Efficacy of ultrasound monitoring during extracorporeal shock wave lithotripsy: A multi-institutional propensity score-matched study.

Objectives: To evaluate the efficacy of ultrasound-assisted monitoring during shock wave lithotripsy for kidney and proximal ureteral calculi.

Methods: We retrospectively reviewed 535 patients who initially underwent shock wave lithotripsy for renal or proximal ureteral calculi between January 2012 and December 2021. The patients were divided into the X-ray group (n = 294) and ultrasound plus X-ray group (n = 241) based on the methods of targeting and monitoring calculi during shock wave lithotripsy. Because of differences in patient backgrounds, 1:1 propensity score-based matching was performed. The primary endpoint was the stone-free rate.

Results: In the final 1:1 matched cohort, 192 kidney stone cases and 162 proximal ureteral stone cases were analyzed. For patients with kidney calculi, the stone-free rate of the ultrasound plus X-ray group was significantly higher than that of the X-ray group (66.7% vs. 47.9%; P = 0.013). In the multivariate analysis, a large stone area (odds ratio 2.37), lower caliceal stones (odds ratio 3.37), and X-ray monitoring alone (odds ratio 0.49) were independently associated with shock wave lithotripsy failure. For patients with proximal ureteral stones, there was no significant difference in the stone-free rate between the ultrasound plus X-ray group and X-ray group (71.6% and 58.0%, respectively; P = 0.100). During the multivariate analysis, high computed tomography attenuation (odds ratio 2.31) and large stone area (odds ratio 2.18) were independent factors associated with residual stones after shock wave lithotripsy.

Conclusions: Ultrasound-assisted monitoring may contribute to a higher stone-free rate for patients with kidney calculi, but not for those with proximal ureteral calculi.