Imaging in COVID

Cite this article as:
Nuala Quinn, Cian McDermott and Gabrielle Colleran. Imaging in COVID, Don't Forget the Bubbles, 2020. Available at:
https://doi.org/10.31440/DFTB.24680

The current pandemic is providing a challenge in healthcare settings whose resources are rapidly becoming strained. From the early experiences in China, it appears that children who are infected with COVID-19 have a milder course typically than that seen in adults. The radiological findings in adults include multifocal bilateral ground-glass opacities and consolidation. This is often peripheral or basal in distribution. They tend to evolve from either these bilateral ground-glass opacities on the periphery to consolidation then crazy paving. The limited initial data in children suggest that multi-lobar involvement is much less common. This is consistent with the hypothesis that children appear to have milder disease. Findings peak at 7 to 14 days and then gradually resolve. We do not yet know the radiologic sequelae.  Experience taken from the adult population in Ireland has also noted air leak complications including pneumomediastinum and pneumothorax. Pleural effusions, lymphadenopathy, and tiny lung nodules seem to be less common manifestations.

 

X-ray

The chest x-ray is, in general, the first-line imaging in children with respiratory pathology. And it is being used in COVID-19. This (pre-publication) CXR is from a case in a tertiary paediatric hospital. It shows bilateral mid-zone and left lower zone patchy consolidation and pneumomediastinum.

Ming-Yen et al describe five patients who had both chest x-rays and a CT of the thorax. Two patients showed normal CXR findings, despite having a CT examination on the same day showing ground-glass opacities. The positive CXR findings seem to appear later in the disease progression. Within the Guangdong province of the authors, a CT of the thorax is now being requested on every patient suspected of having COVID-19 regardless of risk. However, the radiation associated with CT in children does not, and cannot, support this in the paediatric setting. In sticking to the ALARA (As Low As Reasonably Achieivable) we should consider the use of another evidence-based resource – point-of-care ultrasound (POCUS).

Point of care ultrasound (POCUS) is fast becoming an established part of paediatric emergency medicine. Lung ultrasound is a mainstay of POCUS for a variety of diagnoses including pneumonia and pleural effusion. Now, there is rapidly evolving evidence on COVID-19 and POCUS lung findings.

So, how do we use ultrasound to look for ground-glass opacification and consolidation in children with suspected viral respiratory tract infection?

 

Sonographic characteristics

 

Lung US is more sensitive than CXR for interstitial patterns, small effusions, and subpleural thickening. The POCUS characteristics are similar to other causes of viral pneumonia, but in COVID-19, two studies (Huang et al and Peng et al) also described localized pleural effusions. They are more often seen with bacterial pneumonia in children, rather than viral. Large volume pleural effusions are uncommon – if you are seeing this then you need to consider other pathology.

B-lines are short-path reverberation artefacts that are found in many pathological and nonpathological states. *ISP is interstitial syndrome pattern, i.e. extensive B lines which may coalesce. This pattern is not unique to COVID-19. It is also commonly seen in pulmonary oedema. In COVID-19 these may appear in characteristic focal, multifocal and confluent patterns.

Small subpleural consolidations may be also seen. These are small hypoechoic areas inferior to the pleural line. If there is bibasal consolidation on the ultrasound, there may also be dynamic bright air bronchograms present. In COVID-19, a pleuropathy develops. This results in a thickened, irregular appearance of the pleura. There may also be skip lesions – normal pleura alongside thickened pleura with associated B-lines.

It is important to note that children may be clinically well with any of the positive lung POCUS findings.

Technique tips

The technique for POCUS lung is well described. However, for children and COVID, the following may be helpful:

  • Use the linear probe to assess pleura and look for pleural line thickening, small superficial effusions, skip lesions and B-lines.
  • Use the curvilinear or phased for lung windows. It may also be better for posterior pathology such as consolidation and air bronchograms.
  • Turn off the harmonics and spatial functioning.

And if you don’t know what any of that means then head over to Practical Pocus for a free online course and follow @Zedunow for their daily updates.

