Radiological Signs of Stone Impaction Offer No Added Predictive Value for Spontaneous Passage, Study Finds

The findings indicate that RSSI does not significantly improve the accuracy of predicting spontaneous stone passage based on stone size alone. Additionally, ureteral wall thickness (UWT) measurements show moderate reliability and are subject to considerable variability between different observers.

Stone size and location are crucial for predicting spontaneous stone passage (SSP), yet the impact of radiological signs of stone impaction (RSSI) has received limited focus. The research by Marcin Popiolek, Department of Urology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden, and colleagues seeks to assess whether incorporating RSSI with stone size improves SSP predictions and to evaluate the consistency of UWT measurements across different observers.

For this purpose, the researchers analyzed data from 160 patients with a single upper or middle ureteral stone identified via acute non-enhanced computed tomography (NCCT). Patient information was gathered from medical records, and measurements of radiological signs of stone impaction —including UWT, ureteral diameters, and average attenuation above and below the stone—were conducted on NCCT scans by four independent readers who were unaware of the clinical outcomes. The study cohort was predominantly male (70%) with an average age of 51 ± 15 years.

The following were the key findings of the study:

• SSP occurred in 61% of patients over 20 weeks.
• The median stone length was 5.7 mm and was significantly shorter in patients who passed their stones at short- (4.6 versus 7.1) and long-term (4.8 versus 7.1) follow-up.
• For stone length, the area under the receiver operating characteristic curve (AUC) for predicting SSP was 0.90 and only increased to 0.91 when adding ureteral diameters and UWT.
• Ureteral attenuation did not predict SSP (AUC < 0.5).
• Interobserver variability for UWT was moderate, with ± 2.0 mm multi-reader limits of agreement (LOA).

The study faced limitations, including non-standardized follow-up and the potential for missing small, radiolucent stones on IVUs. The researchers noted that despite this, the risk of misclassification is deemed low. Multiple observers helped reduce bias, though simultaneous measurements on different reformations could introduce some subjectivity and collinearity.

In conclusion, while stone size remains a strong predictor for the spontaneous passage of upper ureteral stones, radiological signs of stone impaction do not provide additional clinically significant predictive value.

Reference:

Popiolek, M., Lidén, M., Georgouleas, P. et al. Radiological signs of stone impaction add no value in predicting spontaneous stone passage. Urolithiasis 52, 114 (2024). https://doi.org/10.1007/s00240-024-01604-0