Variations in Renal Tract Calculus Composition Between South Asian and Non-South Asian Ethnicities in North West England

Introduction Ethnic variations in renal tract calculus composition remain poorly understood, despite an increasing global burden of urolithiasis. This study aimed to investigate differences in stone composition between South Asian and non-South Asian populations in North West England. Methods A retrospective cohort study was conducted using data from three NHS Hospital Trusts over five years (2015-2020). Stone composition analysis of 2,131 calculi from 1,890 patients categorised the data into five groups: calcium oxalate, mixed calcium oxalate and uric acid, uric acid, calcium phosphate and mixed calcium oxalate and calcium phosphate. Multivariate binary logistic regression assessed the relationship between ethnicity and stone composition. Results South Asian ethnicity was significantly associated with a higher likelihood of forming mixed calcium oxalate and uric acid calculi (odds ratio {OR}, 2.903; p = 0.017) and a decreased likelihood of calcium phosphate calculi (OR, 0.461; p = 0.025) compared to other ethnicities. Ethnicity was not significantly associated with other stone types. Additionally, male sex and increased age were significant predictors of specific stone compositions. Conclusion South Asian patients demonstrated distinct patterns of renal stone composition, being more likely to form mixed calcium oxalate and uric acid calculi and less likely to develop calcium phosphate stones. These findings indicate an association between ethnicity and stone composition but do not imply causation. Further prospective studies incorporating dietary, metabolic and biochemical data are warranted to clarify the mechanisms underlying these differences and their potential clinical relevance.