ASSOCIATION BETWEEN METABOLIC SYNDROME AND STONE-FREE OUTCOMES FOLLOWING EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY FOR UPPER URINARY TRACT STONES: A RETROSPECTIVE STUDY

Background: Metabolic syndrome (MetS) is associated with urinary stone disease, but its relationship with treatment outcomes following extracorporeal shock wave lithotripsy (ESWL) remains incompletely understood. This study investigated the association between MetS and stone-free outcomes in patients undergoing ESWL for upper urinary tract stones. Methods: This retrospective observational study analyzed 991 patients with upper urinary tract stones, including 256 patients with MetS and 735 without MetS. The primary outcome was stone-free status, and the secondary outcome was retreatment. Logistic regression analyses were performed to examine associations between MetS and treatment outcomes. Three sequential models were constructed: an unadjusted model, a model adjusted for age and gender, and a fully adjusted model additionally incorporating stone size, stone location, and hydronephrosis. Results: The overall stone-free rate was 65.2% (646/991). Patients with MetS had a lower stone-free rate than those without MetS (60.2% vs. 66.9%; continuity-corrected chi-square P = 0.059). In the unadjusted logistic regression model, the odds ratio (OR) for stone-free status was 0.746 (95% confidence interval [CI]: 0.556–1.000; P = 0.0502). After adjustment for age, gender, stone size, stone location, and hydronephrosis, MetS was associated with lower odds of stone-free status (adjusted OR = 0.671, 95% CI: 0.484–0.930; P = 0.0166). Larger stone size was associated with lower odds of stone-free status (OR per mm = 0.816, 95% CI: 0.784–0.849; P < 0.001). Moderate hydronephrosis was also associated with lower odds of stone-free status (OR = 0.565, 95% CI: 0.381–0.837; P = 0.0045). MetS was not significantly associated with retreatment (adjusted OR = 1.108, 95% CI: 0.787–1.562; P = 0.557). Conclusions: MetS was associated with lower odds of stone-free status following ESWL after adjustment for demographic and stone-related factors, whereas no statistically significant association with retreatment was observed. These findings suggest that metabolic status may provide additional information when evaluating ESWL outcomes. Further studies incorporating stone density, skin-to-stone distance, and detailed metabolic characteristics are warranted.