Removal of Small, Asymptomatic Kidney Stones and Incidence of Relapse

N Engl J Med. 2022 Aug 11;387(6):506-513. doi: 10.1056/NEJMoa2204253.


Background: The benefits of removing small (≤6 mm), asymptomatic kidney stones endoscopically is unknown. Current guidelines leave such decisions to the urologist and the patient. A prospective study involving older, nonendoscopic technology and some retrospective studies favor observation. However, published data indicate that about half of small renal stones left in place at the time that larger stones were removed caused other symptomatic events within 5 years after surgery.

Methods: We conducted a multicenter, randomized, controlled trial in which, during the endoscopic removal of ureteral or contralateral kidney stones, remaining small, asymptomatic stones were removed in 38 patients (treatment group) and were not removed in 35 patients (control group). The primary outcome was relapse as measured by future emergency department visits, surgeries, or growth of secondary stones.

Results: After a mean follow-up of 4.2 years, the treatment group had a longer time to relapse than the control group (P<0.001 by log-rank test). The restricted mean (±SE) time to relapse was 75% longer in the treatment group than in the control group (1631.6±72.8 days vs. 934.2±121.8 days). The risk of relapse was 82% lower in the treatment group than the control group (hazard ratio, 0.18; 95% confidence interval, 0.07 to 0.44), with 16% of patients in the treatment group having a relapse as compared with 63% of those in the control group. Treatment added a median of 25.6 minutes (interquartile range, 18.5 to 35.2) to the surgery time. Five patients in the treatment group and four in the control group had emergency department visits within 2 weeks after surgery. Eight patients in the treatment group and 10 in the control group reported passing kidney stones.

Conclusions: The removal of small, asymptomatic kidney stones during surgery to remove ureteral or contralateral kidney stones resulted in a lower incidence of relapse than nonremoval and in a similar number of emergency department visits related to the surgery. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and the Veterans Affairs Puget Sound Health Care System; number, NCT02210650.).

Publication types

  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Chronic Disease
  • Endoscopy* / statistics & numerical data
  • Humans
  • Incidence
  • Kidney Calculi* / epidemiology
  • Kidney Calculi* / surgery
  • Recurrence
  • Secondary Prevention*
  • Ureteral Calculi* / epidemiology
  • Ureteral Calculi* / surgery
  • Ureteroscopy

Associated data