Lung sequelae of COVID-19 with x-ray and CT: our experience
OBJECTIVES
-  To describe early and late lung sequelae of COVID-19 with x-ray and CT
-  To correlate imaging findings with clinical symptoms, lung function tests and risks factors
METHODS AND MATERIALS
Recovery from COVID-19 is variable. A non-negligible group of patients suffer from persistent clinical symptoms (breathless or cough) and/or functional lung impairment. This situation is known as “long COVID” and recently “post-acute sequelae of COVD-19 (PASC)”. There is not yet an agreement to establish the needed time to define this term. Chest x-ray and/or CT are usually performed in such cases.
We have reviewed imaging exams and clinical data in long COVID patients in our institutions (Hospital Universitario La Princesa and Hospital Universitario Fundación Alcorcón).
RESULTS
In chest x-ray loss of lung volume, linear and/or reticular opacities as well as ground glass opacities can be found.
The interpretation of CT is difficult in this disease due to the lack of histological correlation.
CT findings can be classified in three groups: 1) predominant ground glass opacities, 2) mixed ground glass and fibrotic-like pattern (parenchymal bands, reticular abnormalities, interlobular septal thickening…) and 3) predominantly fibrotic pattern (traction bronchiectasis and bronchiolectasis, architectural distortion). Findings of groups 1 and 2 may resolve or progress to fibrosis in follow-up studies.
A subset of patients with persistent symptoms do not show imaging abnormalities.
Predictors of post-covid lung disease include the extent of lung disease on CT and the severity of illness (measured by need of hospitalization, oxygen and mechanical ventilation). High inflammatory markers, older age, male sex, underlying co-morbidities, diagnosis of ARDS and mechanical ventilation are risk factors for fibrotic changes on CT. Previous lung fibrotic diseases may accelerate fibrosis in COVID patients. Persistent fibrotic changes often correlate with restrictive impairment on function tests.
CONCLUSION
Unfortunately, PASC is a novel entity that thoracic radiologist should know well and take it in account.
A CT is mandatory in patients with long-COVID disease. Ground glass opacities, reticular changes and traction bronchiectasis are common findings.
Early detection of fibrotic abnormalities should be desirable, as investigation of antifibrotic drugs are ongoing.
There is a long way ahead to determine post-COVID lung disease and research how to treat and prevent it.

**Lung sequelae of COVID-19 with x-ray and CT: our experience**
OBJECTIVES
-  To describe early and late lung sequelae of COVID-19 with x-ray and CT
-  To correlate imaging findings with clinical symptoms, lung function tests and risks factors
METHODS AND MATERIALS
Recovery from COVID-19 is variable. A non-negligible group of patients suffer from persistent clinical symptoms (breathless or cough) and/or functional lung impairment. This situation is known as “long COVID” and recently “post-acute sequelae of COVD-19 (PASC)”. There is not yet an agreement to establish the needed time to define this term. Chest x-ray and/or CT are usually performed in such cases.
We have reviewed imaging exams and clinical data in long COVID patients in our institutions (Hospital Universitario La Princesa and Hospital Universitario Fundación Alcorcón).
RESULTS
In chest x-ray loss of lung volume, linear and/or reticular opacities as well as ground glass opacities can be found.
The interpretation of CT is difficult in this disease due to the lack of histological correlation.
CT findings can be classified in three groups: 1) predominant ground glass opacities, 2) mixed ground glass and fibrotic-like pattern (parenchymal bands, reticular abnormalities, interlobular septal thickening…) and 3) predominantly fibrotic pattern (traction bronchiectasis and bronchiolectasis, architectural distortion). Findings of groups 1 and 2 may resolve or progress to fibrosis in follow-up studies.
A subset of patients with persistent symptoms do not show imaging abnormalities.
Predictors of post-covid lung disease include the extent of lung disease on CT and the severity of illness (measured by need of hospitalization, oxygen and mechanical ventilation). High inflammatory markers, older age, male sex, underlying co-morbidities, diagnosis of ARDS and mechanical ventilation are risk factors for fibrotic changes on CT. Previous lung fibrotic diseases may accelerate fibrosis in COVID patients. Persistent fibrotic changes often correlate with restrictive impairment on function tests.
CONCLUSION
Unfortunately, PASC is a novel entity that thoracic radiologist should know well and take it in account.
A CT is mandatory in patients with long-COVID disease. Ground glass opacities, reticular changes and traction bronchiectasis are common findings.
Early detection of fibrotic abnormalities should be desirable, as investigation of antifibrotic drugs are ongoing.
There is a long way ahead to determine post-COVID lung disease and research how to treat and prevent it.

Lung sequelae of COVID-19 with x-ray and CT: Our experience

The Winter Course 2021 covers a variety of topics from basics in interstitial lung disease, infections including Covid-19, malignancies, lung cancer screening, and artificial intelligence. The combination of topics is aimed to serve as a good introduction to radiologists embarking on a career in thoracic imaging as well as a solid refresher for experienced thoracic radiologists.

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