Stone Size Matters: Volume Versus Diameter in Predicting Spontaneous Passage of Ureteral Stones < 10mm

Introduction - International guidelines use maximum diameter to predict spontaneous passage of ureteral stones < 10 mm. This study compares its performance with calculated volume, a potentially more informative three-dimensional parameter. Materials and methods - Monocentric retrospective study including 121 patients admitted for renal colic. Maximum diameter and volume (calculated by ellipsoid formula and 3D segmentation) were evaluated against spontaneous passage at 4-6 weeks. Diagnostic performance of morphological parameters was evaluated by receiver operating characteristic (ROC) analysis. Multivariable logistic regression was used to identify factors independently associated with spontaneous passage. Results - Maximum diameter (AUC 0.82; optimal threshold 5.35 mm) proved significantly superior to volume for predicting spontaneous passage, with an overall passage rate of 77.7% in the cohort. In multivariate analysis, diameter ≤5.35 mm (OR = 6.84) and distal location (OR = 3.12) were the only independent predictive factors. Volumetric parameters provided no significant improvement. Conclusion - Maximum diameter remains the best predictor of spontaneous passage for ureteral stones <10 mm. Systematic integration of volume measurement in routine clinical practice appears unjustified.