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RADIOLOGICAL INVESTIGATIONS FOR COVID -19

Chest X-ray /CT findings classified as: 

1.Classic
       • Ground glass opacities/consolidation/ crazy paving/ reverse halo
       • Peripheral region / multiple / bilateral / lower lobe > upper lobe
2. Probable
Bronchocentric and peripheral consolidation / less of ground-glass opacities and reverse halo.
3. Indeterminate
Not so classic / some changes / but not normal.
4. Non-Covid-19
If initial findings are lobar pneumonia / effusion / pneumothorax /pulmonary edema.
5.Normal:
No findings / But COVID -19 is not excluded.
 
Chest-films can be useful in the follow-up of the disease. These x-rays are of a patient with COVID-19. On admission to the hospital, the chest film was normal. Four days later the patient is on mechanical ventilation and there are bilateral consolidations on the chest film.

How to quantify the changes? 

Based on the severity:

Mild: 
Ground glass opacities (<3 cm in maximum diameter).

Moderate/Severe: 
Ground glass opacities (more than 3 focal abnormalities or maximum diameter >3 cm)/ mixed with early consolidation. 

Severe:
Diffuse ground-glass opacities, consolidation with architectural distortion. Ground-glass opacification and consolidation in the right upper lobe and left lower lobe (arrows) in a patient with COVID 19 infection.

Typical CT findings:

Classic COVID – 19 
• Peripheral ground glass opacities
• Crazy paving may be present
• Organising pneumonia 

Probable Covid – 19
• Bronchocentric and nodular organizing pneumonia, with air bronchogram.
• No ground glass opacities.

Non - COVID -19
• Lobar pneumonia
• Cavitating infections 
• Tree in bud changes 
• Extensive ground glass opacities noted involving both the lung fields.

Based on progression:

• Ultra-early stage (no symptoms) – Ground glass opacities, nodules, patchy consolidation.
• Early stage (symptoms present) – Single or multiple ground-glass opacities with or without septal thickening.
• Rapid progressive stage (3-7days) – Large consolidation with air bronchogram.
• Consolidation stage (7-14 days) – Consolidation areas start to reduce in size and density. 
• Resolving (14-21 days) – Dispersed and reducing consolidation, linear and reticular opacities and interlobular septal thickening. 
 
(A) Day 3 after symptom onset: multifocal consolidations affecting the bilateral, subpleural lung parenchyma.

(B) Day 7: the lesions had increased in extent and the density became heterogeneous, with internal bronchovascular bundle thickening.

(C) Day 11: previous opacifications being dissipated into ground-glass opacities and irregular linear opacities.

(D) Day 18: the further resolution of the lesions.

Note:

• A typical Covid-19 patient’s CT finding is bilateral, peripheral, multi-lobar areas of ground glass opacities and consolidation.  
• CT Chest is now the radiological investigation of choice for patients suspected having Covid-19 infection.

Ultrasound Findings of Covid -19 pneumonia:

Typical Finding

• Thickening of the pleural line with pleural line irregularity.
• B-lines in a variety of patterns including focal, multifocal and confluent.
• Consolidation patterns, including multifocal small, non-translobar with air bronchogram.
• Appearance of A-lines during recovery phase.
• Pleural effusions are uncommon.

Progression of Covid-19 pneumonia

• Focal *B-lines is the main feature of the early stage and mild infection.
• Alveolar interstitial syndrome is the main feature in the progressive stage and in critically ill patients.
• A-lines can be found in the convalescence stage.
• Pleural line thickening with uneven B-lines can be seen in patients with pulmonary fibrosis. 

* Kerley A line:  These are 2-6 cm long oblique lines that are <1 mm thick and course towards the hila. They represent thickening of the interlobular septa

* Kerley B line:  These are thin lines 1-2 cm in length in the periphery of the lung(s). They are perpendicular to the pleural surface and extend out to it. They represent thickened subpleural interlobular septa and are usually seen at the lung bases. 

Note: Severity is assessed based on coalescent B-lines and the presence / size of the consolidation.
 
A. Mild ground-glass opacities on CT corresponding to scattered B lines in ultrasound images.
B. Confluent ground-glass opacities on CT correlates to coalescent B lines.
C. With more severe disease, small peripheral areas of consolidation seen on the ultrasound images.
D. In severe form, the volume of consolidation increased.

Limitations of lung ultrasonography:

•    It cannot detect lesions that are deep within the lung.
•    The lung abnormality which are extended to the pleural surface are only clearly visible.

Note:  The information in this article is based on various case-based studies conducted around the world and webinar information from various radiologists.  The purpose is to circulate the information to the maximum possible.

Dr. Vivin Cherian Kailath, MBBS, MD
Radiologist