COVID-19 pneumonia: current evidence of chest imaging features, evolution and prognosis

Abstract

COVID-19 pneumonia represents a global threatening disease, especially in severe cases. Chest imaging, with X-ray and high-resolution computed tomography (HRCT), plays an important role in the initial evaluation and follow-up of patients with COVID-19 pneumonia. Chest imaging can also help in assessing disease severity and in predicting patient's outcome, either as an independent factor or in combination with clinical and laboratory features. This review highlights the current knowledge of imaging features of COVID-19 pneumonia and their temporal evolution over time, and provides recent evidences on the role of chest imaging in the prognostic assessment of the disease.

Keywords: COVID-19 pneumonia; Chest X-ray; Evolution; High-resolution computed tomography; Imaging findings; Prognosis.

Fig. 1

a Patient with COVID-19 pneumonia. The CT scan shows a crazy-paving pattern with typical predominant subpleural and bilateral distribution at the lung bases; note the presence of "enlarging vessel" sign within the areas of increased lung density (arrows). b Patient with H1N1 influenza-associated pneumonia. The CT scan shows multifocal small areas of consolidation and perilobular opacities with bilateral subpleural distribution at the lung bases, associated with some GG areas in the left lower lobe; note the normal caliber of pulmonary vessels in the proximity of the pulmonary abnormalities (arrowheads)

Fig. 2

CT scans of a patient with COVID-19 pneumonia demonstrating the typical evolution of the disease by phases. a In the early phase, GG opacities are the predominant finding. b 10 days after the onset of symptoms (progressive to peak phase) more extensive GG areas with crazy paving appearance and typical distribution at the lung periphery are observed. c One week later, GG areas decline and lead to the appearance of multifocal consolidation with mild parenchymal distortion

Fig. 3

Bedside chest radiograms of a patient with a severe condition of COVID-19 pneumonia showing the temporal lung changes from the early phase (a), characterized by bilateral interstitial opacities with peripheral mid-lower lung distribution, to the peak phase (b) with bilateral and more extensive confluent alveolar opacities. Note the presence of endotracheal tube and central venous catheter in both radiographs

Fig. 4

Axial HRCT scans of COVID-19 pneumonia in the absorption phase. Image in b nicely demonstrates a decrease in density of the multifocal GG opacities observed in a, with a more extensive bilateral lung involvement (“tinted” sign)

Fig. 5

Axial CT scans of a COVID-19 patient with acute pulmonary embolism (arrowhead in b), showing the temporal evolution of the lung abnormalities till the late phase. CT scans in a and b were performed 16 days after the onset of symptoms; CT scans in c and d 30 days after; CT scans in e and f 45 days after. Note the progressive reduction of the areas of consolidation and GG—more extensive in the left lung—and the appearance of fibrotic changes with traction bronchiectasis/bronchiolectasis and irregular interstitial thickening in the lingula (arrows in c and e) and in the left lower lobe (arrow in f), mainly in the area of the previously detected lung infarction (arrow in d)

Fig. 6

HRCT scans from the upper (a), middle (b), and lower (c) zones in a 54-year-old man who developed a severe course of COVID-19 pneumonia. The total CT severity score is 30, based on the scoring system proposed by Yuan et al. [64]: a right upper, 3 (consolidation) × 3 (extent 50–75%); left upper, 3 (consolidation) × 2 (25–50%); b right middle, 3 (consolidation) × 3 (50–75%); left middle, 2 (ground-glass) × 1 (< 25%); c right lower, 2 (ground-glass) × 1 (< 25%); left lower, 2 (ground-glass) × 1 (< 25%)

Fig. 7

Bedside chest X-ray performed at the emergency department admission in a 62-years-old male affected by COVID-19 pneumonia (a), showing a Brixia score of 9 [67]. Note that the upper line is drawn at the level of the inferior wall of the aortic arch, while the lower line is drawn at the level of the inferior wall of the right inferior pulmonary vein. Based on the chest X-ray severity score (≥ 8) and age (≥ 50 years-old), this patient had an increased risk of developing a severe disease course. Indeed, the chest X-ray performed 6 days later (b) depicts a clear disease progression, with increase in density and extent of the abnormalities in both lungs. Lately, the patient recovered after ICU admission