Metabolic Differences in 24-Hour Urine Parameters Between Calcium Oxalate Monohydrate and Dihydrate Kidney Stones: A Clinical Study

<b>Background:</b> Different types of kidney stones are associated with distinct changes in urine chemistry. <b>Methods:</b> We assessed urinary parameters of 98 patients with calcium oxalate (CaOx) stones one month following endoscopic stone removal. The 24 h urine analysis encompassed the assessment of various parameters, including volume, sodium, chloride, sulfate, nitrate, fluoride, phosphate, calcium, potassium, magnesium, oxalate, uric acid, citrate, creatinine, and pH levels. <b>Results:</b> Hypocitraturia was the most prevalent urinary abnormality (61.2%, <i>n</i> = 63), followed by low urine volume (53%, <i>n</i> = 52) and hypercalciuria (50%, <i>n</i> = 49). We did not find any statistically significant differences between patients with whewellite (COM) (<i>n</i> = 69) and weddellite (COD) stones (<i>n</i> = 29) (<i>p</i> > 0.05). However, oxalate concentration was the only parameter with a statistically significant intergroup difference (<i>p</i> = 0.0297). Additionally, in univariate linear regression analysis, urinary phosphate levels ≥ 48.0 mmol/d showed a trend towards significance (OR 0.17, 95% CI 0.02-1.15, <i>p</i> = 0.0692), indicating that phosphaturia is associated with a significant increase in the odds ratio of COD stones. To further explore metabolic heterogeneity among stone formers, we conducted cluster analysis, which revealed three distinct metabolic subgroups. Cluster 1 was predominantly associated with COM stones (80.5%) and exhibited significantly higher urinary excretion of sodium, calcium, oxalate, phosphate, and uric acid compared to Cluster 2, which had a more balanced distribution of monohydrate and dihydrate stones. <b>Conclusions:</b> These findings suggest that a specific metabolic phenotype may be linked to COM stone formation, providing a framework for risk stratification and personalized prevention strategies in calcium oxalate stone formers.