title: Stone composition as a function of age and sex.
abstract: OBJECTIVE
  Kidney stones are heterogeneous but often grouped together. The potential effects of patient demographics and calendar month (season) on stone composition are not widely appreciated.
  
  
  METHODS
  The first stone submitted by patients for analysis to the Mayo Clinic Metals Laboratory during 2010 was studied (n=43,545). Stones were classified in the following order: any struvite, any cystine, any uric acid, any brushite, majority (≥50%) calcium oxalate, or majority (≥50%) hydroxyapatite.
  
  
  RESULTS
  Calcium oxalate (67%) was the most common followed by hydroxyapatite (16%), uric acid (8%), struvite (3%), brushite (0.9%), and cystine (0.35%). Men accounted for more stone submissions (58%) than women. However, women submitted more stones than men between the ages of 10-19 (63%) and 20-29 (62%) years. Women submitted the majority of hydroxyapatite (65%) and struvite (65%) stones, whereas men submitted the majority of calcium oxalate (64%) and uric acid (72%) stones (P<0.001). Although calcium oxalate stones were the most common type of stone overall, hydroxyapatite stones were the second most common before age 55 years, whereas uric acid stones were the second most common after age 55 years. More calcium oxalate and uric acid stones were submitted in the summer months (July and August; P<0.001), whereas the season did not influence other stone types.
  
  
  CONCLUSIONS
  It is well known that calcium oxalate stones are the most common stone type. However, age and sex have a marked influence on the type of stone formed. The higher number of stones submitted by women compared with men between the ages of 10 and 29 years old and the change in composition among the elderly favoring uric acid have not been widely appreciated. These data also suggest increases in stone risk during the summer, although this is restricted to calcium oxalate and uric acid stones.
authors.affiliation: Division of Nephrology and Hypertension, Department of Internal Medicine, Department of Laboratory Medicine and Pathology, Lieske.John@mayo.edu.
authors.forename: John C
authors.initials: JC
authors.lastname: Lieske
authors.affiliation: Division of Nephrology and Hypertension, Department of Internal Medicine, Division of Epidemiology, Department of Health Sciences Research.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Rule
authors.affiliation: Department of Urology, and.
authors.forename: Amy E
authors.initials: AE
authors.lastname: Krambeck
authors.affiliation: Department of Anatomy and Cell Biology, Indiana University/Purdue University School of Medicine, Indianapolis, Indiana.
authors.forename: James C
authors.initials: JC
authors.lastname: Williams
authors.affiliation: Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, Minnesota; and.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Bergstralh
authors.affiliation: Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, Minnesota; and.
authors.forename: Ramila A
authors.initials: RA
authors.lastname: Mehta
authors.affiliation: Department of Laboratory Medicine and Pathology.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Moyer
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002129:Calcium Oxalate / Q000032:analysis; D002130:Calcium Phosphates / Q000032:analysis; D002648:Child; D002675:Child, Preschool; D003553:Cystine / Q000032:analysis; D017886:Durapatite / Q000032:analysis; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007669:Kidney Calculi / Q000737:chemistry*; D017616:Magnesium Compounds / Q000032:analysis; D008297:Male; D008875:Middle Aged; D010710:Phosphates / Q000032:analysis; D012621:Seasons; D012737:Sex Factors; D000069877:Struvite; D014481:United States; D014527:Uric Acid / Q000032:analysis; D055815:Young Adult
chemical_list: D002130:Calcium Phosphates; D017616:Magnesium Compounds; D010710:Phosphates; D002129:Calcium Oxalate; D014527:Uric Acid; D003553:Cystine; D017886:Durapatite; D000069877:Struvite; C494366:calcium phosphate, dibasic, dihydrate
keywords: calcium oxalate; calcium phosphate; infrared spectroscopy; struvite; uric acid