Pulmonary Congestion and Related Conditions

Pulmonary Congestion

• Passive accumulation of blood in pulmonary vessels and capillaries
• Often a result of left-sided heart failure
• Grossly appears as diffuse red discoloration of all pulmonary lobes, except cranial margins which appear thin and white
• Lung edema is a characteristic feature

Histology

• Heart Failure Cells: alveolar macrophages filled with hemosiderin are found within the alveoli
• Congested capillaries leak fluid and erythrocytes into the alveolar space, causing edema and intra-alveolar hemorrhages
• Red blood cells lyse and release hemosiderin, which is phagocytized by alveolar macrophages, forming "Heart Failure Cells"

Ruptured Pulmonary Aneurysm

• Large abscess erodes major pulmonary vessel

Abnormalites of Inflation

• Collapsed (Atelectasis)
• Overinflated (Emphysema)

Pulmonary Atelectasis

• Acquired atelectasis occurs when previously inflated alveoli lose air content
• Causes:
  • Complete airway obstruction
  • Pulmonary compression:
    • Tympany
    • Hydrothorax -Traumatic pericarditis
• Grossly:
  • Lung shows a meaty appearance (red and firm)
  • Lung is depressed relative to adjacent normal tissue

Pulmonary Emphysema

• Over inflation of alveoli with destruction of walls
• Causes:
  • Incomplete obstruction of bronchi or bronchiole (e.g., foreign body or exudate), interfering with expiration
• Alveolar emphysema is characterized by enlargement and rupture of the alveolar walls.