title: Conversion of calcium oxalate to calcium phosphate with recurrent stone episodes.
abstract: OBJECTIVE
  We have extended our previous observation that the percent occurrence of calcium oxalate stones decreased while that of calcium phosphate stones increased with each new stone event.
  
  
  METHODS
  The National VA Crystal Identification Center has analyzed veteran patient urinary tract stones from VA hospitals throughout the United States since 1983. We reviewed the composition of 33,198 stones with emphasis on the changes in composition. More than 11,786 stones came from 5,088 recurrent stone formers. Stones were analyzed using high resolution x-ray powder diffraction and Fourier transform infrared spectroscopic techniques. When the stones were investigated as a function of time, it was determined that there was greater variability when samples were more than 30 days apart.
  
  
  RESULTS
  The percent occurrence of whewellite, weddelite, apatite, brushite and uric acid in stones increased between 1.0% and 5.9% since our previous study. The percent occurrence of struvite decreased by 2.6%. The percent of calcium oxalate stones decreased while that of calcium phosphate stones increased with each new event. However, the total percent occurrence of all calcium containing stones did not significantly change with recurrent stone events.
  
  
  CONCLUSIONS
  Our study suggests a strong trend for the conversion of stone disease from calcium oxalate to calcium phosphate containing stones, which could influence the progression and severity of disease.
authors.affiliation: Medical College of Wisconsin, Clement J. Zablocki VA Medical Center, Milwaukee, Wisconsin 53295, USA.
authors.forename: Neil
authors.initials: N
authors.lastname: Mandel
authors.forename: Ian
authors.initials: I
authors.lastname: Mandel
authors.forename: Kathy
authors.initials: K
authors.lastname: Fryjoff
authors.forename: Tammy
authors.initials: T
authors.lastname: Rejniak
authors.forename: Gretchen
authors.initials: G
authors.lastname: Mandel
mesh_terms: D001031:Apatites / Q000032:analysis; D002129:Calcium Oxalate / Q000032:analysis*; D002130:Calcium Phosphates / Q000032:analysis*; D006801:Humans; D017616:Magnesium Compounds / Q000032:analysis; D010710:Phosphates / Q000032:analysis; D012008:Recurrence; D017550:Spectroscopy, Fourier Transform Infrared; D000069877:Struvite; D014527:Uric Acid / Q000032:analysis; D014545:Urinary Calculi / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D001031:Apatites; D002130:Calcium Phosphates; D017616:Magnesium Compounds; D010710:Phosphates; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; C016189:whewellite; D002129:Calcium Oxalate; D014527:Uric Acid; C485838:calcium phosphate, monobasic, anhydrous; C016188:weddellite; C020243:calcium phosphate; D000069877:Struvite; C485829:calcium phosphate, dibasic, anhydrous