Literature
Clinical Pearls & Morning Reports
Published August 12, 2020
What are typical findings of Covid-19 pneumonia on chest CT?
Covid-19 pneumonia has a variety of appearances on chest radiography. One common appearance is bilateral hazy opacities, with or without consolidation, that predominantly involve the lower lung. Read the NEJM Case Records of the Massachusetts General Hospital Article here.
Clinical Pearls
Q: What is a common appearance of Covid-19 pneumonia on chest radiography?
A: Covid-19 pneumonia has a variety of appearances on chest radiography. One common appearance is bilateral hazy opacities, with or without consolidation, that predominantly involve the lower lung.
Q: On CT of the lungs, what is a “ground-glass opacity”?
A: Ground-glass opacity is defined as hazy opacity of the lung with preservation of bronchovascular margins. It occurs when displacement of air from the alveolar spaces increases the attenuation of the lung.
Morning Report Questions
Q: What are typical findings of Covid-19 pneumonia on chest CT?
A: Commonly reported CT findings of Covid-19 pneumonia include bilateral pulmonary opacities distributed in the peripheral lower lung. In typical cases, bilateral ground-glass opacities, sometimes with areas of consolidation, are present, and they can have an appearance suggestive of organizing pneumonia. The opacities can be multifocal, are often rounded, and can have the reversed halo sign (a focal rounded area of ground-glass opacity surrounded by a ring of consolidation). The ground-glass opacities may be peripheral and rounded but unilateral rather than bilateral, or the opacities may be peripheral but located in the upper or middle lung rather than the lower lung. In rare cases, a single ground-glass opacity with or without consolidation may be the only finding. These appearances can be confusing and mistaken for other disease processes. Findings that are atypical of Covid-19 include lobar or segmental consolidation or posterior confluent consolidation, which is more commonly seen in bacterial infection or aspiration pneumonitis; discrete small pulmonary nodules, which are sometimes seen in viral, fungal, or mycobacterial infection; and cavitation, which is suggestive of necrotizing bacterial, mycobacterial, or fungal infection. In addition, interstitial thickening and pleural effusions are atypical of Covid-19 and are suggestive of pulmonary edema.
Q: What is the role of chest CT in the management of Covid-19?
A: Guidelines from the American College of Radiology advised radiologists to avoid the use of CT for screening and as a first-line test for diagnosis; to use CT sparingly in hospitalized, symptomatic patients with specific clinical indications; and to use discretion in performing CT to inform decisions regarding whether to test, admit, or treat patients with suspected infection. The Society of Thoracic Radiology and the American Society of Emergency Radiology issued a joint position statement that advised against routine CT screening for the diagnosis of Covid-19 and proposed restricting the use of CT to patients who have tested positive for the disease and in whom complicating features such as abscess formation are suspected. The European Society of Radiology, the European Society of Thoracic Imaging, and the Fleischner Society all issued guidelines, as well. The Fleischner Society was more accepting of imaging; although the society conceded that imaging was not routinely indicated as a screening test for Covid-19 in asymptomatic patients, it endorsed the use of imaging in patients with moderate-to-severe features of Covid-19 regardless of nucleic acid test results, and it also supported the use of imaging in patients with worsening respiratory status.