I see this structure in some of my patients and I am wondering if you could recognise what this represent? It is sometimes mistaken as an ablation zone if patient happens to have one at segment 8 (in the video, the RFA site is vaguely seen just anterior to the structure in question, 4 sec into the video). I looked up liver anatomy and wonder if this could be the triangular ligament?
As the ribs pass around behind the liver you often see an echogenic line protruding into the posterior edge of the liver. The diaphragm is not a smooth structure, it has to sit between the liver / lung and posterior ribs. The diaphragm, rather than being a lovely smooth echogenic line is often more irregular.
I think this is what you are seeing.
I see it often and next time I see it, I will take some axial and sagittal videos and post them here.