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Jacob Avila explains the difference between A-lines and B-lines on lung ultrasound.

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Kendall A G., M.D. -

I am an old retired guy who didn't have US available when I was a young pup. Do the B lines relate to B lines on a CXR? What causes these? The big question is always WHY. If you explain WHY, they will be much easier to remember. The B lines look like pleural artifacts...perhaps like there is slight pleural fluid that is distributed with slight irregularity. The A lines look like tight reverberations or echos..perhaps between the parietal and visceral pleura. But what causes these? Thank you.

Victor U. -

The B Lines do equate to the Kerley B lines on the CXR: they are perpendicular interlobular septa, extending from the visceral pleura. They are accentuated by fluid within adjacent alveolar or interstitial tissue when these tissues undergo pathology. We all have some, but in disease states, there need to be more than 3 in more than 2 lung zones to count as pathological. Seen in pneumonia, ARDS, APO, pulmonary fibrosis, contusion.....

The A lines don't equate to the Kerley A lines on the CXR: these ones are reverberation artefact between the US probe and the plural line, as it reflects sound waves so effectively, the machine interprets multiples of the distance initially measured.

B lines obliterate A lines- you should never see the two of them together.

Hope this helps.

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