Question 30.3

List the ultrasound features of a pneumothorax.

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College Answer

  • Loss of comet tails and “marching ants” appearance
  • Ribs and pleura move together
  • “Lung point” – motionless horizontal lines are replaced by normal lung appearance moving from non-dependent to dependent region and also seen with inspiration and the probe held stationary.
  • Loss of “waves on the beach” appearance in M-mode


This is one of those things which is better explained with pictures.

In dry boring words, there is a list of features which one can easily memorise:

  1. Absence of "Seashore sign" on M-mode
  2. Absence of "B-lines" or "comet-tails" moving in synchrony with the pleura
  3. Absence of sliding lung
  4. Lung point sign - the point where the pneumothorax transitions into normal lung


Husain, Lubna F., et al. "Sonographic diagnosis of pneumothorax." Journal of Emergencies, Trauma & Shock 5.1 (2012).