title: Changes in urine parameters after desert exposure: assessment of stone risk in United States Marines transiently exposed to a desert environment.
abstract: OBJECTIVE
  Living in a desert environment has been associated with a higher incidence of kidney stone formation, likely because of concentrated urine output, higher production of vitamin D and genetic predisposition. We determined the changes in urinary parameters after a group of United States Marines temporarily transitioned from a temperate environment to a desert environment.
  
  
  METHODS
  A total of 50 Marines completed a questionnaire and performed 3, 24-hour urine collections before mobilization to the desert, after 30 days in the desert and 2 weeks after returning from the desert.
  
  
  RESULTS
  Daily urine output decreased 68% to 0.52 L despite marked increased fluid intake (17 L per day). Total daily urinary excretion of calcium, uric acid, sodium, magnesium and potassium in the desert decreased by 70%, 41%, 53%, 22% and 36%, respectively. Urinary pH decreased from 6.1 to 5.6 while in the desert, and citrate and oxalate had minimal changes. After their return from the desert, apart from a decrease of 22% in oxalate, there were no statistically significant differences from baseline. While in the desert, relative supersaturation risks of uric acid and sodium urate were increased 153% and 56%, respectively. Brushite relative supersaturation decreased 24%. After their return there was no statistical difference from baseline.
  
  
  CONCLUSIONS
  Our findings suggest that the kidneys preserved water and electrolytes while the Marines were subjected to the desert environment. Despite this conservation, relative saturations indicate increased risk of stones in healthy men exposed to a desert environment with rapid resolution upon return.
authors.affiliation: Department of Urology, Naval Medical Center San Diego, San Diego, California 92124, USA. James.masterson@med.navy.mil
authors.forename: James H
authors.initials: JH
authors.lastname: Masterson
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Jourdain
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Collard
authors.forename: Chong H
authors.initials: CH
authors.lastname: Choe
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Christman
authors.forename: James O
authors.initials: JO
authors.lastname: L'Esperance
authors.forename: Brian K
authors.initials: BK
authors.lastname: Auge
mesh_terms: D000328:Adult; D003889:Desert Climate / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008889:Military Personnel; D018570:Risk Assessment; D014481:United States; D014556:Urine / Q000737:chemistry*; D055815:Young Adult