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

The goal of this study was to investigate recent changes in stone composition and patient demographics to identify factors influencing stone formation for the purpose of reducing the incidence of urolithiasis and preventing stone recurrence. This retrospective analysis includes patients who underwent percutaneous nephrolithotripsy or ureteroscopy at our institution from 2005 to 2015. Northwestern Medicine Enterprise Data Warehouse was used to retrieve demographic information and stone composition analyses. The composition of mixed stones containing uric acid (UA) and calcium oxalate monohydrate (COM) was analyzed further. Chi-squared tests were used for categorical variables and logistic regression was used to assess trends. From 2005 to 2015, 5268 stones were treated. COM was predominant in 42.2% and only 16.6% were pure. The male/female ratio decreased significantly from 1.8 to 1.08 and patient age increased ( p < 0.001) with 45.6% of patients being 60 or older in 2015. Females formed more CO dihydrate (COD; p = 0.008) and struvite ( p = 0.001) overall. The incidence of COM ( p = 0.007) and UA ( p < 0.001) rose significantly in men whereas both sexes saw a decrease in carbonate apatite (CA; p < 0.001). COM increased considerably from 12 to 75% amongst mixed stones with UA over the 11-year span. We concluded that stone formers have become older and more gender-equal. The increase in female patients parallels the increase in female obesity in the US. The rising predominance of COM, including when mixed with UA, and the scarcity of pure stones indicates it may be necessary to develop new approaches to managing and preventing urolithiasis.