Pathology of the Respiratory System 3: Lung

Shannon Martinson, March 2016 http://people.upei.ca/smartinson/ VPM 222 Systemic Pathology

DISORDERS OF THE LUNG

Congenital

Pigmentary deposition

Circulatory Disturbances

Inflation disturbances

Pneumonia

Neoplasia

DISORDERS OF THE LUNG

Circulatory Disturbances

Congestion and Hyperemia

Hemorrhage

Thrombosis

Embolism

Edema

LUNG – CIRCULATORY DISTURBANCES

Pulmonary Edema

• Pulmonary edema occurs in many diseases as a terminal event preceding death • Characterized by accumulation of fluid in pulmonary interstitium and alveoli

1. Increased vascular permeability

(inflammation, vascular damage)

2. Increased hydrostatic pressure (cardiogenic edema - heart failure)

• Others causes are less common: Hypoproteinemia and Lymphatic Obstruction

Two main underlying mechanisms of lung edema are:

LUNG – CIRCULATORY DISTURBANCES

Pulmonary Edema

LUNG – CIRCULATORY DISTURBANCES

Pulmonary Edema

Increased vascular permeability Increased hydrostatic pressure

LUNG – CIRCULATORY DISTURBANCES

Pulmonary Edema Gross Findings

Froth oozing from nares

Froth in Trachea

Foam in Trachea Wet lungs / Distended interlobular septa

LUNG – CIRCULATORY DISTURBANCES

Pulmonary Edema Gross Findings

LUNG – CIRCULATORY DISTURBANCES

Pulmonary Edema Histologic Findings

Often accompanied by congestion

Pink fluid in alveolar spaces

Dilation of the lymphatics in the interlobular septa

Normal Fetal Lung

LUNG – INFLATION DISTURBANCES

Aeration

Club cells/Type II Pneumocytes Aeration

Normal Fetal Lung

LUNG – INFLATION DISTURBANCES

Pulmonary Surfactant

alveolus alveolus

LUNG – INFLATION DISTURBANCES

alveolus

• Incomplete expansion of the lung (or part of the lung) Atelectasis

• Abnormal and permanent enlargement of the aveoli with destruction of the walls. Emphysema

Normal

alveolus

Atelectasis

alveolus

LUNG – INFLATION DISTURBANCES

alveolus

Emphysema

Congenital (Neonatal)

Acquired

LUNG – INFLATION DISTURBANCES

Atelectasis

Meconium Obstruction

Neonatal distress syndrome

Lack of Surfactant

LUNG – INFLATION DISTURBANCES

Congenital Atelectasis

Meconium Obstruction

LUNG – INFLATION DISTURBANCES

Congenital Atelectasis

• Obstruction (exudate, parasites, etc).

• Compression of the lung parenchyma by space occupying mass

• Lack (degradation) of surfactant from inflammation

LUNG – INFLATION DISTURBANCES

Acquired Atelectasis

Compressive Atelectasis Obstructive Atelectasis

Acquired Atelectasis

LUNG – INFLATION DISTURBANCES

LUNG – INFLATION DISTURBANCES

Emphysema

1. Alveolar Emphysema

2. Interstitial Emphysema

3. Bullous Emphysema

• In animals, emphysema occurs: • 2◦ to pneumonia • 2◦ to heaves (RAO) • Agonally (cattle)

Normal Emphysema

Permanent enlargement of alveoli with destruction of alveolar walls (vs hyperinflation).

LUNG – INFLATION DISTURBANCES

Emphysema

Alveolar Emphysema

LUNG – INFLATION DISTURBANCES

Alveolar Emphysema Interstitial Emphysema

LUNG – INFLATION DISTURBANCES

Bullous Emphysema

LUNG – INFLATION DISTURBANCES

Bullous Emphysema

Gross Classification of Pneumonias in Domestic Animals

Texture/Distribution/Exudate

Suppurative Bronchopneumonia

Fibrinous Bronchopneumonia

Interstitial Pneumonia

Embolic Pneumonia

Granulomatous pneumonia

LUNG – PNEUMONIA

• Gross Findings

• Distribution:

• Cranioventral

• Texture:

• Firm

• Color:

• Red to grey

• Port of entry:

• Aerogenous

• Common etiologies:

• Bacteria (low pathogenicity)

• Mycoplasma spp

• Aspiration of bland material

Bovine lung

normal

LUNG – PNEUMONIA

Suppurative Bronchopneumonia

Erogenous

LUNG – PNEUMONIA

Suppurative Bronchopneumonia

• Cranioventral consolidation and dark pink to red colouration • Purulent exudate can be expressed from the airways on section

Gross Findings

LUNG – PNEUMONIA

Suppurative Bronchopneumonia

Histology

• Abscesses

• Fibrosis, pleural adhesions

• Bronchiectasis

LUNG – PNEUMONIA

Suppurative Bronchopneumonia

Sequelae

• Abscesses

• Fibrosis, pleural adhesions

• Bronchiectasis

LUNG – PNEUMONIA

Suppurative Bronchopneumonia

Sequelae

LUNG – PNEUMONIA

Fibrinous Bronchopneumonia (Pleuropneumonia)

• Gross Findings

• Distribution:

• Cranioventral

• Texture:

• Firm to hard

• Color:

• Red to yellow grey

• Yellow fibrin on the surface

• Port of entry:

• Aerogenous

• Common etiologies:

• Pathogenic bacteria

• Severe injury (toxic, aspiration)

LUNG – PNEUMONIA

Fibrinous Bronchopneumonia (Pleuropneumonia)

• On section: • Interlobular septa are

expanded • Tissue appears marbled

with coagulative necrosis of some lobules

Gross Findings

LUNG – PNEUMONIA

Fibrinous Bronchopneumonia (Pleuropneumonia)

• Sequestra

• Fibrosis, pleural adhesions

Sequelae

LUNG – PNEUMONIA

Interstitial Pneumonia

• Gross Findings

• Distribution:

• Diffuse

• Lungs fail to collapse and have rib imprints on the surface

• Texture:

• Elastic /meaty

• Port of entry:

• Aerogenous

• Hematogenous

• Common etiologies:

• Viruses

• Injury to the alveolar wall

• Viruses

• Toxins

• Sepsis

• Allergens

LUNG – PNEUMONIA

Interstitial Pneumonia

• Fibrosis

• Emphysema

Sequelae

LUNG – PNEUMONIA

Embolic Pneumonia

• Gross Findings

• Distribution:

• Multifocal

• Variably sized nodules often with hemorrhage

• Texture:

• Nodular

• Port of entry:

• Hematogenous

• Common etiologies:

• Endocarditis, ruptured hepatic abscesses, omphalophlebitis

• “Showering” of the lungs

LUNG – PNEUMONIA

Embolic Pneumonia

• Abscesses

Sequelae

LUNG – PNEUMONIA

Embolic Pneumonia

LUNG – PNEUMONIA

Granulomatous Pneumonia

• Gross Findings

• Distribution:

• Multifocal

• Variably sized nodules

• Firm dry exudate +/- mineral on section

• Texture:

• Nodular and firm to hard

• Port of entry:

• Aerogenous

• Hematogenous

• Common etiologies:

• Mycobacteria, Fungi, Parasites, Foreign material

LUNG – PNEUMONIA

Granulomatous Pneumonia

LUNG – PNEUMONIA

Granulomatous Pneumonia

LUNG – PNEUMONIA

Granulomatous Pneumonia

• Wasting (Cachexia)

Sequelae

A special thanks to Dr. Alfonso López for providing the

material for these lectures!