Inconsistency in stone composition among bilateral urolithiasis patients: a multicenter retrospective study

The treatment or prevention strategies vary for different stone compositions. The current guidelines lack specific recommendations for composition analysis in bilateral urolithiasis due to limited data on the analysis of bilateral urinary stone composition. We aimed to calculate the prevalence of discordant stone compositions among bilateral urolithiasis patients, and identify factors associated with the discordance. We retrospectively enrolled 845 bilateral urolithiasis patients across seven centers in China, whose stones on both sides were analyzed separately for stone composition. We calculated the percent prevalence of discordant stone compositions among bilateral urolithiasis patients. Univariate analyses and multivariate logistic regression analyses were used to identify factors associated with this discordance. A total of 24.9% of enrolled patients had discordant stone compositions of bilateral uroliths, which ranged from 17.5 to 32.4% in the seven institutions. Among the 210 patients with discordant stone compositions, the two most common composition combinations were calcium oxalate/carbapatite (51.0%) and calcium oxalate/uric acid (35.7%). Four clinical variables, including sex, age, predominant component of calcium oxalate on one side, and predominant component of uric acid on one side, were associated with a stone composition inconsistency among bilateral urolithiasis in the multivariate logistic analyses. Notably, the pretreatment urinalysis results and preoperative serum biochemical parameters were not related to the stone composition inconsistency. Approximately one-quarter of the patients were identified as discordant stone formers among the bilateral urolithiasis patients in our study, highlighting the importance of separately analyzing the stone composition on both sides in patients with bilateral urolithiasis.