Findings From 9 Years of Renal Stone Surveillance of U.S. Astronauts

INTRODUCTION: Renal stones are thought to be a risk for spaceflight due to urine chemistry changes, induced by microgravity. Asymptomatic stone can have significant medical and mission impact.For9 years astronauts travelling to the International Space Station (ISS) have received pre-and post-flight renal ultrasound, according to a specialized renal ultrasound protocol, to look for renal calcifications or mineralized renal material (MRM).A new ultrasound machine was put in service halfway through the screening program. METHODS: MRM screening data from pre-and post-flight were compared, to look for changes in MRM burden. Pre-and post-flight scans from 42 subjects were compared. Studies were further stratified by old versus new machine. Measures were modeled using the analysis of variance (ANOVA) as defined by the interaction between pre-to postflight, and machine-to-machine. RESULTS: There was no observed statistical change seen in MRM burden pre-to postflight using the new higher-resolution ultrasound machine. DISCUSSION: The new machine gives more precise measurements and allows us to differentiate MRMs from other bright objects seen on ultrasound, such as small blood vessels. These data imply that spaceflight does not increase the risk of renal stone formation, at least out to the length of ISS missions. This data will be used to update NASA’s Human System Risk Board’s risk tracking documents, in-flight Concept of Operations, and our Clinical Practice Guideline.