Objectives: This study aimed to demonstrate the dominant role of metabolic disorders in the formation of calcium oxalate stones in patients with recurrent urolithiasis, as well as in patients experiencing their first episode of urolithiasis. Patients and Methods: The records of the patients who attended our kidney stone outpatient clinics between 2008 and 2012 were reviewed, and the data of 318 calcium oxalate stone patients who had undergone a metabolic assessment were retrospectively analysed. The patients were divided in two groups. The first group included the patients who presented with their first episode of urolithiasis (Group 1, n = 170), and the second group included patients with recurrent urolithiasis (Group 2, n = 148); intergroup comparisons of metabolic disorders were performed. Results: A significant difference was found between the two groups in mean urine calcium levels (Group 1, 0.25; Group 2, 0.31; p = 0.001); the mean serum calcium level was found to be significantly higher although at less extent in Group 2 (Group 1, 9.4; Group 2, 9.6); p = 0.04). Significant differences were also found in mean urine citrate (Group 1, 481.9; Group 2, 397.2, p < 0.0001) and oxalate levels (Group 1, 22.1; Group 2, 28.5; p < 0.0001) . Conclusions: This study revealed a metabolic tendency to hypercalciuria in calcium oxalate stone patients, predominantly in those with recurrent calcium oxalate urolithiasis. Urinary oxalate excretion was found to be higher in recurrent urolithiasis in comparison to the first episode of calcium oxalate urolithiasis and urinary citrate excretion lower in recurrent urolithiasis.
Kidney stone; Calcium oxalate; First episode; Recurrent