Pulmonary findings in COVID-19: radiology correlates with the histopathological post-mortem findings in patients with fatal acute disease

Background Progressive respiratory failure is the leading cause of death in patients with severe COVID-19. Histopathological findings in acute severe COVID-19 are foremost based on post-mortem findings. On computed tomography (CT), acute COVID-19 pneumonia is characterized by ground-glass opacities (GGOs) and, later, by a crazy-paving pattern (CPP) and consolidations. Purpose To investigate if CT patterns corresponded to histopathological post-mortem findings. Material and Methods Eight patients were identified with a chest CT performed between testing positive for COVID-19 and death. CT images, histological slides, and medical records were retrospectively reviewed. The lungs were photographed during the gross investigation to ascertain the exact position of the tissue blocks in relation to the relevant anatomical structures. Each slide was compared side by side with the in vivo chest CT pattern on the corresponding site. Results At CT, the most predominant finding was GGOs, present in all eight cases. CPP was observed in 6/8 (75%) patients, and consolidation in 7/8 (87.5%) patients, both predominantly located in the lower lung zones. In 5 (62.5%) patients, so-called fibrotic-like changes were present. In four patients with CT angiogram, no findings of pulmonary thromboembolism were present. At autopsy, all patients demonstrated macroscopic consolidation, while pleural effusion was seen in 2 (25%) cases. Microscopically, edema was present in all cases, hyaline membranes in 7/8 (87.5%) cases, but no signs of acute interstitial inflammation were observed. Thromboembolic findings were evident in 4 (50%) patients, of whom two were negative on CT and 3 (37.5%) cases had fibrosis. Conclusion The results demonstrate a clear association between radiological signs of GGO, consolidation and features of organizing pneumonia to microscopical signs of edema and diffuse alveolar damage. However, fibrotic-like changes and thromboembolism in the small vessels had a poorer compliance.