Prospective evaluation of ultrasound shear-wave elastography for predicting outcomes of extracorporeal shock-wave lithotripsy in proximal ureteral stones.

PURPOSE: Predicting extracorporeal shock-wave lithotripsy (ESWL) success is central to ureteral stone management. This prospective study evaluated shear-wave elastography (SWE) in 10-20 mm proximal ureteral calculi.

METHODS

Ninety patients with a 10-20 mm proximal ureteral stone were enrolled. Before ESWL, each underwent non-contrast computed tomography for Hounsfield unit (HU) quantification and ultrasound SWE. A stone-free result (residual fragments ≤4 mm) at 4 weeks defined success.

RESULTS

A stone-free result occurred in 62.2% (56/90). Stone-free patients had lower stiffness (14.6±6.1 vs. 27.6±9.1 kPa) and HU values (786±194 vs. 1,137±195 HU, both p < 0.0001). ROC-derived cut-offs were 21.2 kPa (AUC 0.871) and 935 HU (AUC 0.890). Against a zero-fragment endpoint, SWE discrimination fell (AUC 0.64). On Firth-corrected modelling, lower body mass index (p = 0.043), SWE below 21.2 kPa (p = 0.033) and HU below 935 (p = 0.004) independently predicted success. For SWE, this held only at the dichotomised cut-off; the continuous association did not reach significance (OR = 0.904 per kPa, p = 0.055). Within-session repeatability was moderate-to-good (ICC = 0.74). Adding SWE to an HU-only model did not improve discrimination (AUC 0.890 to 0.898; DeLong p = 0.585), although the likelihood-ratio test (p = 0.025) and integrated discrimination improvement (+ 0.055, p = 0.019) were significant. SWE correlated strongly with HU (ρ = 0.76, p < 0.0001).

CONCLUSION

Lower stone stiffness, dichotomised at a cohort-derived threshold, was independently associated with a stone-free outcome. SWE largely overlapped with HU and did not improve discrimination; it may therefore provide similar information by a radiation-free route where repeat CT is undesirable, rather than adding to CT. The 21.2 kPa threshold should be regarded as exploratory pending multicentre validation.