Which ultrasound appearance best describes a simple liver cyst?

• A. Hyperechoic with irregular borders
• B. Mixed echoes with internal debris
• C. Anechoic with posterior acoustic shadowing
• D. Anechoic, well-defined border, posterior acoustic enhancement

Answer: (D)

A simple liver cyst on ultrasound is fluid-filled, so it appears anechoic with no internal echoes. The walls are thin and well defined, giving a smooth, clear border. Fluid transmits ultrasound beam well, so you see posterior acoustic enhancement—brightness behind the cyst rather than shadowing. Importantly, there are no internal septations, debris, or calcifications, and there’s typically no blood flow within the lesion on Doppler.

The other appearances don’t fit a simple cyst: a hyperechoic lesion with irregular borders suggests a solid or fibrotic process rather than a fluid-filled cavity; mixed echoes with internal debris point to a complex or infected cyst; anechoic with posterior shadowing would indicate attenuation behind the lesion, which is not characteristic of a simple cyst and suggests something denser or calcified.