101 Archivio Italiano di Urologia e Andrologia 2016; 88, 2 ORIGINAL PAPER Metabolic assessment of recurrent and first renal calcium oxalate stone formers Basri Çakırog ˘lu 1 , Erkan Eyyupog ˘lu 2 , Aydin Ismet Hazar 3 , Bekir Sami Uyanik 4 , Barıs ¸ Nuhog ˘lu 3 1 Department of Urology, Hisar Intercontinental Hospital, Umraniye, Istanbul, Turkey; 2 Department of Urology, Amasya Sabuncuog ˘lu Serefeddin Training and Research Hospital, Amasya, Turkey; 3 Department of Urology, Taksim Training and Research Hospital, Gaziosmanpasa, Turkey; 4 Department of Clinical Biochemistry, Hisar Intercontinental Hospital, Umraniye, Istanbul, Turkey. Objectives: This study aimed to demon- strate the dominant role of metabolic dis- orders 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 pre- sented with their first episode of urolithiasis (Group 1, n = 170), and the second group included patients with recur- rent 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 differ- ences 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, predomi- nantly in those with recurrent calcium oxalate urolithiasis. Urinary oxalate excretion was found to be higher in recur- rent urolithiasis in comparison to the first episode of calcium oxalate urolithiasis and urinary citrate excretion lower in recurrent urolithiasis. KEY WORDS: Kidney stone; Calcium oxalate; First episode; Recurrent. Submitted 18 June 2015; Accepted 4 December 2015 Summary No conflict of interest declared. occur within the first five years after the first episode of urolithiasis (1). Calcium oxalate stones (CaOx) are the most common type of urinary stones (60% pure calcium oxalate stones and 20% mixed stones) (2, 3). We decid- ed to analyse the metabolic states of our patients with CaOx urolithiasis since our sample size was adequate to have a significant evaluation. Urine volumes and urine components both give an indication about the health of the kidneys and constitute a collective indicator of com- plex body functions, all interacting with each other. Therefore, we tried to achieve an understanding about the metabolism of the patients who presented with a first episode of urolithiasis and with recurrent CaOx urolithi- asis by interpreting their 24-hour urine analyses (2, 3-5). MATERIALS AND METHODS Study population The admissions/follow-up records of 3,500 patients who attended two different kidney stone outpatient clinics of two different Departments of Urology between 2008 and 2012 were reviewed in order to achieve an adequate sample size to investigate any differences between the patients who presented with the first episode of urolithi- asis and patients with recurrent urolithiasis, regarding metabolic abnormalities underlying idiopathic CaOx stones. A total of 2,653 cases at the first episode and 847 cases of recurrent urolithiasis were identified. Stone analyses were performed using a Fourier Transform Computed Infrared (FT-IR) Spectrometer. CaOx stones (including monohydrate and dehydrate calcium oxalate, pure or mixed wirh apatite) were detected in 176 patients who experienced their first episode of urolithia- sis and in 210 patients with recurrent urolithiasis. Anamnesis, past medical history, previous surgery, and medication use that had been recorded in the patient files were reviewed in terms of exclusion criteria. Exclusion criteria included age younger than 18 years; missing height and weight data; use of thiazide, tri- amterene, or loop diuretics; use of potassium or potassi- um citrate; use of other antihypertensive agents; dia- betes, hyperlipidemia, coronary heart disease, stroke, or DOI: 10.4081/aiua.2016.2.101 INTRODUCTION Today, about 10% of the male population and 5% of the female population suffer from kidney stone disease, which is more prevalent between 30 to 40 years of age. The recurrence rate in patients who recover from a firs kidney stone episode, either spontaneously or through intervention, was found to be about 4% to 5% per year; based on this percentage, the cumulative rate of recur- rence will be 75% within 20 years. Most recurrences