Distal Acoustic shadow is seen in?
All of the above REF: Ultrasound Teaching Manual by Matthias Hofer page - 15 In simple terms when sound waves strike an interface which reflects it back, it shows on USG as a hypoechoic or anechoic shadow beyond the structure. It is seen with gas and at interface like bone, calculi and stones.
Air
Calculi
Bone
All of the above