What Lies Beneath the Stone? Metabolic Insights from Composition-Based Analysis of Kidney Stones

Background: Kidney stone disease is a complex disorder characterized by various metabolic disturbances. Although the analysis of stone composition offers essential etiological insights, its integration with 24-hour urinary and serum biochemical profiles is not fully utilized in formulating individualized prevention strategies. Methods: This retrospective study assessed patients diagnosed with nephrolithiasis, whose stone samples were analyzed using Fourier Transform Infrared (FTIR) spectroscopy. The samples were categorized into five distinct groups: calcium oxalate monohydrate (COM), calcium oxalate dihydrate (COD), calcium/magnesium phosphate (CaP), uric acid, and cystine. The study compared demographic data, recurrence status, serum parameters (calcium, uric acid, creatinine), and 24-hour urinary values (volume, calcium, oxalate, citrate, magnesium, phosphate, pH, sodium, and potassium) across these groups. Statistical analyses included ANOVA, Kruskal–Wallis, and chi-square tests. Results: In total, 506 patients were included in this study. The most common stone type was COD (60.7%), followed by COM (23.1%), CaP (9.1%), uric acid (6.1%), and cystine (1.0%). Uric acid stone formers were significantly older and had the lowest urinary pH (p < 0.001), whereas CaP stone formers had the most alkaline urine. Serum calcium levels were significantly higher in the COM group (p < 0.001) and serum uric acid levels were elevated in patients with uric acid stones (p < 0.001). Hypocitraturia and low urine volume were the most frequent metabolic abnormalities in all the groups. The highest recurrence rates were observed in the cystine (100%) and uric acid (81%) groups. Conclusion: The composition of kidney stones is significantly correlated with specific metabolic abnormalities. Uric acid stones are linked to low urinary pH and hyperuricemia, while calcium oxalate monohydrate (COM) stones are often associated with elevated serum calcium levels. These findings underscore the importance of composition-guided metabolic evaluations in informing personalized prevention strategies and reducing recurrence.