 

Decontamination and machine preparation

Infection control measures are key – the machine should go in clean and come out clean! ACEP have published an excellent COVID US cleaning protocol which is really worth a look at.

Remember to strip the machine of all non-essential items such as trays, holders and inserts and where possible avoid keyboards and use the touchscreen. Rather than multi-use bottles of gel, you should be using single-use sachets.

Handheld devices provide an alternative, with less cleaning required.

 

Photo courtesy of Cian McDermott

A word on CT

The CT findings associated with COVID-19 have been widely described: ground-glass opacities and consolidation with or without vascular enlargement, interlobular septal thickening ,and air bronchograms. Most of the studies are in affected adults and the high reported sensitivity will be affected by patient selection bias. Like the chest x-ray, it may be falsely negative in the first few days of illness. A normal CT early in disease could be falsely reassuring. Indeed, the general guidance from numerous faculties of radiology does not currently recommend CXR or CT to diagnosed COVID-19. Viral testing remains the gold standard.

 

Finally, a word on ALARA

ALARA, or making every effort to limit exposure to radiation As Low As Reasonably Achievable, is particularly relevent in COVID-19. Imaging should only be conducted for those patients where imaging will impact management of the condition. These recommendations may change as our knowledge of COVID evolves. CXR, CT and POCUS each have their own limitations, but there is emerging evidence that POCUS, in the hands of a competent practitioner, is superior in ease of access, diagnostic ability and ease of decontamination, particularly at a time when infection control is so crucial.

 

Selected references

Kanne JP, Little BP, Chung JH, Elicker BM, Ketai LH. Essentials for Radiologists on COVID-19: An Update-Radiology Scientific Expert Panel. Radiology. 2020 Feb 27:200527. https://pubs.rsna.org/doi/pdf/10.1148/radiol.2020200527.

Liu M, Song Z, Xiao K.High-Resolution Computed Tomography Manifestations of 5 Pediatric Patients With 2019 Novel Coronavirus.J Comput Assist Tomogr. 2020 Mar 25.

Ming-Yen N et al. Imaging Profile of the COVID-19 Infection: Radiologic Findings and Literature Review. Radiology 2020 Feb 13 https://doi.org/10.1148/ryct.2020200034

Huang Y et al. A Preliminary Study on the Ultrasonic Manifestations of Peripulmonary Lesions of Non-Critical Novel Coronavirus Pneumonia (COVID-19) SSRN 2020 Feb 28 https://dx.doi.org/10.2139/ssrn.3544750

Peng, Q., Wang, X. & Zhang, L. Findings of lung ultrasonography of novel corona virus pneumonia during the 2019–2020 epidemic. Intensive Care Med (2020). https://doi.org/10.1007/s00134-020-05996-6

Li Y, Xia L. Coronavirus Disease 2019 (COVID-19): Role of Chest CT in Diagnosis and Management. AJR Am J Roentgenol. 2020 Mar 4:1-7. doi:10.2214/AJR.20.22954

 

International Society Guidelines

Royal Australian and New Zealand College of Radiologists

Canadian Association of Radiologists 

American College of Radiology statement on CXR and CT findings in COVID19

Royal College of Radiology statement on CT in COVID

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About Nuala Quinn, Cian McDermott and Gabrielle Colleran

AvatarNuala Quinn is a consultant in Paediatric Emergency Medicine at Children's Health Ireland at Temple Street @Dr Quinine
Cian McDermott is a consultant in Emergency Medicine and Director Emergency Medicine Ultrasound at the Mater Hospital in Dublin @cianmcdermott
Gabrielle Colleran is a consultant paediatric radiologist at Children's Health Ireland at Temple Street @Profpayequality

Avatar
Author: Nuala Quinn, Cian McDermott and Gabrielle Colleran Nuala Quinn is a consultant in Paediatric Emergency Medicine at Children's Health Ireland at Temple Street @Dr Quinine Cian McDermott is a consultant in Emergency Medicine and Director Emergency Medicine Ultrasound at the Mater Hospital in Dublin @cianmcdermott Gabrielle Colleran is a consultant paediatric radiologist at Children's Health Ireland at Temple Street @Profpayequality

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