Flexible ureterorenoscopy (URS) more effectively treats kidney stones 5 to 20 mm in diameter— including stones outside the lower pole – than extracorporeal shock wave lithotripsy (ESWL), researchers have concluded.

Christian D. Fankhauser, MD, of the University of Zurich in Switzerland, and his team retrospectively studied a cohort of 1282 patients treated at their center from 2003 to 2015. Of these, 999 (78%) and 283 (22%) underwent ESWL and URS, respectively. All patients had previously untreated kidney stones and a stone diameter of 5 to 20 mm.

According to results published in Clinical Kidney Journal, URS exhibited both significantly higher stone-free (84% vs 71%) and freedom from reintervention (79% vs 55%) rates. The same trend appeared in subgroup analyses. URS was superior to ESWL for non-lower-pole stones with respect to stone-free rate (82.4% vs 68.2%) and freedom from reintervention rate (77.2% vs 52.5%).

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In multivariable regression analysis, ESWL was independently associated with a significant 58% decreased odds for being stone free and 66% decreased odds for freedom from reintervention compared with URS. Stone size also independently predicted both outcomes.

Results for lower pole stones agreed with those from a previous meta-analysis. In the current study, URS had a nonsignificant higher stone-free rate (88.9% vs 80.2%) and a significantly higher freedom from reintervention rate (91.7% vs 61.1%). The authors said freedom from reintervention more strongly reflected efficacy.

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Few complications occurred with either treatment. Clavien Grade 3a complications developed in 0.8% and 0% and Grade 3b complications in 0.5% and 0.4% of ESWL and URS patients, respectively. The most common complication was urinary tract infection, which supports the role of preprocedural urine culture, according to the authors.

“In the absence of RCTs [randomized controlled trials] for non-lower pole kidney stones, this study is the largest comparative study of treatment efficacy and safety between ESWL and URS, providing evidence that URS might be the better treatment option in untreated kidney stones up to 20mm in size,” Dr Fankhauser and his colleagues concluded.


Fankhauser CD, Hermanns T, Lieger L, et al. Extracorporeal shock wave lithotripsy versus flexible ureterorenoscopy in the treatment of untreated renal calculi. Clin Kid J. 2018;1–6. doi:10.1093/ckj/sfx151