Chest CT features of coronavirus disease 2019 (COVID-19) pneumonia: key points for radiologists

Abstract

COVID-19 is an emerging infection caused by a novel coronavirus that is moving so rapidly that on 30 January 2020 the World Health Organization declared the outbreak a Public Health Emergency of International Concern and on 11 March 2020 as a pandemic. An early diagnosis of COVID-19 is crucial for disease treatment and control of the disease spread. Real-time reverse-transcription polymerase chain reaction (RT-PCR) demonstrated a low sensibility; therefore chest computed tomography (CT) plays a pivotal role not only in the early detection and diagnosis, especially for false negative RT-PCR tests, but also in monitoring the clinical course and in evaluating the disease severity. This paper reports the CT findings with some hints on the temporal changes over the course of the disease: the CT hallmarks of COVID-19 are bilateral distribution of ground glass opacities with or without consolidation in the posterior and peripheral lung, but the predominant findings in later phases include consolidations, linear opacities, "crazy-paving" pattern, "reversed halo" sign and vascular enlargement. The CT findings of COVID-19 overlap with the CT findings of other diseases, in particular the viral pneumonia including influenza viruses, parainfluenza virus, adenovirus, respiratory syncytial virus, rhinovirus, human metapneumovirus, etc. There are differences as well as similarities in the CT features of COVID-19 compared with those of the severe acute respiratory syndrome. The aim of this article is to review the typical and atypical CT findings in COVID-19 patients in order to help radiologists and clinicians to become more familiar with the disease.

Keywords: Chest CT; Consolidation; Coronavirus pneumonia; Crazy-paving pattern; Ground glass opacities; Lungs; Reticular pattern.

Fig. 1

Average percentage of each chest CT manifestation of COVID-19 calculated from published studies

Fig. 2

64-year-old man with COVID-19 in early stage of illness. Chest CT scan showing bilateral GGOs in the apical segments of both lower lobes (white arrows)

Fig. 3

77-year-old man with COVID-19 in intermediate stage of illness. Chest CT scan showing large bilateral areas of consolidation with an air bronchogram in both lower lobes (black arrows). Less extensive consolidations can be seen in the left upper and middle lobe (white arrowheads), as well as a solid nodule surrounded by a ground glass halo in the middle lobe (white arrow)

Fig. 4

69-year-old woman with COVID-19 in remission stage of illness. Chest CT scan showing GGOs and thickened pulmonary interstitial structures (black circles), with a reticular pattern and fibrous stripes in both lower lobes (black arrows)

Fig. 5

67-year-old man with COVID-19 in intermediate stage of illness. CT scan showing bilateral multifocal GGOs with superimposed interlobular septal thickening and visible intralobular lines (“crazy-paving”) (black circles). Bronchial wall thickening (black arrowhead) and multiple small vascular enlargements (“white arrowheads”) can also be seen in the right upper lobe

Fig. 6

70-year-old woman with COVID-19 in intermediate stage of illness. CT scan showing the presence of right pleural effusion (white full arrow), and consolidation and pleural thickening in the left lower lobe (white empty arrow)

Fig. 7

59-year-old woman with COVID-19 in intermediate stage of illness. CT scan showing a reversed halo sign (focal rounded GGOs surrounded by ring-like consolidation) in the anterior segment of the right upper lobe (white circle). It also shows GGOs bilaterally in the upper lobes and in the apical segment of the left lower lobe, with superimposed interlobular septal thickening and intralobular lines (“crazy-paving”) in the left lung (white full arrowheads), and focal consolidation with an air bronchogram in the right upper lobe (white empty arrowhead)

Fig. 8

80-year-old man with COVID-19 in worsening stage of illness. Chest CT scan showing enlarged mediastinal lymph nodes (white arrows)

Fig. 9

75-year-old man with COVID-19 in worsening stage of illness. CT scan showing pericardial effusion (white full arrow) and multiple extensive consolidations in both lower lobes and in the left upper lobe (white empty arrows)

Fig. 10

67-year-old man with COVID-19 complicated by pulmonary embolism, in worsening stage of illness. CT Angiography. Image shows a pulmonary embolus in a segmental branch of the right pulmonary artery for the middle lobe (white arrow) in a patient with bilateral consolidations and pleural effusion (empty arrows)