Consolidation of chest CT
Case 238
【Progress】
Treatment by steroid and heparin made his symptoms and laboratory data gradually improved. Ten days after admission, he was discharged. The virus gene of his pathogen was revealed to be variant SARS-2
【Discussion】
It is known that pneumonia by bacterial infection induces consolidation in pulmonary area on chest radiograph and/or CT (1). It was supposed that consolidation consists of accumulation of bacteria and neutrophils. In general, laboratory test supports this concept because in case of bacterial inflammation, it usually shows the marked proliferation of neutrophils in whole blood.
Meanwhile, it is known that pneumonia by virus infection induces ground glass opacity in pulmonary area on chest radiograph and/or CT. In general, laboratory test in virus infection reveals normal count of white blood cells including an increase count of monocyte and lymphocytes (2-4). Before on February 28th 2021, chest CT in patients with COVID19 showed ground glass opacity without consolidation. The counts of lymphocytes and monocytes of these patients tend to increase. Thereafter, along with emergence of variant COVID19, consolidation on chest CT came to be found on chest CT (2-4). In this situation, the percentage of lymphocytes and monocytes decrease, while that of neutrophils increase. It becomes clear that consolidation appears on chest CT with the increase count of neutrophils despite of no bacterial infection. That is corresponded to time when PO2 saturation worsens in patients with variant COVID19 (5). One of the functions of neutrophils is to increase permeability of vessels, inducing serum flow into alveolar spaces, impeding O2-CO2 exchange (6-10). In case of under control of lymphocyte and monocyte, function of neutrophils is repressed. Accompanied with the decrease counts of lymphocytes and monocytes, namely the lowering of governance by lymphocytes, neutrophils come out, inducing to increase the permeability of the vessels. Lymphocytes and monocytes were dead worn out to battle with virus since momentum of variant COVID19 exceeds primary defense power. Then, neutrophils appear to assist and phagocyte virus with permeability of vessels, inducing serum flowing out alveolar space, resulting in suddenly marked decrease of PO2 and consolidation on chest CT.
Before variant COVID 19, fibrotic change or absorption process appears following ground glass opacity. In time of variant COVID 19, fibrotic change appears following consolidation. Both fibrotic change and consolidation are more dense opacities than ground glass on CT. It is important to interpret the differentiation between consolidation and fibrosis since consolidation implies decrease of PO2 and necessitate O2 inhalation, while fibrosis implies absorption mechanism. In case of variant COVID19, fibrosis delays probably fibroblasts are infected and destructed, implying absorption and repairing are disordered.
【Summary】
We presented a sixty-year-old male with variant COVID19. Nine days after the onset, he got fever of 39 C and felt disorder of breathing, falling to 92% of PO2 saturation. Laboratory test revealed: white blood cell 5460/mm3, neutrophils 87.9%, lymphocytes 6.6%, monocytes 3%. Chest CT showed multiple consolidation in the marginal area of both lobes. It is borne in mind that ground glass is usually shown on chest CT in patients with original COVID19, while consolidation in those with variant COVID19. Ground glass is accompanied with the increase of lymphocytes and monocytes, while consolidation is done with the increase of neutrophils. One of the functions of neutrophils is increased permeability of the vessel: serum flowing out to alveolar space. It implies the decreased space for O2-CO2 exchange, inducing the decrease of PO2 saturation. Although consolidation and fibrosis are shown to be thickened radio-opacity, it is important to interpret the differentiation between consolidation and fibrosis since consolidation implies decrease of PO2 and necessitate O2 inhalation, while fibrosis implies absorption mechanism.
【References】
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2021.7.21