Fig. 1

Computed tomography (CT) manifestations of a urachal carcinoma and a benign urachal mass. a On an axial view of a urachal carcinoma, the red arrow indicates the Retzius space without fat infiltration, and the yellow arrow indicates a lack of thickening of the surrounding bladder wall. b On an axial view of a urachal carcinoma, the red arrow indicates the Retzius space without fat infiltration, and the yellow arrow indicates calcification in central lesions. c On an axial view of a benign urachal mass, the red arrow indicates fatty infiltration of the Retzius space, characterized by enhancements of some patches or strips and vague indications of fat surrounding the lesions, and the yellow arrow indicates diffuse thickening of the bladder wall not only around the lesions but also across the whole bladder dome and two side walls, with the peripheral wall gradually thinning to normal