Which ultrasound finding is characteristic of gallstones?

• A. Anechoic gallbladder
• B. Echogenic foci with posterior acoustic shadowing
• C. Hypoechoic liver
• D. Increased vascularity of gallbladder wall

Answer: (B)

Gallstones appear on ultrasound as bright echoes within the gallbladder that cast posterior acoustic shadowing. Their dense, calcified nature reflects most of the ultrasound waves, so you see a highly echogenic focus and a dark shadow behind it. This shadowing behind a bright focal point is the defining sign of stones, helping distinguish them from other brightenings. Stones can be mobile with changes in position and often settle in the dependent portion of the gallbladder. In contrast, an anechoic gallbladder suggests clear bile without stones, a hypoechoic liver is unrelated to stones, and increased vascularity of the gallbladder wall points to inflammation such as cholecystitis rather than the stones themselves.