Figure 2.

Common signs and artefacts in LUS. (A) Normally aerated lung parenchyma. The pleural line (PL) can be recognised as a hyperechoic horizontal line, surrounded by two ribs (bat sign). A-lines are reverberation artefacts which can be visualised as equidistant motionless horizontal lines. Note lung sliding is a dynamic sign and cannot be visualised in a static picture. (B) Partially aerated lung parenchyma. Abnormal presence of fluid in the lung parenchyma is responsible for the presence of B-lines (*), which are beam-like hyperechoic vertical artefacts arising from the PL. Note B-lines always reach the edge of the image and erase A-lines. (C) Completely de-aerated lung parenchyma. Consolidation originates a tissue-like appearance of the lung (TLAL), inside which air bronchogram (AB) might be visualised as hyperechoic images. (D) Subpleural consolidation (SPC). Subpleural consolidations are defined as small (<2 cm) rounded or triangular-shaped hypoechoic areas with ill-defined hyperechoic limits, in contact with the PL.