red hepatization

Following the congestion stage, the affected lobe undergoes red hepatization as alveolar capillaries leak RBCs along with neutrophils and fibrin into the airspaces, producing a solid red, liver-like consistency. This is classically associated with Streptococcus pneumoniae lobar pneumonia and presents with rusty/blood-tinged sputum, dullness to percussion, increased fremitus, and bronchial breath sounds over the consolidation. Microscopically, alveoli are packed with intact RBCs and neutrophils. It then transitions to gray hepatization as RBCs lyse. Both hepatization stages collectively define the consolidated phase of lobar pneumonia.