Detection of Ureteral Stones in Kidney Ureter Bladder Radiography: Use-fulness of Digital Post-processing

Purpose: Kidney, Ureter, and Bladder radiography (KUB) has frequently been used in suspected urolithiasis, but its performance is known to be lower than that of Computed Tomogra-phy (CT). This study aimed to investigate the diagnostic performance of digitally KUB in the detec-tion of ureteral stones. Materials and Methods: Thirty patients who underwent digital KUB and CT were included in this retrospective study. The original digital KUB underwent post-processing that involved noise esti-mation, reduction, and whitening in improving the visibility of ureteral stones. Thus, 60 digital orig-inal or post-processed KUB images were obtained and ordered randomly for blinded review. After a period, a second review was performed after unblinding stone laterality. The detection rates were evaluated at both initial and second reviews, using CT as a reference standard. The objective (size) and subjective (visibility) parameters of ureteral stones were analyzed. Fisher's exact test was used to compare the detection sensitivity between the original and post-processed KUB data set. Visibili-ty analysis was assessed with a paired t-test. The correlation of stone size between CT and digital KUB data sets was assessed with the Pearson's correlation test. Results: The detection rate was higher for most reviewers once stone laterality was provided and was non-significantly better for the post-processed KUB images (p > 0.05). There was no signifi-cant difference in stone size among CT and digital KUB data sets. In all reviews, visibility grade was higher in the post-processed KUB images, irrespective of whether stone laterality was provid-ed. Conclusion: Digital post-processing of KUB yielded higher visibility of ureteral stones and could improve stone detection, especially when stone laterality was available. Thus, digitally post -pro-cessed KUB can be an excellent modality for detecting ureteral stones and measuring their exact size.