Purpose Fragments 4 mm or smaller after ureteroscopy historically have been considered clinically insignificant but there is a reported 20% event rate on followup even with stones 4 mm or smaller. In this study we examine the natural history, complications and re-intervention rates of fragments after ureteroscopy. Materials and Methods Data from 6 centers were collected retrospectively from members of the Endourology Disease Group for Excellence in 232 patients who had residual fragments after ureteroscopy between 2006 and 2013. Patients with fragment(s) of any size on imaging within 12 months were eligible. The primary outcome measured was stone events, and secondary outcomes included stone growth, stone passage, re-intervention and complications. Results Of the 232 subjects with fragments 131 (56%) required no further intervention and remained asymptomatic, 34 (15%) experienced complications requiring no intervention and 67 (29%) required intervention, ie the primary outcome stone event rate was 44%. Fragments larger than 4 mm were more likely to grow with time (p <0.001) and were associated with more complications (p=0.039). Fragments larger than 2 mm were more likely to grow (p <0.001) but were not associated with complications or re-intervention. Re-intervention was predictable based on fragment size (p=0.017). In a multivariable logistic regression model there was no significant difference between the techniques of dusting stones or basket extraction. Conclusions This study suggests that fragment size larger than 4 mm after ureteroscopy is associated with significantly higher rates of stone growth, complications and the need for re-intervention. Ensuring complete stone-free status is the most effective strategy to reduce stone events after ureteroscopy.
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