What are B lines?

Lung US was neglected as a diagnostic modality until it was realised that abnormal lung parenchyma was easily visualised using ultrasound. Point of care thoracic US (POCUS) is extremely useful in the Emergency Department.

Can you see the bright torch-like projections beaming from the pleural surface?

B lines have distinctive features
– hyperechoic vertical ray like projections
– run from pleural surface to the periphery
– cross & obliterate A lines
– 3 or more B lines in a single rib window are pathological
– presence of B lines excludes a pneumothorax at that site
– also known as comet tail artefacts or lung rockets

Lung interstitial disease (pneumonia, pulmonary oedema) cause subpleural interlobular septa to accumulate fluid and widen. These fluid-filled septa allow ultrasound waves to reflect several times and the artefact known as B lines are produced
Do not confuse US B lines with Kerley lines on a plain chest film
Certain B line patterns represent different lung pathologies – read more about it here
Vive PoCUS!


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