Secondary kidney stones: to remove or not?

Pre-emptive removal of secondary* kidney stones during surgery to remove primary** stones led to fewer relapses and a similar number of emergency-department (ED) visits related to the surgery compared with leaving the secondary stones in place, a study suggests.

While some studies suggest observation or active monitoring of secondary renal stones, other data highlight the need for endoscopic surgery owing to symptomatic events within 5 years following primary stone removal (and leaving secondary stones in place). [BJU Int 2001;87:1-8; Urolithiasis 2022;50:71-77; J Urol 2009;181:1163-1168] “The debate regarding removal of asymptomatic stones has even extended to duelling editorials by experts in the field,” said the researchers.

In this study, participants underwent endoscopic removal*** of their primary and secondary stones (n=38; treatment arm) or just the primary stones (n=35; control arm). Mean follow-up was 4.2 years. [N Engl J Med 2022;387:506-513]

Compared with the control arm, the treatment arm had a lower incidence of relapse (16 percent vs 63 percent), longer time to relapse (restricted mean, 1,631.6 vs 934.2 days), and lower risk of relapse (hazard ratio, 0.18).

The number of patients having ED visits (all for stent pain) within 2 weeks following surgery was similar between the treatment and the control arms (n=5 vs 4; odds ratio [OR], 1.17), as was the number of patients who reported passing kidney stones (n=8 vs 10; OR, 0.67).

Other similarities between the treatment and control arms were the number of patients who reported asymptomatic stone or fragment passage (n=7 vs 6), time to new stone formation (restricted mean time to relapse, 1,338.8 vs 1,381.1 days), and number of patients with new stones formed (n=14 vs 13; OR, 0.99).

Removal of secondary stones however led to additional surgery time as opposed to non-removal (median, 25.6 minutes), lengthening the procedure by 38 percent (median total surgery time, 93.6 vs 59.8 minutes). “The additional 25 minutes needed to remove small, asymptomatic renal stones at the time of surgery for a primary stone … should be weighed against the potential need for repeat surgery in … patients who had a relapse,” the researchers noted.

However, in the accompanying editorial, Dr David Goldfarb from the NYU Grossman School of Medicine, New York City, New York, US, noted that the time spent to address the secondary stones following removal of the culprit stones “was nearly negligible”, considering that the procedures were performed by expert endo-urologists. [N Engl J Med 2022;387:562-563]

Not surprising, but worth conducting

“[Our findings] support removal of small, asymptomatic renal stones at the time of surgery to remove a symptomatic stone,” said the researchers. Future advances in technology and procedures that require no surgery or anaesthesia, and quality-of-life assessments may further tilt the balance in favour of early intervention, they added.

While the researchers identified the small sample size as a limitation, Goldfarb’s comment appeared to suggest otherwise. “Because there is a high likelihood that ‘silent’ stones will become symptomatic, a relatively small sample size was adequate to show a sizable benefit.”

“Although the results are not surprising, the trial was worth conducting,” continued Goldfarb. “One can imagine that elective removal may allow [patients who have had symptomatic stones] to avoid pain and trauma, inefficient and costly ED visits, infections, receipt of pain medications, and additional imaging studies.”

“An alternative to pre-emptive surgical intervention would be to finally figure out how to make those small stones detach and pass spontaneously,” Goldfarb added.