What are the Histological Features of Diffuse Alveolar Damage?

Histologically, DAD shows distinct features in both its exudative and organizing phases.

Exudative Phase: The predominant features include alveolar septal edema, fibrin-rich hyaline membranes lining the alveolar ducts, and interstitial inflammation. The alveolar spaces may appear filled with proteinaceous fluid and cellular debris.
Organizing Phase: This phase shows fibroblastic proliferation within the alveolar septa, leading to the formation of fibroblastic foci. There is also evidence of type II pneumocyte hyperplasia and the presence of myofibroblasts producing collagen.