Role of conventional ultrasonography in the diagnosis of gallbladder polypoid lesions.

The major role of conventional ultrasonography (US) can be divided into three processes: cancer screening, differential diagnosis, and assessment of the depth of tumor invasion. As US is a simple and minimally invasive modality, it is widely used for cancer screening and health checkups. Both gallbladder (GB) polyps and thickened wall of the GB are common US findings. On the contrary, US is prone to interference from gas echoes, and its diagnostic accuracy depends on both the US technology and the ability of sonographers. It is also important to be well acquainted with characteristic artifacts and how to manage their influence. Furthermore, magnified images acquired using high-resolution US (HRUS) are strongly helpful to pick up small lesions. As for differential diagnosis, classification of GB polypoid lesions (GPLs) into pedunculated or sessile (broad-based) types is very important. Cholesterol polyps in pedunculated lesions and localized adenomyomatosis (ADM) in sessile lesions are the most important targets to be differentiated. Furthermore, significant findings including number, size, growth rate, shape, internal echo, surface contour, and internal structure should be evaluated and judged as a whole. Usually, US delineates the GB wall as a two- or three-layer structure. However, as the inner hypoechoic layer includes not only the mucosa and muscularis propria but also the fibrous layer of subserosa, the differentiation between T1 (confined to the mucosa or muscularis propria) and T2 (invading the subserosa) based on the layer structure is difficult. Shape, size, and internal echo structure may be helpful for further assessment.