Imaging of COVID-19 pneumonia: a critical care perspective

Author: Dr Greg Brogan – Peer Reviewer: A/Prof Chris Nickson

OVERVIEW

COVID-19 lung imaging is generally indicated in any COVID-19 patient with worsening respiratory status

  • commonly manifests as ground glass opacities (CT chest), distributed bilaterally in bases and peripheries 
  • evolves rapidly and lung involvement is associated with severity; findings progress over 1-3 weeks, typically peaking at 10-14 days
  • findings may be present in asymptomatic individuals or pre-symptomatic individuals and may be absent early in the course of disease

In general, the lung imaging findings of COVID-19 patients are consistent with other viral pneumonias – there is no proven specific finding for COVID-19, though there may be suggestive patterns.

CHEST RADIOGRAPHY

Abnormalities are seen on chest x-ray (CXR) and are more common in severe COVID-19 disease 

Features Include (Guan, WJ et. al. 2020 Wong, HYF, et al. 2020)

  • Bilateral shadowing (72.9%) – mostly ground glass opacity (68.5%)
  • Unilateral disease (25%)
  • Local patchy shadowing
  • Interstitial abnormalities (less common finding, <5% in some studies)
  • Pleural effusions are uncommon
Chest x-ray from Canada’s first case of COVID-19
Figure 1: Chest x-ray from Canada’s first case  of COVID-19 (Silverstein, et al. 2020) : it shows bilateral peribronchovascular, ill defined opacities in all zones of the lung. 

COMPUTED TOMOGRAPHY (CT)

Abnormalities are seen on CT in a majority of COVID-19 cases (86% (Guan, WJ et. al. 2020))

Common CT features (Guan, WJ et. al. 2020 Ye, Z et al 2020 Zhao, W et al. 2020)

  • Ground Glass Opacities (GGOs)(Ye, Z et al 2020)
    • Hazy areas with increased density and no obscuring of bronchial or vascular markings (see figure 2)
    • Most common manifestation – in approximately 88% of cases (Salehi S et al. 2020)
    • Most often bilateral (87.5%), peripherally distributed (76%) and multilobar (78.8%) (Salehi S et al. 2020)
  • Reticular Pattern (Ye, Z et al 2020)
    • Multiple small linear opacities (see figure 2)
    • Common, perhaps second most common pattern to GGOs
  • Consolidation (Ye, Z et al 2020)
    • Air spaces replaced with fluid which obscures margins of vessels and airways (see figure 3)
    • Sign of progression of disease
    • Multifocal, patchy or segmental
    • Often subpleural or along bronchovascular bundles
  • Crazy Paving Pattern (Ye, Z et al 2020)
    • Resembles irregular paving stones from thickened interlobular septa/intralobular lines superimposed onto GGO (see figure 3)
    • Seen in 5-36%

Uncommon CT manifestations include (Salehi S et al. 2020, Rodriguez JCL. et al 2020)

  • Pleural effusion
  • Pericardial effusion 
  • Lymphadenopathy
  • Cavitation
  • CT Halo sign
  • Pneumothorax

Super-infection may be suggested by pleural effusion, extensive tiny lung nodules, tree-in-bud and lymphadenopathy (Rodriguez JCL. et al 2020)

When followed over time, a pattern to stages of disease emerges (Li, M et al 2020)

  • Early Phase – Moderate clinical manifestations with lesions limited to single or multiple areas
  • Progressive phase – Lesions progress in extent and density with the accumulation of cellular exudate in alveoli 
  • Severe Phase – Pulmonary lesions reach a peak at around 14 days with dense bilateral infiltration and a large amount of cellular exudate
  • Dissipative Phase – after 14 days, gradual absorption of lesions occurs (may occur earlier if disease course shorter) 

Role of CT in diagnosis: 

  • A single study of 1014 patients in Wuhan suggested high sensitivity (97%), but low specificity (25%) to detect disease the during outbreak (Ai, T et al. 2020)
  • A small study of CT-radiologists were able differentiate COVID from non-COVID viral pneumonias (Bai, HX 2020), however they had a wide range of sensitivity (67-93%) and specificity (7-100%)
  • Advantage of faster availability than PCR tests, though non-specific and risks of transport remain 
  • Changes can even be seen in asymptomatic patients (Shi, H et al. 2020)
  • However, findings are time dependent (Rodriguez JCL. et al 2020) – Approximately half may have normal study 2 days after symptoms onset. 
Shows isolated ground glass opacity in right lower lobe
Figure 2: a. isolated ground glass opacity in right lower lobe; b. subpleural consolidation (Ye, Z et al 2020)
Shows a reticular pattern in the left lower lobe
Figure 3: a. reticular pattern in the left lower lobe; b. Right middle lobe demonstrates the crazy paving pattern from reticular pattern superimposed on ground glass opacities. (Ye, Z et al 2020)

Lung Ultrasonography (US)

The role of lung ultrasonography is still being defined, but no specific COVID-19 findings have been confirmed (Soldati G et al. 2020, Vetrugno, L et al 2020)

  • Only sparse case series and case reports currently available

Uses

  • May help reduce the amount of CT scans and X-rays required (Vetrugno et al 2020) 
  • May provide a useful alternative in a climate where transport capabilities, staffing and imaging availabilities are stressed (Smith et al 2020)

Cases exhibit presence of viral pneumonia with features including (Buonsenso, D et al. 2020):

  • Irregular pleural line
  • B-lines (may be irregular and even confluent)
  • Patchy pattern with bilateral sparing
  • Areas of white lung
  • Subpleural consolidations

Risks

  • It is important to consider infection control and prevention of transmission via contact with ultrasound machine
Images from confirmed COVID-19 patient.
 Figure 5: Images from confirmed COVID-19 patient. White boxes: demonstrate pleural line irregularities; White arrows: Thick irregular B lines; White arrowheads: Subpleural consolidations; Red arrow: areas of white lung (Buonsenso, D et al. 2020)

References

LITFL

Journal articles

FOAM and web resources

SARS-CoV-2

novel coronavirus of COVID-19

Updates

Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the  Clinician Educator Incubator programme, and a CICM First Part Examiner. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.

His one great achievement is being the father of three amazing children.

On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump. | INTENSIVE | RAGE | Resuscitology | SMACC

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