Objectives: Non-contrast computed tomography (NCCT) is used before retrograde intrarenal surgery (RIRS) to describe stone size, location, and complexity, but the best way to summarize stone burden remains unsettled. Therefore, we compared multidimensional NCCT-derived burden metrics with cumulative stone diameter (CSD) with respect to their ability to predict stone-free rate (SFR) and operative time after RIRS. Methods: We reviewed 352 RIRSs performed by one surgical team from April 2024 to May 2026. The primary SFR endpoint was defined as no residual fragments or a maximum residual fragment size of ≤4 mm, with 1-month computed tomography (CT) used as the reference imaging modality. Strict 0 mm CT stone-free status was analyzed as a sensitivity endpoint. The candidate predictors included one-dimensional, two-dimensional, estimated three-dimensional, spatial-distribution, attenuation, and distribution-complexity metrics extracted from preoperative NCCT. The cohort was split into training (n = 247) and validation (n = 105) sets. Results: The main model retained area-equivalent diameter, staghorn stone, and stone volume distribution entropy, with a validation area under the receiver operating characteristic curve (AUC) of 0.779. A simpler CSD model combining CSD and staghorn stone achieved a validation AUC of 0.761, without a significant AUC difference (p = 0.201). In repeated patient-level full-pipeline validation, the median validation AUC was 0.761. Under the strict 0 mm CT endpoint, the validation AUC was 0.670. Entropy showed lower selection stability in sensitivity analyses. Reclassification favored the main model (validation continuous net reclassification improvement [NRI] 0.460, p = 0.007; integrated discrimination improvement [IDI] 0.038, p = 0.003). Regarding operative time, area-, volume-, and surface-area-based metrics performed better than CSD in regard to both the whole cohort and stone-free episodes. Conclusions: NCCT-derived burden metrics can refine preoperative assessment before RIRS, but their incremental value over CSD for binary SFR prediction was modest. CSD remains a practical approximation for SFR prediction, whereas multidimensional metrics better reflect operative workload.

Objective: To identify metabolic predictors of urolithiasis recurrence and investigate whether the predictive value of urinary citrate differs across metabolic subgroups, with the aim of developing a subgroup-specific prediction model. Methods: We retrospectively analyzed patients who experienced a first episode of urolithiasis between 2013 and 2015 and subsequently underwent metabolic evaluation at the Department of Urology of our institution. Baseline assessment included demographic characteristics, blood biochemical parameters, and 24-h urinary metabolic indices. Follow-up data on stone recurrence were collected through standardized telephone interviews conducted between 2023 and 2025. Multivariable logistic regression and subgroup analyses were performed to identify predictors of recurrence. A prediction model for patients with hyperuricemia was developed using stepwise logistic regression and internally validated by tenfold cross-validation. Results: A total of 184 patients were included. Multivariable logistic regression identified 24-h urinary citrate as the only metabolic parameter independently associated with stone recurrence ( P = 0.04). Correlation analysis demonstrated significant associations between urinary citrate and serum uric acid, urinary calcium, urinary oxalate, and age. Subgroup analysis showed that the inverse association between urinary citrate and recurrence remained significant only among patients with hyperuricemia ( P = 0.03), whereas similar trends in other metabolic subgroups did not reach statistical significance. The interaction between serum uric acid and urinary citrate was not statistically significant ( P = 0.40). A preliminary prediction model incorporating urinary citrate, age, BMI, triglycerides, and parathyroid hormone demonstrated moderate discriminative performance, with a mean cross-validated AUC of 0.747. Conclusion: Urinary citrate was independently associated with urolithiasis recurrence, with this association being particularly evident among patients with hyperuricemia. These findings suggest that the predictive value of urinary citrate may vary across different metabolic backgrounds and support further investigation of metabolically stratified approaches to recurrence risk assessment. External validation in larger prospective cohorts is warranted.