Asymptomatic renal stones are commonly detected incidentally with more ubiquitous use of imaging in medicine today.¹ They pose an important issue that should rely on shared decision-making with the patient, weighing the morbidity of surgery with the potential for future symptomatic disease. Surgical treatment of asymptomatic stones may benefit the patient by avoiding future symptomatic progression or stone growth that may lead to emergency department (ED) visits or inconvenient need for urgent surgical intervention.² In some patients there can be associated anxiety and concern over potential acute progression to a symptomatic event, which would favor early surgical intervention. However, in some patients observation of asymptomatic renal stones may be favored due to low likelihood of need for future surgical intervention due to stone location or small size, patient comorbidities that increase risk of surgery, stability of stone over long period of observation, or patient preference due to asymptomatic nature.³ Ultimately, both observation and surgical treatment are acceptable options in most cases of asymptomatic nonobstructing renal stones.^2,3 Review of the current evidence will facilitate patient counseling to make the best decision for the individual patient.

Evidence to date has largely been retrospective with small cohorts and short follow-up periods. However, recently, Sorensen et al performed a randomized controlled trial comparing the treatment of small (≤6 mm) asymptomatic stones (secondary) via ureteroscopy at the time of treatment for primary ureteral or contralateral kidney stones (N=38) vs observation (N=35) with a mean follow-up of 4.2 years.⁴ This study included both ipsilateral and contralateral secondary asymptomatic stones. The primary outcome was relapse, which they characterized as stone growth on imaging (>1 mm), ED visits (trial side), or subsequent surgery of secondary stones.⁴ They found that the treatment group had significantly fewer relapses (16%) compared to the control group (63%; hazard ratio 0.18; 95% confidence interval 0.07 to 0.44) over 4 years with a minimal increase in median operative time of 25.6 minutes (IQR, 18.5 to 35.2).⁴ This new evidence clearly shows the benefit of treating secondary small asymptomatic renal stones for those already undergoing surgical intervention for primary stones that are either symptomatic or determined to be at high risk of causing a symptomatic event.

Treatment of contralateral asymptomatic stones with single-session bilateral surgery may require additional consideration. Several studies have shown the safety of single-session bilateral surgery; however, one should weigh the risks, including the potential for 2 ureteral stents, secondary procedures, increased surgical time depending on stone size, and increased risk of morbidity for more comorbid patients. Certainly, it is beneficial if the bilateral surgery can be safely done in 1 session; however, the question remains if the findings from the Sorensen et al study can be applied to larger stones.⁴ They showed a minimal increase in operative time; however, the median stone size of the secondary asymptomatic stones was 3 mm in the treatment group (IQR 3-4) and 4 mm in the control group (2-4). We know that prolonged operative time is associated with increased risk of complications, and if the overall surgery time expected is greater than 90 minutes (due to overall stone size or other factors), consideration for a staged approach should be given.⁵ In addition, Li et al performed a retrospective study looking at the concurrent treatment of contralateral asymptomatic renal stones (either single session or staged) and found no difference in the need for future surgical interventions at 2 years for stones ≤6 mm, suggesting that observation is also reasonable within that time frame.⁶ The question then arises, how small is too small a secondary stone size to consider contralateral surgery? In other words, should we be doing bilateral surgery on the contralateral side for punctate stones? Often these can be Randall’s plaques instead of treatable stones, which are difficult to distinguish on imaging.

One should also consider the high rate of residual stones after surgery; thus, surgery doesn’t always rid the patient of small asymptomatic stones.⁷ This is important to discuss with patients to manage expectations. Previous studies suggest that there is potentially a higher risk of adverse stone events in patients with asymptomatic residual fragments following surgery compared to those with untreated asymptomatic renal stones, since the residual fragment will likely become detached after treatment.

The last consideration is that most of the studies evaluating the treatment or observation of asymptomatic renal stones have only included traditional measurements of success, such as a reduction in ED visits, clinical progression to symptomatic disease, and need for future surgical intervention. There is value added in also including patient-reported outcome measurements such as health-related quality of life that may aid clinicians to better discuss the goals of treatment and improve the definition of success.⁸

Overall, urologists need to look to their patients for input to individualize treatment decisions through shared decision-making for asymptomatic kidney stones and use the evidence to help guide the conversation. Consider the goals of treatment and take into account patient preference to optimize quality of life, in addition to traditional stone and patient factors. It is important to discuss and set realistic patient expectations, especially in the case of the asymptomatic stone. Future work should include additional well-designed randomized controlled trials with longer follow-up periods to better define when treatment should be favored over observation and patient-reported outcome measurements in addition to traditional measurements for determination of success. The overall goal should be to maximize stone removal in a single procedure without causing additional morbidity when treatment is favored and avoiding unnecessary procedures.