Temporal Changes in Kidney Stone Composition and in Risk Factors Predisposing to Stone Formation.
PURPOSE
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.


MATERIALS AND METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
['Xu|Li Hao Richie|LHR|', 'Adams-Huet|Beverley|B|', 'Poindexter|John R|JR|', 'Maalouf|Naim M|NM|', 'Moe|Orson W|OW|', 'Sakhaee|Khashayar|K|']
D000328:Adult D015984:Causality D005260:Female D006801:Humans D007669:Kidney Calculi D008297:Male D008875:Middle Aged D012189:Retrospective Studies D018570:Risk Assessment D012307:Risk Factors D013997:Time Factors
calcium uric acid hydrogen-ion concentration kidney calculi urine