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Lung Ultrasound: Pathology

Lung Ultrasound: Pathology
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Common LunG pathology

The following are common lung pathology that can be picked up with lung ultrasound.

  1. Pneumothorax
  2. Interstitial oedema (pulmonary oedema)
  3. Subpleural consolidation
  4. Lung consolidation
  5. Pleural effusions

Pneumothorax

Lung ultrasound findings:

  1. Absent lung sliding – indicates possible pneumothorax, but this sign can also be seen with other conditions such as apnea, emphysematous bullae or endobronchial intubation.
  2. Lung point – confirms with almost 100% certainty that a pneumothorax is present.
  3. Barcode sign on M-Mode.
The pleural line is indicated by the arrow. Note the absent lung sliding. The pleural is statis and has lost it's ants marching appearance.
The image shows a lung point. There is lung sliding on the left of the pleura and absent lung sliding on the right.

Interstitial Oedema

Interstitial oedema is typically seen on ultrasound as B-lines.

B-lines are laser like bright lines that appear to arise from the ultrasound probe and extend all the way to the bottom of the screen.

3-5 B-lines per rib space can be seen in normal lungs, but anything more than that is considered abnormal.

Image shows B-lines

Subpleural consolidation

Subpleural consolidation refers to a lung ultrasound finding where an area beneath the pleura contains a small area of fluid or consolidation.
 
Causes:
Subpleural consolidation can be caused by a variety of factors, including: 
  • Pneumonia: Inflammation of the lung tissue, often due to infection.
  • Atelectasis: Collapse of a lung lobe or segment.
  • Pulmonary Embolism: A blood clot that travels to the lungs.
  • Lung Contusion: Bruising of the lung tissue.
  • Malignant Processes: Primary or metastatic lung cancer.
  • COVID-19
  • Other respiratory viruses
  • Fibrosis
Image shows subpleural consolidation. Note the black fluid filled area just under the pleural surface.

consolidation

As even more fluid builds up in the lung, parts of the lung can become completely fluid-filled, leading to consolidation. This is commonly seen in pneumonia. Note that consolidation can also be due to atelectasis from airway obstruction (i.e. mucous plug) or extrinsic compression (i.e. large pleural effusion).

As fluid build-up progresses, your ultrasound findings will progress from multiple B-lines, confluent B-lines, subpleural consolidation, the shred sign, to a dense consolidation. Once the air is completely gone from the lung and replaced with fluid this will result in an echogenic structure on ultrasound similar to echogenicity of the liver. This is termed “hepatization of the lung.”

A consolidated lung is seen. The scan is performed at the right lung base with a curvilinear probe. The diaphragm is seen, and above the diaphragm, the pus filled collpased lung takes on the appearance of liver on ultrasound.

Pleural Effusions

Pleural effusions are seen as dark hypoechoic spaces, best appreciated at the lung bases.

When fluid is present in the pleural space, ultrasound waves travel unimpeded to the penetrate to all structures including the spine. This is called the positive spine sign and is seen in pleural effusions. 

A large pleural effusion is seen. The diaphragm and liver are to the right of the image. The black area represents fluid in the pleural space.