The long-term outcome of cystinuria in Japan.

Recurrence of growth of urinary stone is frequently observed during the clinical course of cystinuria patients. The aim of the present study is to examine the long-term outcome of cystinuria in Japan and clarify the effects of medical treatment on urinary stone. Thirty-one patients with cystinuria who had been followed up longer than 6 months were included. The follow-up period was 6-264 months with a mean of 89.5 months. Stone event was defined as appearance of new stone or radiological evidence of stone growth. All patients were managed with forced hydration and urine alkalization. Twenty-eight patients were treated with administration of thiol such as D-penicillamine or alpha-mercaptopropionylglycine. Stone events per year ranged from 0 to 1.09 with a median of 0.09. Stone events per patient-year was 0.19 for all patients. The average urinary cystine concentration during treatment in the favorable outcome group (stone events per year < 0.3) was lower that that in the unfavorable outcome group (stone events per year >/=0.3); 221.2 +/- 75.2 vs. 303.3 +/- 93.5 mg/l, although the difference was not statistically significant. Prognosis of urinary stone in Japanese patients with cystinuria was relatively good with large variation. The medical treatment to reduce urinary cystine concentration would be useful for the management of cystinuria.