Lobar pneumonia - Erler Zimmer

Lobar pneumonia - Erler Zimmer

Clinical History

No clinical history is available for this specimen.

Pathology

The specimen is a parasagittal section of the right lung, clearly displaying the boundaries between the three lobes. The entire upper and middle lobes exhibit congestion and hyperaemia, resulting in a darker appearance. Smaller foci of similar nature are observed in the left lung.

Further Information

Lobar pneumonia is characterized by inflammatory exudate within the intra-alveolar space, leading to consolidation that affects a large and continuous area of a lung lobe. This form of pneumonia, one of the two anatomic classifications along with bronchopneumonia, presents classical red 'hepatization' or consolidation of the lung parenchyma in this specimen. The red appearance is due to vascular congestion with extravasation of red cells into alveolar spaces, along with increased neutrophils and fibrin. The resulting filling of airspaces by the exudate creates a gross appearance of solidification or consolidation of the alveolar parenchyma, resembling the cut surface of the liver, hence the term "hepatization."

The most common causative organisms for lobar pneumonia include Streptococcus pneumoniae (pneumococcus), Haemophilus influenzae, and Moraxella catarrhalis. Tubercle bacillus (Mycobacterium tuberculosis), Legionella pneumophila, and Klebsiella pneumoniae may also lead to lobar pneumonia in certain cases. Lobar pneumonia can be community-acquired, occur in immunosuppressed patients, or manifest as a nosocomial infection. Posteroanterior and lateral chest radiographs typically show an entire lobe as radiopaque with no evidence of air, indicative of lobar pneumonia.