3.3. Chest imaging
Radiological examinations are of great importance in the early detection
and management of COVID-19. According to current experience, lung
imaging manifests can be found earlier than clinical symptoms, so
imaging examination is vital in preclinical
screening(Sohrabi et al., 2020).
Therefore, suspected cases should undertake chest examination as soon as
possible.
In early stage, multiple small patchy shadows and interstitial changes
were detected in the extra pulmonary zone. And then, it developed into
multiple ground-glass infiltration (D.
Wang et al., 2020).
In
severe and critically cases,
lung
lesions usually involved most commonly 4-5 lobes in the bilateral lower
and upper lobes.
The
first report of COVID-19 patients described that bilateral lung
involvement was detected in 80% of patients, and consolidative pattern
changes were always observer in most patients in intensive care unit
(ICU), but ground-glass pattern always showed in patients not in the
ICU(Bernheim
et al., 2020). Shi et al. analyzed the CT changes and found that most
patients even the asymptomatic patients showed dynamic changes from
focal unilateral to diffuse bilateral ground-glass opacities and then
progressed to consolidations within 1-3
weeks(X.-W. Xu et al., 2020). In general,
combining assessment of imaging features with clinical and laboratory
findings can facilitate diagnosis of COVID-19 pneumonia and evaluate
severity of the disease.
4.Thepathological
changes in COVID-19 patients
A
recent study reported the biopsy results from two patients who underwent
surgery for malignancy and then were found to have been infected with
SARS-CoV-2, which provided first opportunities to study the pathology of
COVID-19. It revealed that the lungs of patients exhibited edema,
proteinaceous exudate, focal reactive hyperplasia of pneumocytes with
patchy inflammatory cellular infiltration, and multinucleated giant
cells, but hyaline membranes were not
prominent(Tian et al., 2020). This study
may describe early phase changes of the lung pathology of COVID-19
pneumonia. After that some academics performed autopsy from 12 dead
patients and the results were released by the national health
commission. The histopathological changes for different organs are
summarized below:
Lung The lungs showed evident multi-pulmonary consolidation,
acute interstitial inflammatory infiltrates and congestion in the
alveolar septae. The lumina of alveoli and bronchioles were variably
filled with proteinrich oedema fluid, erythrocytes, cellular debris and
lymphocytes. The exudation cells were mainly mononuclear, macrophages
and multinucleated giant cells. Type II alveolar epithelial cells
proliferated obviously with Inclusion bodies inside. The blood vessel of
the alveolar septum had congestion and edema, in which the infiltration
of mononuclears lymphocytics, and intravascular hyaline thrombosis can
be seen. Focal hemorrhage and necrosis of the lung tissue caused
hemorrhagic infarction. Diffuse interstitial pulmonary fibrosis would be
presented with the disease progress.
Bronchial
epithelial cells were denaturation, necrosis and defluvium. Mucus plugs
were visible in the bronchial lumen. Due to over-inflation of the
alveoli, a small number of the alveolar septum was broken, or the cysts
were formed. SARS-CoV-2 particles could be observed in the cytoplasm of
bronchial mucosal epitheliums and type II alveolar epithelial cells
under an electron microscope. Immunohistochemical staining showed that
some alveolar epitheliums and macrophages were positive for SARS-CoV-2
antigens. RT-PCR was positive for SARS-CoV-2 nucleic acids.
Immune systemThe
volume of spleen decreased
significantly
and the number of lymphocytes was significantly
reduced.
There were focal patchy hemorrhages, necrosis and proliferation and
phagocytosis of macrophages in the splenic tissue, with atrophy of white
pulp lymphoid aggregates. The number of lymphocytes decreased obviously,
and necrosis was visible in lymph nodes. Immunohistochemical staining
showed that CD4 + T and CD8 + T cells were reduced in the spleen and
lymph nodes. The number of three cell lines in the bone marrow was
reduced.
Cardiovascular system There was
notable
degeneration and necrosis
in
the myocardial cells, and a few monocytes, lymphocytes and neutrophils
infiltrated in the interstitium. Endothelial shedding, endovascular
inflammation and thrombosis were visible in the blood vessel.
Liver and gallbladder The volume of the liver increased and its
color was dark red. there are degeneration of hepatocytes, congestion of
hepatic sinus, focal necrosis with neutrophil infiltration and
microthrombosis, which feature the repeated interchange of these kinds
of pathological course. The gallbladder was filled with bile.
Kidney There was proteinaceous exudate in the glomerular
cavity
and degeneration and necrosis in renal tubular epitheliums. Hyperemia,
microthrombus and focal fibrosis can be observed in the renal
interstitium.
other
organs Within the cerebrum, there was evidence of ongestion, edema,
mild neuronophagia and some cases showed neurons degeneration. There
were focal necrosis in the adrenal glands. Mucosal epitheliums of the
esophagus, stomach and intestine had varying degrees of the
degeneration, necrosis and shedding.
5. Diagnosis ofCOVID-19
As the number of cases increased rapidly, the first task for the
clinical diagnostic workflow is to identify the suspected cases and
isolating them immediately, which is critical to cutting off the source
of infection. The National Health Commission of China released the
Diagnosis
and Treatment Scheme for Novel Corona Virus Pneumonia (Trial) Edition.
Patients comply any item of the epidemiological history and any two
items of the clinical manifestations, or comply 3 items of the clinical
manifestations mentioned above can be considered as the suspected cases(Table.2) . Based upon the evidence from clinical research, the
detection of SARS-CoV-2 nucleic acids in nasopharyngeal swabs, sputum,
lower respiratory tract secretions and SARS-CoV-2-specific antibodies
(IgM and IgG) may be the final etiology diagnosis for the confirmed case
(Table.2 ). In addition, COVID-19 can be divided into four
classes: mild, moderate, severe, and critical according to the severity
of symptoms (Table 3 ). There are some clinical signs and
symptoms closely related to the severity of the confirmed cases
(Table 4 ).