Agreement of Gallbladder Reporting and Data System for Gallbladder Wall Thickening at Ultrasonography: A Multireader Validation Study

Objective

This article aims to evaluate the intrareader and interreader agreement of ultrasound (US) gallbladder reporting and data system (GB-RADS) and validate the risk of malignancy in each GB-RADS category.

Materials and methods

This retrospective study comprised consecutive patients with nonacute gallbladder wall thickening who underwent US evaluation between January 2019 and December 2022. Three radiologists independently read the static US images and cine-loops for GB-RADS findings and assigned GB-RADS categories. The intraobserver (static images) and interobserver (static images and cine-loops) agreement was calculated using kappa statistics and Krippendorff's alpha. Another radiologist assigned a consensus GB-RADS category. The percentage of malignancy in each GB-RADS category was calculated.

Results

Static US images of 414 patients (median age, 56 years; 288 women, benign = 45.6% and malignant = 54.4%) and cine-loops of 50 patients were read. There was weak to moderate intrareader agreement for most GB-RADS findings and moderate intrareader agreement for the GB-RADS category for all readers. On static images, the interreader agreement was acceptable for GB-RADS categories. On cine-loops, the interreader agreement for GB-RADS findings and categories was better than static images. The percentage of malignancy was 1.2%, 37%, 71.1%, and 89.1% in GB-RADS 2, 3, 4, and 5 categories.

Conclusion

GB-RADS has moderate intrareader for GB-RADS categories. As originally proposed, the risk of malignancy is negligible in GB-RADS 2 category and highest in GB-RADS 5 category. However, the discriminatory performance of GB-RADS 3 and 4 categories is low. Larger multicenter studies with more readers must assess the reader agreement and validate the GB-RADS systems for wider clinical utilization.