Stone Impaction Risk Score: Settling the Debate or Sparking a New One?

Abstract

Objective: To develop a novel scoring system-the Stone Impaction Risk Score (SIRS)-based on non-contrast computed tomography (NCCT) parameters for preoperative prediction of impacted ureteral stones, and to compare its diagnostic accuracy with three established models: the Impacted Stone Formula (ISF), Wang nomogram, and Qi nomogram.

Methods: A total of 466 adult patients who underwent ureteroscopy for solitary ureteral stones measuring 5-10 mm between January 2019 and January 2025 were retrospectively analyzed. A total of 233 patients with impacted stones were matched 1:1 with 233 non-impacted controls. Preoperative NCCT was used to record stone dimensions, ureteral wall thickness (UWT), and Hounsfield unit (HU) measurements. The SIRS formula was defined as: (Stone width × Stone depth/(Stone length)²) × UWT × (HU below/HU above). Receiver operating characteristic (ROC) analysis and DeLong test were used to evaluate and compare model performances.

Results: The SIRS demonstrated the highest discriminative ability among all scoring systems, with an area under the curve (AUC) of 0.962 (95% CI: 0.948-0.977, P <.001), sensitivity of 88%, and specificity of 92% at the optimal cutoff value of 3.0. In comparison, the AUCs for ISF, Wang, and Qi nomograms were 0.868, 0.850, and 0.813, respectively. Pairwise DeLong tests revealed that SIRS significantly outperformed all other models, while differences among other scores were not statistically significant.

Conclusion: The SIRS outperforms three existing models within the same patient group by integrating both anatomical and local inflammatory findings, resulting in enhanced accuracy and reliability in comparative evaluations.