Beyond Calcium Stones: Predictors of Uric Acid and Struvite Urolithiasis Among Surgically Treated Patients in The Kumaun Himalayan Region

Background: Calcium stones dominate most urinary stone series, but uric acid and struvite stones require distinct metabolic and infection-focused preventive approaches. Identifying patient characteristics associated with these non-calcium phenotypes may support earlier targeted evaluation. The objective is to identify sociodemographic, environmental, and lifestyle characteristics associated with uric acid and struvite stones, using calcium stones as the reference phenotype, among surgically treated patients in the Kumaun Himalayan region. Material and Methods: This secondary analysis used aggregate data from a hospital-based cross-sectional study of 200 symptomatic patients with urolithiasis who underwent extracorporeal shock-wave lithotripsy, endoscopic surgery, or open surgery over 18 months. Retrieved stones were classified by qualitative chemical analysis as calcium, struvite, or uric acid. Global associations were reassessed using Pearson's chi-square test. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were calculated separately for struvite versus calcium and uric acid versus calcium; Fisher's exact test was used for pairwise comparisons. Results: Calcium stones accounted for 114 (57.0%) cases, uric acid stones for 47 (23.5%), and struvite stones for 39 (19.5%). Stone phenotype differed across age categories (P=0.002). Compared with patients aged 21–40 years, those aged 0–20 years had higher odds of struvite (OR 7.25; 95% CI 1.77–29.68) and uric acid stones (OR 4.83; 95% CI 1.23–19.04). Patients aged 61–80 years also had higher odds of struvite (OR 6.04; 95% CI 1.97–18.49) and uric acid stones (OR 4.03; 95% CI 1.38–11.74). Marital status showed a global association (P=0.014), but estimates for unmarried patients were imprecise because only 14 participants were unmarried. Sex, residence, education, smoking, family history, dietary pattern, alcohol use, and drinking-water source were not associated with stone phenotype. Conclusion: Age at both extremes emerged as the principal unadjusted predictor of non-calcium stone composition in this surgically treated cohort. The apparent association with unmarried status was based on sparse data and may reflect age confounding. Patient-level data and modern compositional analysis are required to validate independent predictors.

Keywords: Urolithiasis; uric acid stone; struvite; infection stone; stone composition; Himalaya; Uttarakhand.