Which sonographic feature is indicative of a benign liver lesion?

Anechoic appearance with smooth borders is a key feature in identifying benign liver lesions, such as simple cysts or hemangiomas. These lesions typically have a clear, fluid-filled composition, allowing them to appear anechoic (echo-free) on a sonogram. The smooth borders indicate that the lesion is well-defined and not infiltrative, which aligns with the characteristics of benign growths.

In the context of liver lesions, an anechoic appearance suggests that the lesion is homogeneous and filled with fluid, further supporting the diagnosis of benignity. This characteristic is crucial in distinguishing these lesions from malignant ones, which often present with irregular or poorly defined borders and more complex internal structures.

The other features presented in the choices, such as hypo-echoic surrounding tissue, complex internal architecture, and heterogeneous echogenicity, are typically associated with more complex lesions or malignancies, which can indicate a need for further investigation or intervention. In contrast, the anechoic appearance and smooth borders offer a more reassuring presentation and align with the benign nature of the lesion.