page_title: Renal stone formation in space
section_title: Causes
hierarchical_section_title: Renal stone formation in space / Causes and countermeasures / Causes
caption_attribution_description: English: This micrograph shows calcium oxalate crystals in urine. These small crystals can develop to form renal stones. The Renal Stone Risk During Space Flight experiment is conducted aboard the International Space Station. Image credit: NASA/JSC
context_page_description: Renal stone formation and passage during space flight can potentially pose a severe risk to crew member health and safety and could affect mission outcome. Although renal stones are routinely and successfully treated on Earth, the occurrence of these during space flight can prove to be problematic.
context_section_description: Several factors contribute to the formation of renal stones in space.  Dietary changes, bone metabolism, dehydration, increased salt intake as well as decreased urine volumes and increased urine saturation are all possible causes of renal stone formation.  It has been noted that spaceflight-induced changes in urine biochemistry are conducive for stone formation.
  Other possible causes include:
  increased urinary pH
  history of or predisposition to stone formation
  inflight food stability
  preservation of food using salt
  quantity of onboard water supply
  limited nutritional sources
  increased diet of animal protein
  The most common renal stone is calcium oxalate and is usually caused by treatable metabolic disorders of hypercalcuria (increased calcium levels in the urine).  These stones cause pain with passage and blockage and have been known to recur.
  Uric acid stones have similar characteristics as the calcium oxalate stones, but occur much more rarely (approximately 5% of all renal stones).  Since they are translucent, they cannot be seen by radiographs.
  Struvite stones are generated by infections of urease-containing microorganisms that are capable of hydrolyzing the urea in the urine to carbon dioxide and ammonia.  Struvite stones can form when urinary pH rises above 7.2, can fill the renal collection system, and can erode into the renal tissue.
  Cystine stones, caused by hereditary cystinuria, begin forming in childhood and can grow large enough to fill the renal collection system.
  Calcium phosphate stones, or otherwise called brushite, are caused by high urine pH and a supersaturation of calcium phosphate salt in the urine.
caption: This micrograph shows calcium oxalate crystals in urine. These small crystals can develop to form renal stones. The Renal Stone Risk During Space Flight experiment is conducted aboard the International Space Station.
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