Factors Associated with Spontaneous Passage of Ureteral Stones: A Prospective Clinical Study

Objective: The objective of this study was to investigate factors associated with spontaneous passage (SP) of ureteral stones. Methods: The present prospective study included 113 patients with ureteral stones <1 cm, categorized into SP (n = 60) and non-spontaneous passage (NSP; n = 53) groups. Clinical, laboratory, imaging, and stone-related factors were compared between groups. Multivariable logistic regression was used to assess independent factors associated with spontaneous stone passage. Results: The median stone size (5.5 mm [interquartile range [IQR] 3.1] vs 7 mm [IQR 3.0]; P = .001) and stone burden (20.5 mm2 [IQR 29.25] vs 36 mm2 [IQR 24.25]; P = .01) were significantly lower in the SP group. The mean Hounsfield unit (HU) of the stones was 738 ± 38 HU in the SP group and 884 ± 37 HU in the NSP group (P = .007). Fifty-six patients (93.3%) had soft stones in the SP group, and 36 (67.9%) patients had soft stones in the NSP group (P = 0.001). A lower C-reactive protein (CRP) level was statistically associated with SP (26.7% vs 50.9%; P = .007). Hematuria was also associated with SP (80% vs 62.3%; P = .041). In multivariable analysis, stone size remained independently associated with SP (adjusted odds ratio: 0.63 per 1-mm increase; 95% confidence interval: 0.45-0.88; P = .007). Conclusion: Stone composition was not associated with ureteral spontaneous stone passage. Although stone size remained independently associated with SP after adjustment for other relevant variables, stone burden, HU and hardness of the stone, hematuria, and serum CRP level were associated with spontaneous stone passage in univariable analysis. These parameters should be considered when selecting patients for active surveillance of SP. Cite this article as: Karadayı M, Oğuz U, Öğreden E, et al. Factors associated with spontaneous passage of ureteral stones: A prospective clinical study. Urol Res Pract. 2026;52, doi:10.5152/tud.2026.26023