B-line (ultrasound)

Dr Francis Fortin and David Carroll et al.

The B-line is an artifact relevant in lung ultrasonography. As originally described, it has seven defining features 1:

  • a hydroaeric comet-tail artifact
  • arising from the pleural line
  • hyperechoic
  • well-defined
  • extending indefinitely
  • erasing A-lines 
  • moving in concert with lung sliding, if lung sliding is present

B-line distribution corresponds with sub-pleural thickened interlobular septa, as demonstrated by CT, and are absent under normal conditions and present in alveolar-interstitial syndromes 2. Subpleural septal edema is postulated to provide a bubble-tetrahedron interface, generating a series of very closely spaced reverberations at a distance below the resolution of ultrasound which is interpreted as a confluent vertical echo which does not fade with increasing depth 3.

A few B-lines (less than 3/field of view) can often be found under normal circumstances, especially in the elderly, and around the base of the lungs 4.

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Article information

rID: 64319
System: Chest
Section: Signs
Tag: pocus, lung
Synonyms or Alternate Spellings:

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Cases and figures

  • Case 1: B-lines
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