Cystine stones: A single tertiary center experience

Objective: To analyze the epidemiological and clinical characteristics and therapeutic outcomes of patients with cystine stones and to compare them with the characteristics of patients with calcium oxalate stones. Patients and Methods: We identified 30 patients with cystine stones who were consulted in our department from January 1972 until December 2013. These patients were matched and paired, based on age and gender, to 30 calcium oxalate stone formers who were diagnosed and treated in our department from January 2011 until December 2013. Results: Cystine stones were significantly large in size (p<0.001) and most of them were found in the kidney (p=0.002). Patients with cystinuria had their first stone episode at an early age (p<0.001) compared with patients with calcium oxalate stones. No significant differences were observed regarding the frequency and the severity of symptoms. Both groups had similar visits per year in outpatient clinics, emergency room admissions, and episodes of febrile urinary tract infections. Cystine stone formers had undergone significantly higher number of procedures for stone removal (p<0.001). No statistical differences were found in the compliance rates between the groups. Patients with cystine stones had significantly higher serum creatinine levels (p=0.005). Conclusions: Cystine stones present in an earlier age and have the likelihood to be large in size. Patients with cystine stones undergo a greater number of procedures, and they have a greater risk to develop chronic renal impairment.