The predictive value of ureteral wall thickness for impacted ureteral stones

Objective To determine the predictive parameters of impacted ureteral stones and evaluate the predictive value of ureteral wall thickness for impacted ureteral stones. Methods A total of 93 patients with proximal ureteral stones from January 2017 to December 2017 were included in the study [71 males and 22 females, aged 30-80 years, and body mass index (23.7±2.7)kg/m2 ]. Both clinical and computed tomography urography (CTU) data were compared between patients with or without impacted ureteral stone, including sex, age, body mass index, renal pelvic diameter, longitudinal size of stone, transverse size of stone, stone surface area, stone volume, hounsfield units of stone, diameter of the ureter proximal to the stone, and ureteral wall thickness at the impacted ureteral stone site. The receiver operating characteristic curve (ROC) was used to analyze the performance of each of the above-mentioned parameters for predicting the impacted ureteral stones. Multivariate logistic regression analysis was used to select the independent risk factors of impacted ureteral stones. Results Among 93 patients, 38 (40.8%) patients were with impacted stones and 55(59.1%) without impacted stones. Univariate analysis showed significant difference in ureteral wall thickness (t=6.344, P<0.001), diameter of the ureter proximal to the stone(U=607.5, P=0.001), longitudinal size of stone(U=580.5, P<0.001), transverse size of stone(t=4.172, P<0.001), stone surface area(U=508.5, P<0.001), stone volume(U=508.5, P<0.001) and hounsfield units of stone(t=6.344, P=0.006) between patients with or without impacted stones. Ureteral wall thickness(UWT) showed the largest area under curve(AUC) among those parameters(AUC=0.825, P<0.001), followed by stone surface area and stone volume. The optimal cut-off value of ureteral wall thickness was 3.16 mm, with sensitivity of 71.1% and specificity of 85.5%. Multivariate analysis showed that ureteral wall thickness (Wald=18.709, P<0.001) and stone volume(Wald=8.391, P=0.004) were independent predictors of impacted stones. Conclusion Ureteral wall thickness was related to the presence of impacted ureteral stones and could be used for predicting impacted ureteral stones. Key words: Impacted; Ureteral stone; Prediction; Ureteral wall thickness