Lower respiratory tract infections are the most lethal transmissible diseases worldwide, causing around 3 million deaths per year [7].
Previously, six types of coronavirus had been identified that cause human disease: four cause mild respiratory symptoms, whereas the other two, Middle East respiratory syndrome (MERS) coronavirus and severe acute respiratory syndrome (SARS) coronavirus, have caused epidemics with high mortality rates [7].
In 2019, a new strain, called SARS-CoV-2, started circulating all over the word as a pandemic, causing the disease COVID-19 [6].
Imaging is confirmed to be critical in assessing severity and disease progression in COVID-19 infection [4].
Variety of imaging features seen while studying MSCT of chest of COVID-19 patients shows great similarity to that described in other coronavirus-associated syndromes.
Sensitivity and specificity of chest CT for COVID-19 are reported to range from 80 to 90% and 60 to 70%, respectively [8, 9].
In our study, we noted dyspnea was the commonest clinical symptoms which was in disagreement with the study done by Andrea et al. [10] who noted that fever was the most common symptoms in COVID positive patients, followed by cough and fatigue. Fever is 85.6%, cough is 68.7%, and fatigue is 39.4%.
According to the different radiological findings in the study population, it was noted that ground-glass opacification was the most common radiological finding 84%, followed by consolidation 60% which agrees with Ming et al. [11] who studied the imaging profile of the COVID-19 infection and agrees with Melina et al. [5] which showed that multifocal ground-glass opacities and consolidation were reported as main radiological features (Fig. 1).
The ground-glass and consolidative opacities were peripheral in most patients with lung findings (n = 42, 84%), while 6 patients had diffuse ground-glass changes and 2 patients showed peri-hilar distribution, which is matching with a study done by Ming et al. [11] who found that lung affection was peripheral in all patients with lung findings (100%), apart from one patient who had peri-hilar ground-glass changes in addition (Figs. 2 and 3).
Twenty-two patients showed lower zone predominance (44%), 18 patients showed equal distribution between the upper and lower zones (36%), and ten patients showed upper zone predominant changes (20%), which is partially agreeing with Ming’s study [11] who found that 44% of patients showed lower zone predominance, while 44% of patients showed equal distribution between the upper and lower zones and 16% of patients showed upper zone predominant changes and agrees also to the study done by Ho et al. [12], who demonstrated that the common CT findings of bilateral involvement, peripheral distribution, and lower zone dominance.
Reversed halo sign was seen in 3 cases (6%) which is agreeing with Ming et al. who stated that reversed halo sign was seen infrequently (Fig. 4).
We found coarsening of basal pulmonary interstitium in 8 cases (16%) which does not match with the study done by Shuchang et al. [13] who found GGO plus a reticular pattern in 62.9% of his patients (Fig. 5).
Curvilinear subpleural opacity was seen in 7 patients (14%) which is matching with studies by Wu et al. [14] and Li et al. [15] both reported around 20% of patients with COVID-19 demonstrated this sign, which might relate to pulmonary edema or fibrosis of COVID-19 (Fig. 6).
Crazy paving pattern was seen in 3 patients (6%) which is matching with many recent investigations reported 5~36% COVID-19 patients with crazy paving pattern in their studies [15, 16]. Furthermore, the presence of diffuse GGO, consolidation, and crazy paving pattern can be the signal of COVID-19 entering progressive or peak stage [17] (Fig. 7).
Pleural effusions, pericardial effusion, cavitation, mediastinal, and hilar lymph node enlargement were not seen in any of our patients which agree with Ming’s study [11] which declared that lung cavitation, discrete pulmonary nodules, pleural effusions, and enlarged lymph nodes were absent.
Since COVID/SARS and MERS are considered from the same viral family (coronavirus), imaging features of COVID-19, SARS, and MERS overlap, but still differences exist as well.
Unlike SARS, where initial chest imaging abnormalities are more frequently unilateral, COVID-19 is more likely to involve both lungs on initial imaging presented as bilateral peripheral subpleural scattered ground-glass opacities [5]. The majority of SARS positive patients show progressive multifocal distribution, in the follow-up imaging, of which 75% of patients show bilateral distribution [18], while MERS initial imaging tends to show multifocal airspace opacities in the lower lung zones which then progress to extend peri-hilar and upper lobar [19].
Pleural effusion is absent in COVID-19 patients while it is not rare in MERS and might be observed in 20–33% of affected individuals [5].
Centrilobular nodules and tree-in-bud are not characteristics of SARS or MERS [20], which is the same in COVID-19 according to our study.
Overall, the imaging findings are highly sensitive yet highly nonspecific and might overlap with the symptoms of H1N1 influenza, cytomegalovirus pneumonia, or atypical pneumonia. The acute clinical presentation and history of contact with a COVID-19-infected patient or history of recent travel should raise clinical suspicion for the diagnosis of COVID-19 [21].