Imaging findings in COVID-19 pneumonia

Abstract

The coronavirus disease (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), emerged in Wuhan city and was declared a pandemic in March 2020. Although the virus is not restricted to the lung parenchyma, the use of chest imaging in COVID-19 can be especially useful for patients with moderate to severe symptoms or comorbidities. This article aimed to demonstrate the chest imaging findings of COVID-19 on different modalities: chest radiography, computed tomography, and ultrasonography. In addition, it intended to review recommendations on imaging assessment of COVID-19 and to discuss the use of a structured chest computed tomography report. Chest radiography, despite being a low-cost and easily available method, has low sensitivity for screening patients. It can be useful in monitoring hospitalized patients, especially for the evaluation of complications such as pneumothorax and pleural effusion. Chest computed tomography, despite being highly sensitive, has a low specificity, and hence cannot replace the reference diagnostic test (reverse transcription polymerase chain reaction). To facilitate the confection and reduce the variability of radiological reports, some standardizations with structured reports have been proposed. Among the available classifications, it is possible to divide the radiological findings into typical, indeterminate, atypical, and negative findings. The structured report can also contain an estimate of the extent of lung involvement (e.g., more or less than 50% of the lung parenchyma). Pulmonary ultrasonography can also be an auxiliary method, especially for monitoring hospitalized patients in intensive care units, where transfer to a tomography scanner is difficult.

Figure 1. Recommendations for performing imaging in patients with COVID-19 pneumonia. Adapted from Rubin et al (9). * Age >65 years, cardiovascular diseases, hypertension, chronic respiratory diseases, diabetes, and immunosuppression.

Figure 2. Chest radiography (A), posteroanterior view, shows retrocardiac and right peri diaphragmatic opacities (arrow), regions which are often neglected in the radiographic evaluation; there are no other notable parenchymal changes. Coronal (B) and axial (C and D) CT images on the same day show ground glass opacities associated with some consolidations in the posterior regions of both lungs, most prominent in the lower lobes. Note the slight thickening of the inter and intralobular septa that constitute the crazy-paving pattern in the right lung base (arrowhead).

Figure 3. Chest radiographs, posteroanterior views (A and B) and in bed (C), performed at intervals of 2 days, show progression of the diffuse and bilateral pulmonary opacities. Note the tracheal cannula and other vital devices (C).

Figure 4. Recommendations for categorizing computed tomography findings of COVID-19 pneumonia. Adapted from Simpson et al (8).

Figure 5. Typical findings of COVID-19. Axial CT images show peripheral, bilateral GGOs with areas of consolidation. Note the associated septal thickening.

Figure 6. Typical findings of COVID-19. Axial CT images show multifocal GGOs of rounded morphology with areas of consolidation.

Figure 7. Typical findings of COVID-19. Axial CT image shows GGO areas surrounded by rings of consolidation (reversed halo sign), complete and incomplete.

Figure 8. Indeterminate findings of COVID-19. Axial CT image shows bilateral diffused GGOs associated with consolidations, and some areas of septal thickening.

Figure 9. Indeterminate findings of COVID-19. Axial (A) and sagittal (B) CT images show unilateral GGOs in the upper segment of the left lower lobe.

Figure 10. Indeterminate findings of COVID-19. Axial CT image shows a very small GGO with a non-rounded and non-peripheral distribution.

Figure 11. Atypical findings of COVID-19. Axial CT images show (A) isolated segmental consolidation; (B) discrete small centrilobular nodules, some of them with the “tree-in-bud” pattern; (C) lung cavitations; and (D) bilateral smooth interlobular septal thickening with pleural effusion.

Figure 12. Transducer sites for lung ultrasound. The six sites are anatomically divided by the parasternal line (green line), anterior axillary line (pink line), posterior axillary line (yellow line), and paravertebral line. The subdivision in the superior and inferior takes into account the well-established Bedside Lung Ultrasound in Emergency (BLUE) protocol.

Figure 13. Lung ultrasound. Linear (A and B) and convex (C and D) transducers in intercostal spaces show irregular and thickened pleural line (white arrowhead); hypoechogenic image with irregular contours, compatible with subpleural consolidation (black arrowhead); multifocal B-lines (white arrow), some of which are coalescent (black arrow), characterizing the appearance of a white lung on ultrasound (A).