title: Temporal Changes in Kidney Stone Composition and in Risk Factors Predisposing to Stone Formation.
abstract: The prevalence of kidney stones has increased globally in recent decades. However, studies investigating the association between temporal changes in the risk of stone formation and stone types are scarce. We investigated temporal changes in stone composition, and demographic, serum and urinary parameters of kidney stone formers from 1980 to 2015.
  
  
  
  We retrospectively analyzed the records of 1,516 patients diagnosed with either calcium or uric acid stones at an initial visit to a university kidney stone clinic from 1980 to 2015.
  
  
  
  From 1980 to 2015, the proportion of uric acid stones in all stone formers increased from 7% to 14%. While age and body mass index increased with time in both uric acid and calcium stone formers, uric acid stone formers were consistently older and had a higher body mass index and lower urinary pH than calcium stone formers. The proportion of females with stones has increased over time but the increase in female gender was more prominent among calcium stone formers. Urinary pH, phosphorus, oxalate and sodium increased with time in calcium stone formers but remained unchanged in uric acid stone formers. After accounting for various parameters of stone risk, the strongest clinical discriminant of uric acid vs calcium stones was urinary pH. Limitations of this study include the retrospective single center design and the available number of patients with stone analysis.
  
  
  
  From 1980 to 2015, the proportion of uric acid stones increased significantly. With time, there were proportionately more female calcium stone formers but not uric acid stone formers. Urinary pH is the most prominent factor distinguishing uric acid from calcium stones.
authors.affiliation: Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Li Hao Richie
authors.initials: LHR
authors.lastname: Xu
authors.affiliation: Department of Clinical Science, University of Texas Southwestern Medical Center, Dallas, Texas; Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Beverley
authors.initials: B
authors.lastname: Adams-Huet
authors.affiliation: Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: John R
authors.initials: JR
authors.lastname: Poindexter
authors.affiliation: Division of Mineral Metabolism, University of Texas Southwestern Medical Center, Dallas, Texas; Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Naim M
authors.initials: NM
authors.lastname: Maalouf
authors.affiliation: Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; Division of Mineral Metabolism, University of Texas Southwestern Medical Center, Dallas, Texas; Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Orson W
authors.initials: OW
authors.lastname: Moe
authors.affiliation: Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; Division of Mineral Metabolism, University of Texas Southwestern Medical Center, Dallas, Texas; Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas. Electronic address: Khashayar.sakhaee@utsouthwestern.edu.
authors.forename: Khashayar
authors.initials: K
authors.lastname: Sakhaee
mesh_terms: D000328:Adult; D015984:Causality; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry* / Q000175:diagnosis / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors
keywords: calcium; hydrogen-ion concentration; kidney calculi; uric acid; urine