Trends in urinary calculi composition from 2005-2015: a single-tertiary center study

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Epidemiological data indicate that urolithiasis is steadily increasing, but little research has compared trends in the concurrent presence of certain minerals in mixed stones. We aim to study the evolution of kidney stone composition and stone patient demographics in an attempt to understand the current determinants of urolithiasis in view of optimizing strategies for prevention of stone formation and recurrence.


This is an IRB-approved retrospective study of Northwestern Medicine patients who underwent percutaneous nephrolithotripsy or ureteroscopy from 2005 to 2015. Patient demographics and stone composition were retrieved via Northwestern Medicine Enterprise Data Warehouse. Stones were classified based on the mineral that comprised the largest percentage of the stone. The frequency of each stone type was compared over the ten-year period and between each distinct age group and sex. Mixed stones containing uric acid (UA) and calcium oxalate monohydrate (COM) were sub-analyzed. We used Chi-squared tests for categorical variables and logistic regression to assess trends for each stone type with year, sex, and age groups as covariates.


5,268 stones were treated from 2005-2015 of which only 12.0% were pure. COM was predominant in most age groups with the exception of 15-29 year olds where carbonate apatite (CA) and calcium oxalate dihydrate (COD) were more prevalent. The male/female ratio decreased significantly from 1.8 to 1.08 (p


In this 10-year span, the stone patient population has aged and became more gender-equal. This increase in female patients parallels the increase of female obesity in US. The paucity of pure stones and increasing predominance of COM, including when mixed with UA, suggest the need for a new type of management and prevention of urolithiasis.

Funding: None