It is often assumed that stones remain similar in composition. However, the retrospective review by Siddiqui and associates demonstrated that stone composition might change in a significant proportion of patients (MP05-19).
Two hundred and seventy patients, representing 734 stones, who underwent repeat stone analyses over a 7-year period were evaluated for changes in stone composition. Stones were divided into 4 groups: calcium stones, uric acid stones, infection stones, and other (cystine and xanthine). Overall, 16% of patients demonstrated a change in stone composition at a mean time of 26 months. Uric acid stone formers were most likely to demonstrate a change in stone composition (43%), followed by infected stone formers (33%). Other stone formers and calcium stone formers were less likely to have compositional changes (13% and 8%, respectively). This is important because recurrent treatments are often impacted by presumed stone composition, especially as it pertains to uric acid stones, which are typically treated with urine alkalization.
Based on this study, the failure of therapy, especially medical therapy in uric acid patients, could be due to a change in the stone composition.
Presented by Mohummad Minhaj Siddiqui at the 29th World Congress of Endourology & SWL (WCE) - November 30 - December 3, 2011 - Kyoto International Conference Center - Kyoto, Japan
Reported for UroToday by Joseph Graversen, MD, Fellow Minimally Invasive Surgery and Endourology, University of California-Irvine Medical Center, Irvine, CA
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