A study analyzing stone-free rates after ureteroscopy suggests that urologists might consider applying refined patient selection criteria in order to achieve better outcomes.
The research, presented at the 2017 AUA annual meeting in Boston by urologists from UT Southwestern Medical Center, Dallas, found that even with aggressive manual fragment retrieval involving more than 160 passes, only 50% of patients achieved stone-free status as determined by non-contrast computed tomography (CT) scan performed 8 weeks postoperatively. Even after excluding residual fragments that were ≤2 mm, the stone-free rate was only 70%, reported first author Noah Canvasser, MD.
Results of a multivariate analysis showed that having fewer stones and ureter-only location were the only independent predictors of stone-free status.
“With both basketing and dusting techniques, it seems that ureteroscopy is being increasingly used to treat patients with larger stone burdens,” Dr. Canvasser said.
“Consistent with previous reports, our study showed that stone-free rates after ureteroscopy are disappointingly low, and therefore, intervention with percutaneous nephrolithotomy (PCNL) is still warranted for those larger stone burdens,” he added.
Dr. Canvasser conducted the study as an endourology fellow at UT Southwestern. He is now assistant professor of urology, UC Davis Medical Center, Sacramento, CA. He worked on the research with Margaret S. Pearle, MD, and colleagues.
In planning the study, Dr. Canvasser and colleagues recognized that while earlier retrospective and prospective studies that evaluated stone-free rates used stringent CT criteria, they did not consistently quantify the aggressiveness of fragment extraction.
“When performing ureteroscopy, we attempt to extract all fragments, regardless of size, and so we analyzed the number of ureteroscope passes to determine if being extremely aggressive improved the stone-free rate compared with previous reports,” Dr. Canvasser said.
The study included prospectively collected data from 132 patients (169 renal units) who underwent ureteroscopy with laser lithotripsy from December 2015 to February 2017. A ureteral access sheath was used in all cases except for those with distal ureteral stones.
The median number of stones per renal unit was two and median aggregate stone size was 13 mm. After a mean surgical time of 91 minutes and a median of 33.5 ureteroscope passes (range, 1 to 164), the stone-free rate was only 52%.
Mean number of residual fragments per renal unit was 2.1, and the median size of the residual fragments was 3 mm.
Best outcomes in stones ≤10 mm
Analyses of stone-free rates for different clinical scenarios showed the best outcome was achieved in cases of ureteral stones ≤10 mm, for which the stone-free rate was 88%. Regardless of the number of stones, about two-thirds of cases with renal stones ≤10 mm achieved stone-free status.
However, the stone-free rates in cases involving larger renal stones (11 mm to 20 mm) were especially poor—33% in cases with a solitary large stone and 30% for cases with one or more large stones.
Univariate analysis results showed stone-free status was associated with having fewer stones, a solitary stone, smaller aggregate stone size, smaller proportion of renal or renal and ureteral stones, and pre-stenting.