditions, final results are not yet available.