Stone at the same location for 2 months predicts impacted stones and stone-free status after shock wave lithotripsy for ureteral stones: A Funabashi clinic expert study.

Objectives: To evaluate the success rate of shock wave lithotripsy and identify predictors of stone-free status after shock wave lithotripsy for ureteral stones, focusing on the impact of stones remaining in the same location for 2 months (SSL2).

Methods: A retrospective analysis was conducted on 501 patients with ureteral stones treated with shock wave lithotripsy by expert surgeons (each with over 1000 shock wave lithotripsy operations) at a single Japanese institution in 2020. Logistic regression analysis identified predictors of stone-free status, including stone length, skin-to-stone distance, stone density (Hounsfield Unit), Hounsfield Unit above/below the stone, stone position, and duration of stone at the same location (SSL2).

Results: Ninety patients were excluded, resulting in 411 patients undergoing an average of 1.15 ± 0.4 sessions (range: 1-4). 344 patients (83.7%) achieved stone-free status after a single session. The overall 1-month stone-free rate was 71.4%, and the 3-month stone-free rate was 88.8%. Stone at the same location ≥2 months (SSL2) was an independent predictor of 1-month stone-free status (odds ratio = 2.25, 95%CI: 1.10-4.57, p = 0.025), while mean stone density ≥ 813 HU was an independent predictor of 3-month stone-free status (odds ratio = 2.66, 95% CI: 1.10-6.45, p = 0.03).

Conclusion: Stone at the same location ≥2 months (SSL2) was a potent predictor of 1-month and 3-month stone-free status. This condition is associated with impacted stones and can aid in decision-making for shock wave lithotripsy treatment selection.