Ultrasound Level 1 Tutorial: Lung Ultrasound
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Tutorial: Lung Ultrasound
Learn ultrasound of the lung. Identify pneumothorax, pleural effusions and wet lungs.
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Tutorial: Lung Ultrasound Pleural Effusion
Times Practiced
Cases Completed
1h 24m
Total Time spent
1m 24s
Average Time
Pleural Effusion
Pleural Effusions
Normally there are 2-10 ml of fluid in pleural space.

In pathological conditions causing pleural effusions, the volume of fluid is increased. We can identify this fluid with non-invasive imaging:
  • upright CXR - 100 -150 ml is required to blunt the costophrenic angle 
  • supine CXR - 200 - 300 ml is required to be identified
  • ultrasound - as little as 20 ml of fluid can be identified
Probe Selection:  a low frequency probe (2-5 Mz.) for deeper penetration is best.
  • a smaller footprint is easier to get between ribs
  • the phased array ("cardiac" probe) or the curved array ("abdominal" probe) are good choices
  • do not use the linear array ("vascular" probe) - the images are too shallow
Phased array is good:

Curved array is good:

Linear array is not good:
linear array probe

Patient position
  • the patient can be either supine, semi-sitting or totally sitting up
  • raise the arm to increase space between the ribs

Step 1 – Palpate the xiphoid
  • place the probe with marker toward head on the posterior axillary line at the level of the xiphoid
      probe placement for lung ultrasound         probe placement for lung ultrasound

Step 2 – Locate the diaphragm
  • the diaphragm is a skinny, curved and bright white (hyperechoic)
  • if you are on the patient's right, you will see the liver below the diaphragm
  • if you are on the patient's left, you will see the spleen below the diaphragm
    diaphragm seen on ultrasound

Step 3 – Center the diaphragm
  • slide the probe toward (cephalad) or away from (caudad) the head to bring diaphragm into the center

Step 4 – Identify the pleural cavity
  • remember that the orientation marker on the screen is on the left
  • the marker on the probe is toward the head
  • therefore, "screen left" = toward the head (cephalad)
  • the pleural cavity is cephalad to the diaphragm
  • therefore, the pleural cavity is to the left of the diagphragm on the screen
pleural space on ultrasound

Step 5 – Sweep anterior and posterior to view
  • identify the region where the effusion is largest
  • select this space for inserting a needle or tube, if indicated

Normal Lung findings
  • the lung is normally filled with air
  • air in lung scatters the ultrasound beam and therefore produces a snowstorm appearance

  • fluid does not reflect ultrasound waves. Therefore, fluid is anechoic = black.  
  • pleural effusions are black
  • frequently you will see atalectatic (collapsed) lung within the effusion. Lung without air takes on the appearance of a solid organ and will be white.
  • collapsed lung is white
pleural effusion on ultrasound

 if the lung is separated from the chest wall or diaphragm by more than 3 cm. of effusion, the pleural space contains at least 500 ml of fluid
pleural effusion on ultrasound

The Spine Sign

Since the beam passes though the liver to the midline, it will often encounter a series of white lines representing the spine. Bone reflects all sound back to the probe, so deep to the white line will be shadowing. 
  • since air does not transmit sound, you will not be able to see the spine above the diaphragm
  • if there is pleural effusion, then there will be no air superior to the diaphragm as the lung is displaced by fluid
  • in this situation, the sound waves will be able to travel all the way to the midline, revealing the spine
  • if you can see the spine on the left of the liver/diaphragm, this finding supports the presence of a pleural effusion

Here is example of a normal ABSENT spine sign (no effusion):
spine sign on ultrasound     spine sign on ultrasound

Here is an example of a PRESENT spine sign with pleural effusion:
spine sign on ultrasound     spine sign on ultrasound

 Here is a video showing a small effusion and the spine sign:

Loculated Effusions:
loculated effusion on ultrasound

Loculated complex effusion have a variety of appearances. Clotted blood and empyemas may take on the ultrasound characteristics of a solid organ.

  1. The pleural space is to the left of the diaphragm if screen marker on left and probe marker toward head
  2. Liquid effusions are black
  3. Effusions > 3 cm suggest effusion is > 500 ml
  4. Collapsed lung (atalectasis) is white
  5. Spine sign occurs with effusions
  6. Loculated effusions will have white stranding
  7. Clotted effusions or empyema can mimic a solid organ