Pathomorphological changes in the lungs in severe COVID-19

Abstract

Background. The study of pathogenesis and the search for factors that lead to mortality from severe COVID-19 and disability due to post-COVID interstitial lung disease with permanent physiological and functional deficits is an urgent and unsolved problem today. The purpose was to investigate lung histopathology in patients who died of severe COVID-19 in the acute and post-acute period of the disease, and to determine the significance of histological changes in the lung parenchyma depending on gender, duration of the disease, and the use or non-use of respiratory support. Materials and methods. The study included the results of lung sample analysis in patients with severe COVID-19 who died from June to December 2020 (n = 10) and from January to December 2021 (n = 21). An autopsy was performed in 61.3 % of patients who died in the acute period of the disease (up to the 28th day), and in 38.7 % of those who died in the post-acute period (day 29–84). Respiratory support was used in 58 % (n = 18) of cases in the acute period. Results. Patients with severe COVID-19 who did not survive the acute period of the disease (its average duration was 17.31 days, the average age of the deceased was 66.1 years) and the post-acute period (the average duration of the disease was 43.22 days, the average age of the deceased was 67.8 years) had the following: the presence of hyaline membranes in 70.9 %, capillary stasis in 77.4 %, organizing pneumonia in 41.9 %, pulmonary fibrosis in 32.2 %, hemorrhages in 38.7 %, small vein thrombosis in 25.8 %, histospecific signs of bacterial and fungal co-infection in 16.1 and 3.2 %, respectively, diffuse alveolar damage in 90.3 % of cases (with acute fibrinous and organizing pneumonia in 9.6 %). Conclusions. The risk of capillary stasis is significantly higher in the post-acute than in the acute period of the disease (p = 1.7454). No statistically significant correlation was found between the acute (p = 0.359) and post-acute (p = 0.146) periods and the risk of pulmonary fibrosis. Also, no significant relationship was detected between the use of respiratory support and recorded pulmonary fibrosis in the acute (p = 0.238) and post-acute (p = 0.302) periods. It was found that the histopathological signs of hemorrhages in the lungs are the same in both periods compared to the small vein thrombosis whose risk in the acute period is significantly higher than in the post-acute one (p = 0.05). The risk of bacterial co-infection in the acute period of the disease is significantly lower than the probability of its absence (p = 0.001). The risk of a fatal outcome in the acute period of the disease among men is significantly higher than among women (p = 0.05), while in the post-acute period, there is no statistically significant dependence on gender.