Which of the following is not echogenic on ultrasonography-: (A) Bile, (B) Gas, (C) Bone, (D) Gall Stones
Answer is A. Echoes are not produced if there is no difference in a tissue or between tissues. Homogenous fluids like blood, bile, urine, contents of simple cysts, ascites and pleural effusion are seen as echo-free structures. Ref : Physical principles of ultrasound (Dr Daniel J Bell and Ass. Pr. Mirjan M. Nadrljanski et al.)