Pulmonary Pathology Quiz

Pulmonary Congestion

• Passive accumulation of blood in pulmonary vessels and capillaries
• Often a result of heart failure (Left Side)
• Diffuse red discoloration of all pulmonary lobes, except cranial margins
• Lung edema
• HEART FAILURE CELLS within the alveoli (alveolar macrophages filled with hemosiderin)
• Congested capillaries escape Fluid and erythrocytes into the alveolar space
• Edema and intra-alveolar hemorrhages occur
• RBCs lysis and releases hemosiderin
• Hemosiderin is phagocytized by alveolar macrophages ("Heart failure cells")

Ruptured Pulmonary Aneurysm

• Large abscess erodes major pulmonary vessel

Abnormalties of Inflation

• Collapsed (Atelectasis)
• Overinflated (Emphysema)

Pulmonary Atelectasis

• Previously inflated alveoli lose their air content
• Causes:
  • Complete airway obstruction
  • Pulmonary compression
    • Tympany
    • Hydrothorax
    • Traumatic pericarditis
• Grossly:
  • Lung shows a meaty appearance (red and firm)
  • Depressed in relation to the adjacent normal

Pulmonary Emphysema

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

Suppurative Bronchopneumonia

• Typically found in the cranioventral region of the lungs.
• Has a firm texture.
• Color changes from red (acute) to grey (chronic).
• Cut surface reveals purulent exudate within the bronchi.
• Enters the body through the air (aerogenous).
• Common causes include bacteria (low-grade pathogenicity), Mycoplasma, and aspiration of bland material.
• Often leads to cranioventral abscesses and bronchiectasis.

Fibrinous Bronchopneumonia

• Found in the cranioventral region.
• Has a hard texture.
• Color changes from red to yellow to grey.
• Fibrin is present on the pleural surface.
• Cut surface shows fibrin and necrosis.
• Enters the body through the air (aerogenous).
• Caused by highly pathogenic bacteria producing exotoxins like Mannheimia haemolytica and Actinobacillus pleuropneumoniae.
• Can also be caused by harsh aspirated materials.

Interstitial Pneumonia

• Found throughout the lungs (diffuse).
• Has an elastic texture.
• Cut surface appears meaty.
• Gross features include rib imprints and lungs that fail to collapse when the thorax is opened.
• Can enter the body through the air (aerogenous) or the bloodstream (hematogenous).
• Caused by viruses, toxins, type III hypersensitivity reactions, and toxicants.
• Damage is centered in the alveolar wall, affecting the endothelium or pneumocytes.
• Characterized by thickened alveolar walls.
• Often difficult to diagnose visually.

Granulomatous Pneumonia

• Found in multiple areas (multifocal).
• Has a nodular texture (without pus).
• Cut surface contains granulomas.
• Enters the body through the air (aerogenous) or the bloodstream (hematogenous).
• Caused by Mycobacterium spp., systemic mycoses, parasitic ova, trapped food particles (starch), and dead parasites.

Embolic Pneumonia

• Found in multiple areas (multifocal).
• Has a nodular texture.
• Enters the body through the bloodstream (hematogenous).
• Color is red when acute and pale when chronic.
• Caused by:
  • Rupture of hepatic abscesses into the vena cava in cattle.
  • Vegetative endocarditis (right side of the heart).
  • Jugular thrombosis.
  • Embolic foreign bodies (hair, septic emboli, etc.).

Laryngeal Hemiplegia

• The left cricoarytenoid muscle, supplied by the left laryngeal nerve, pulls the arytenoid cartilage away during inspiration
• Damage to the left laryngeal nerve causes atrophy of the left cricoarytenoid muscle, leading to the cartilage dropping and narrowing the larynx
• This narrowing causes a noisy inhalation, known as roaring
• Horses with this condition are called roarers

Necrotic Laryngitis (Calf Diphtheria)

• Affects the pharynx, larynx, and oral cavity of calves
• Caused by Fusobacterium necrophorum, a normal flora bacterium
• Calves stressed by dust or a virus can develop damage to their laryngeal mucosa
• Leads to the formation of a fibrinonecrotic membrane (also known as diphtheritic membrane or fibrinous membrane)

Tracheitis

• Inflammation of the trachea
• Common in cattle
• Can be caused by:
  • IBR (Infectious Bovine Rhinotracheitis)
  • BRSV (Bovine Respiratory Syncytial Virus)
  • PI-3 (Parainfluenza Virus 3)

Parasitic Bronchitis

• Most common forms:
  • Dictyocaulus viviparus (in bovines)
  • Dictyocaulus filariae (in ovines)
• Causes inflammation of the bronchioles, known as bronchiolitis

Bronchiectasis

• Dilation of the bronchial lumen

Equine Heaves

• Also known as Equine COPD (Chronic Obstructive Pulmonary Disease) or Equine Asthma
• An allergic disease in horses
• Caused by inhalation of dust and allergens
• Results in mild bronchiolar inflammation and severe goblet cell metaplasia, leading to increased mucus production and airway obstruction
• Grossly:
  • Difficult expiration, leading to compensatory hypertrophy of the abdominal muscles (heave line)
  • Pulmonary emphysema
• Microscopically:
  • Severe Bronchiolar Goblet Cell Metaplasia
  • Mucus Plugs In The Lumens
  • Presence of Some Inflammatory Cells