Interconversion of stone composition profiles from two recurrent stone episodes in stone formers.

BACKGROUND: The aim of the study was to investigate the interconversion of the stone chemical composition of two recurrent stone episodes in stone formers.

METHODS: The data of 1098 stones analyses from 549 patients with a history of two renal stone episodes were selected and reviewed. The stone composition between the two recurrent episodes of stones was compared.

RESULTS: The percent occurrences of stones caused by infection, known as infection stones, in new episodes of stones significantly increased by 7% and uric acid stones increased by 3.8% while the calcium oxalate stones decreased by 13.1% (each p<0.05). The mean recurrent interval of new episodes of stones was 34.2 months. Infection stones had a significant shorter interval time compared to calcium oxalate stones (p<0.001). On a patient-by-patient investigation, 32.9% of patients underwent conversions of stone compositions, with 31.9% and 34.1% in men and female, respectively (p=0.590). The mutual conversion of infection stones to calcium oxalate stones was most common. The 61.1% of patients with uric acid recurrent stones were composed of calcium oxalate in the previous episode of stones, and 5% and 51.7% of patients with infection stones developed stones of uric acid or calcium oxalate in the new episode, respectively.

CONCLUSIONS: Alterations of stone components during follow-up were found in as high as 32.9% of patients with no gender difference. The impetus of these shifts is not readily apparent. Accurate and repeated stone analyses throughout the course of recurrent stone disease are highly warranted, which may be useful to prevent recurrence of composition-specific stones.