Analysis of clinical and laboratory findings affecting renal functions in patients followed for cystine stone disease

Objective: Cystine stones appear at an early age, recur frequently, and may require multiple surgical interventions. Recurrent stone attacks in these patients can negatively impact long-term renal function. The aim of this study was to analyze the clinical, biochemical, and laboratory findings affecting renal function in patients monitored for cystine stones and to evaluate the relationship between these factors and the development of renal dysfunction. Materials and Methods: This study was conducted by retrospectively reviewing the data of 39 patients diagnosed with cystinuria at the Gaziantep University Faculty of Medicine, Department of Urology, between 2018 and 2023, who had at least three years of regular follow-up. Patient demographics, number and type of surgery, and medical treatment were recorded. Laboratory data included creatinine, eGFR, urea, uric acid, electrolytes, parathyroid hormone, and vitamin D levels, as well as 24-hour urine cystine, citrate, and oxalate levels. Results: While the patients' mean eGFR was 129.05 mL/min/1.73 m² at initial presentation, it decreased to 95.95 mL/min/1.73 m² at final follow-up (p<0.05). Similarly, serum creatinine levels increased from 0.6 mg/dL to 0.93 mg/dL (p<0.05). In our study, eGFR values were significantly higher and creatinine levels were lower in patients receiving tiopronin therapy. Conclusion: The findings of this study indicate that renal dysfunction develops over time in patients with cystinuria. It can be said that the deterioration in renal function slows down in patients receiving tiopronin. It is believed that long-term renal function can be preserved with early diagnosis, adequate fluid intake, urine alkalization, and medical treatment. Keywords: metabolic analysis, renal function, cystinuria, tiopronin