How to interpret lung POCUS findings in patients with COVID-19

7th Jan 2021

Lung involvement is commonly seen with COVID-19 infection. In fact, there’s a typical appearance that you can see on lung ultrasound for patients with COVID-19. 

Computed tomography (CT) imaging has shown that the COVID-19 infection tends to involve the periphery of the lung. This means that clinicians can accurately scan with point-of-care ultrasound (POCUS) since the ultrasound can visualize findings that affect the pleura. 

 

Normal scan findings in lung POCUS

In a scan of a normal lung, the ribs create shadows, with A-lines below, and the pleura looks smooth and regular.

Ultrasound scan of a normal lung with labels on the pleura and A-lines.

Figure 1. In an ultrasound scan of a normal lung, the ribs create shadows, with A-lines below, and the pleura looks smooth and regular.

Check out this short video clip from our COVID Mini: Lung US Course to see an example of a normal lung scan:

 

 

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COVID-19 findings in POCUS

In patients with COVID-19, typical findings on lung POCUS include B lines, which can be scant or scattered, but can also accumulate to become confluent, and an irregular pleural line, which will often have small associated consolidations. These findings may be bilateral. It’s also common to have areas where the lung is spared and looks normal.

B-lines 

Sonographic B-lines have four key features in a lung ultrasound in patients with COVID-19: 

  1. Appear laser-like 
  2. Move with the pleura 
  3. Extend to bottom of the screen
  4. Obliterate the A-lines 

Lung ultrasound scan of patient with COVID-19 with a label on a B-line.

Figure 2. Lung ultrasound scan of a patient with COVID-19 highlighting sonographic B-lines. 

Check out this short video clip from our COVID Mini: Lung US Course to see an example of B-lines on an US from a patient with COVID-19:

 

Initially, there may not be many B-lines (Fig. 2), but, as lung involvement worsens, the number of B-lines increases and they become more dense and confluent. 

Lung ultrasound scan with labels on B-lines.

Figure 3. Lung ultrasound of a patient with COVID-19 highlighting dense and confluent B-lines.

Keep in mind, other diseases can also cause sonographic B-lines! So, it is important to look at other features of the lung ultrasound to help us decide if the B-lines are related to COVID-19 or another problem. 

As well, consider the prevalence and pre-test probability of COVID-19 for each individual patient. This means that if there is a high prevalence or pre-test probability of COVID-19 (e.g., the patient lives with others who have tested positive already), then the likelihood that the B-lines are related to COVID-19 increases. 

Irregular pleura 

The pleura of a patient with COVID-19 has two features in a lung ultrasound:

  1. Appears thick and irregular 
  2. Small consolidations visible just deep to the pleura

Lung ultrasound scan of a patient with COVID-19 highlighting the pleura and small consolidations.

Figure 4. Ultrasound scan of a lung with thick and irregular pleura and small consolidations visible just deep to the pleura. 

Check out this short video clip from our COVID Mini: Lung US Course to see an example of thick and irregular pleura and small consolidations on an US from a patient with COVID-19:

 

Areas of spared lung

Also, these effects appear to be regional in a COVID-19 patient’s lung. Areas of the lung will appear abnormal (e.g., with B-lines and small consolidations), but there will also be other areas where the pleura looks normal with no visible B-lines. This is due to the tendency of the SARS-CoV-2 virus to affect dependent and posterior lung segments first—or even adjacent rib spaces.

The overall look of the lung can be the same as acute respiratory distress syndrome or bronchiolitis in children. This highlights the need to interpret our scans in light of COVID-19 prevalence and pre-test probability.

You may also see small pleural effusions, unilateral or bilateral, in patients with COVID-19; while large pleural effusions are uncommon. If you find a pleural effusion, consider an alternative primary diagnosis or a co-existing diagnosis. 

Lung ultrasound scan highlighting a large pleural effusion.

Figure 5. Ultrasound scan of a lung with a large pleural effusion, which is not typically seen in COVID-19 patients. 

Check out this short video clip from our COVID Mini: Lung US Course to see an example of a pleural effusion on an US from a patient with COVID-19:

 

 

Relationship between COVID-19 disease severity and scan features

In general, you will find that as lung ultrasound findings accumulate (e.g., more B-lines, larger affected region, and more small consolidations), the disease severity will progress to the point where the patient will be very ill with a greater degree of hypoxia. However, there can be exceptions where the lung ultrasound may look more—or less—severe than the patient’s degree of illness. If the lung ultrasound has many B-lines but the patient is clinically doing well, then consider a period of observation before making a treatment decision.Regardless of the scan results, treat the patient in front of you! If the lung ultrasound does not show significant COVID-19 signs, then consider an alternative diagnosis to COVID-19, or come back and rescan later. Medmastery note.

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Recommended reading

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  • Long, B, Brady, WJ, Koyfman, A, et al. 2020. Cardiovascular complications in COVID-19. Am J Emerg Med38: 1504–1507. PMID: 32317203
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  • Pare, JR, Camelo, I, Mayo, KC, et al. 2020. Point-of-care lung ultrasound is more sensitive than chest radiograph for evaluation of COVID-19. West J Emerg Med21: 771–778. PMID: 32726240
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