Which of the following is the most characteristic feature of Adult Respiratory Distress Syndrome (ARDS)?

Both Adult Respiratory Distress Syndrome (ARDS) and Acute lung injury(ALI) are associated with inflammation associated-increases in pulmonary vascular permeability, oedema and epithelial cell death. The histologic manifestation of these diseases is diffuse alveolar damageIn the acute stage, the lungs are heavy, firm, red, and boggy. They exhibit congestion, interstitial and intra-alveolar oedema, inflammation, fibrin deposition, and diffuse alveolar damage.Ref: Robbins 9e pg: 673