Two in one: Overlapping CT findings of COVID-19 and underlying lung diseases

Abstract

Coronavirus disease 2019 (COVID-19) is associated with pneumonia and has various pulmonary manifestations on computed tomography (CT). Although COVID-19 pneumonia is usually seen as bilateral predominantly peripheral ground-glass opacities with or without consolidation, it can present with atypical radiological findings and resemble the imaging findings of other lung diseases. Diagnosis of COVID-19 pneumonia is much more challenging for both clinicians and radiologists in the presence of pre-existing lung disease. The imaging features of COVID-19 and underlying lung disease can overlap and obscure the findings of each other. Knowledge of the radiological findings of both diseases and possible complications, correct diagnosis, and multidisciplinary consensus play key roles in the appropriate management of diseases. In this pictorial review, the chest CT findings are presented of patients with underlying lung diseases and overlapping COVID-19 pneumonia and the various reasons for radiological lung abnormalities in these patients are discussed.

Keywords: COVID-19 pneumonia; Computed tomography; Lung diseases.

Fig. 1

COVID-19 pneumonia and ILD. Axial (a, b) and coronal (c) CT images showing bilateral round ground-glass opacities in a patient with COVID-19 pneumonia and ILD. Findings of UIP, such as peripheral and basal ground-glass opacities, traction bronchiectasis, and honeycombing can also be seen.

Fig. 2

COVID-19 pneumonia and connective tissue diseases. Axial CT image (a) of a patient with systemic sclerosis shows lung involvement findings such as peripheral opacities, reticulations, and traction bronchiectases. There are also bilateral GGOs in the lower lobes due to COVID-19 pneumonia (a, white arrows).The GGOs regressed in the follow-up CT image (b) obtained 3 months later. Esophageal dilatation due to scleroderma involvement can be seen on both CTs (a, b, red arrows). Axial CT image (c) of a patient with RA and COVID-19 pneumonia showing bilateral cavitating rheumatoid nodules, and peripheral GGOs in the left upper lobe due to COVID-19 pneumonia. Cavitary rheumatoid lung nodules and cavitary superinfections may mimic each other in COVID-19 pneumonia. Axial CT image (d) of another patient with COVID-19 pneumonia and without CTDs, showing cavitary opacities in the right lower lobe and lingula (arrows). Deep tracheal aspiration and blood culture revealed Acinetobacter baumanii superinfection.

Fig. 3

COVID-19 pneumonia and GPA. Axial CT image of a patient with known GPA (a) shows GGOs with superimposed septal thickenings in the upper lobe compatible with COVID-19 pneumonia. Axial CT image (b) demonstrates circumferential tracheal wall thickening (arrow) due to GPA involvement. Tracheal stenosis can also be seen in COVID-19 pneumonia due to prolonged intubation. Axial (c) and coronal (d) CT images of another patient show post-intubation tracheal wall thickening and stenosis (arrows).

Fig. 4

COVID-19 pneumonia and asbestosis. Axial CT images (a, b) demonstrate bilateral calcified pleural plaques secondary to asbestosis and bilateral GGOs due to COVID-19 pneumonia. In the previous CT image (c) (8 months earlier) there are reticular densities and mild GGOs adjacent to the pleural plaques compatible with asbestosis, which may be confused with COVID-19 pneumonia.

Fig. 5

COVID-19 pneumonia and cystic fibrosis. Axial (a) and coronal (b) CT images show widespread bronchiectases and bronchial wall thickenings in both lungs due to cystic fibrosis. In the left lung, multiple cystic bronchiectases have destroyed the lung parenchyma causing significant volume loss. GGOs can be seen in the right lung due to COVID-19 pneumonia.

Fig. 6

COVID-19 pneumonia and emphysema. Axial CT images in the upper row show lung parenchymal changes in a patient with COVID-19 pneumonia. Bilateral opacities that are seen on the first CT image (a) progressed over time to ARDS, and bilateral subpleural bullae are seen in the anterior part of upper lobes in follow-up CT image (b). The last CT image (c) shows that the opacities have regressed, but there are persisting subpleural bullae leading to pneumothorax on the left. Axial CT image of another patient (d) shows opacities due to COVID-19 pneumonia in the right upper lobe superimposed on emphysematous parenchyma. The previous CT image (e) of the same patient better delineates the emphysematous parenchyma.

Fig. 7

COVID-19 pneumonia and malignancy. Axial CT image in the mediastinal window (a) shows irregular mediastinal and costal pleural thickenings (arrows) on the left in a patient with malignant mesothelioma and COVID-19 pneumonia. Axial CT image in the lung window (b) of the same patient shows GGOs with superimposed septal thickenings in the right lung due to COVID-19 pneumonia. Axial CT images (c, d) of another patient with metastatic breast carcinoma and COVID-19 pneumonia demonstrate both round GGOs due to COVID-19 pneumonia and metastatic nodules (arrows) in both lungs.

Fig. 8

COVID-19 pneumonia and pulmonary edema. Axial CT image (a) of a patient with subacute COVID-19 pneumonia shows cardiomegaly and bilateral pleural effusions (arrow). CT image in lung window (b) demonstrates bilateral peripheral opacities due to COVID-19 pneumonia. Coronal CT image (c) shows that there are also perihilar opacities due to accompanying pulmonary edema.

Fig. 9

COVID-19 and pulmonary thromboembolism. Coronal CT image of a patient with previously diagnosed CTEPH shows chronic PTE in the right interlobar artery (arrow). Right ventricular dilatation and interventricular septal flattening due to increased right ventricular pressure is seen on axial CT image (b). Axial CT image (c) of the same patient shows bilateral peripheral GGOs compatible with COVID-19 pneumonia. Axial CT image (d) of another patient with COVID-19 pneumonia demonstrates thrombi in the right lower pulmonary artery branches (arrow). The CT image in the lung window (e) shows bilateral peripheral opacities of subacute COVID-19 pneumonia, and pleura-based opacity is seen in right lower lobe representing pulmonary infarction.