Small, asymptomatic kidney stones (≤6 mm) are often observed during removal of symptomatic stones, and no clear indications are provided by current guidelines on the need to remove these small stones, owing to a lack of prospective studies. In a multicentre, prospective, randomized trial, 75 patients who were scheduled to undergo endoscopic removal of primary stones were randomized 1:1 to receive or not receive surgical removal of small (secondary) kidney stones (treatment and control group, respectively), and the results were published in the New England Journal of Medicine. The primary outcome was relapse, measured as emergency department visits, subsequent surgery to remove stones or growth of secondary stones. At a mean follow-up time of 4.2 years, the cumulative incidence of relapse was higher in the treatment group than in untreated patients (P < 0.001 by log-rank test), and the restricted mean time to relapse was longer in patients from the treatment group than in patients who did not undergo removal of secondary stones (1,631.6 ± 72.8 versus 934.2 ± 121.8 days). Relapse occurred in 16% and 63% of patients from the treatment and control groups, respectively. Removal of secondary stones resulted in a median additional surgery time of 25.2 minutes. No increase in emergency department visits within 2 weeks (13% versus 11%) or in self-reported stone passage (21% versus 29%) was observed in patients undergoing removal of secondary stones compared with patients from the untreated group. Overall, results from this trial support the removal of small, asymptomatic kidney stones. The costs of additional surgery time are estimated to be much lower than the costs of subsequent surgery and/or emergency visits for patients who undergo relapse. The authors highlighted some limitations of the study, including the relatively small size and the presence of few non-white patients, but results from this trial highlight the benefit of removing secondary stones, filling a gap in the field.

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