Pathology of the respiratory system (Castleman) Flashcards
Bronchi
anatomy
- Have cartilage and glands in their walls
- cartilage maintains patency; prevents collapse
- Thick connective tissue prevents infection spread into surrounding alveolar parenchyma
- Chronic inflammation results in dilation
- Changes in diameter increases resistance markedly
Bronchi
Cytodynamics of Epithelial repair
- Cytodynamics of Epithelial repair
- ciliated cells are terminally differentiated
- epithelial regenerative capacity
- mucous cells
- basal cells
- other nonciliated cells
Bronchiole
anatomy
- No cartilage or glands in walls
- airway patentcy maintained by tethering support of interalveolar septa on bronchiolar wall
- Thin connective tissue in wall allows infection spread to surrounding alveoli
- Chronic inflammation results in stenosis of lumen
Broncioles
cytodynamics of Epithelial repair
- Ciliated cells are terminally differentiated
- Epithelial regenerative capacity
- Mucous cells
- Nonciliated (Clara cells)
- Rich in cytochrome monooxygenase enzymes
Pulmonary lobue
- Primary lobule (Acinus)
- pulmonary tissue supplied by terminal bronchiole
- supplied by terminal brionchiole
- Secondary lobule
- composed of many primary lobules
- constitute grossly visible lobules
Interalveolar septa
- Epithelial cells
- type 1
- type 2
- surfactant
- stem cells
- Capillary endothelium
- Fibroblasts
- elastin
- collagen
- Macrophages
Type 1 epithelial cells
- Large surface area
- susceptible to damage
- incapable of division
Type 2 epithelial cells
- cuboidal
- produces surfactant
- produces other mediators
- effect epithelial repair
Which of the followig is not a stem cell for epithelial repair in bronchi and/or bronchioles (which cells are terminally differentiated)?
- A. Mucous cells
- B. Ciliated Cells
- C. Nonciliated cells
- B. Ciliated cells are terminally differentiated and can’t divide
Which of the following serve as stem cells for epithelial repair in the interalveolar spetum?
- A. Type 1 alveolar epithelial cells
- B. Type 2 alveolar epithelial cell
- C. Mucous cell
- B. Type 2 alveolar epithelial cells
*With pulmonary carcinoma it’s the type 2 cells that usually divide uncontrollably
Bronchitis and Bronchiolitis
- Definition
- Inflammation of bronchi and bronchioles
- Causes
- infectious
- viral
- bacterial
- fungal
- parasitic
- Toxic
- 4-ipomeanol and other plant toxins
- Hypersensitivity
- infectious
Bronchitis and Bronchiolitis
Functional Consequences
- Increases airway resistance
- airway obstruction
- airway wall thickening, accumulation of exudate
- hypoxemia
- ventilation/perfusion abnormalities
- airway obstruction
- Decrease mucociliary clearance
- predispose to secondary bacterial infection
Bronchitis and Bronchiolitis
Sequelae
- Resolution and epithelial repair
- Extension to alveoli
- Pneumonia
- Chronic localized inflammation
- Bronchi: Bronchiectasis
- Bronchioles: Bronchiolitis obliterans
- Post-obstructive atelectasis
Bronciectasis
Definition
Pathogenesis
- Definition
- Dilation of bronchi behond normal physiological limits due to destruction of the bronchial wall
- Pathogenesis
- Chronic infection
- usually bacterial
- Neutrophil-mediated tissue destruction
- destruction of glands and cartilage
- fibrosis
- Chronic infection
Bronchiectasis
Morphology: Gross
- Dilated of airway
- Saccular or cylindrical
- Thick wall
- Luminal exudate
- Grey, green or tan thick mucoid or caseous
Bronchiectasis
Functional Significance
- Increase airway resistance
- Due to turbulence and luminal obstruction
- Poor mucociliary clearance
- Aspiration of infective material to alveoli
Bronchiectasis
Sequelae
- Bronchiectasis is irreversible
- Progression of inflammation
- Continued bronchial damage
- Pneumonia
Bronchiolitis Obliterans
Definition
- Obstruction of the bronchiolar lumen by fibrous connective tissue
Atelectasis
Definition
- Collapse of the lung
*Normal lunch should be pink because it’s got a lot of air in it
Atelectasis
Classification
- Neonatal
- inadequate surfactant
- Acquired
- compressive
- obstructive
Atelectasis
Compressive
- Fluid, air, mass compresses lung or results in loss of negative pleural pressure
- Animals with well developed secondary lobules
Atelectasis
Pathophysiologic significance
- Segment of lung is underventilated
- Hypoxemia
- if widespread
Atelectasis
Sequelae
- Resolution of cause: Reinflation
- Alveolar edema
- Seondary bacterial pneumonia
- Fibrosis and irreversible collapse
Pulmonary Emphysema
Definition
Enlarged gas-filled space in lung
- Classification:
- Alveolar emphysema
- Interstitial emphysema
Collateral ventilation
equilization of pressure across lungs due to interalveolar pores (little defect in alveolar walls)
*animals with well developed secondary lobules are isolated
Alveolar Emphysema
Pathophysiologic Significance
- Decrease alveolar and capillary surface area
- Loss of radial support for airways: early closure
- Decrease elastic properties; increase compliance and residual lung capacity
- Loss of capillary area
- pulmonary hypertension and cor pulmonale
- leads to inc load on R. side of heart
- pulmonary hypertension and cor pulmonale
*Alveolar emphysema is irreversible
Interstitial Emphysema
Definition
- Excess gas in the pulmonary interstitial
- occurs in species with extensive interlobular septa
Interstitial Emphysema
Pathogenesis
- Forced expiration against obstructed airways
- Gas dissects into interstitial tissue
- Interlobular septa
- Perivascular areas
- Subpleural tissues
*Cattle with thoracic skin emphysema
Interstitial Emphysema
Pathophysiologic significance
Compression of lobules decreases ventilation
-restrictive lung disease
Interstitial Emphysema
Sequelae
- Resolution
- Progression
- mediastinum and subcutis
- Secondary infection of pockets
- Fibrosis and parenchymal loss
Pulmonary edema
Causes
-
Inc hydrostatic pressure
- associated with cardiac dz
- Inc vascular permeability
- Hypoalbuminemia
- Obstruction of lymphatics
- Inc Na
The most common cause of bronchiectasis is?
- A. Viral infection
- B. Chronic dust inhalation
- C. Chronic bacterial infection
- C. Chronic bacterial infection => neutraphils
Which of the following is reversible?
- A. Bronchiectasis
- B. Bronchiolitis obliterans
- C. Atelectasis
- D. Alveolar emphysema
- C. Atelectasis
- plural effusion
Pneumonia
Simple morphologic classification
- Bronchopneumonia
- Interstitial pneumonia
- Focal or multifocal pneumonia
- embolic
- Mixed pattern
- id: bronchointerstitial
- Modifiers
- Duration: acute, subacute, chronic
- Distribution: focal, multifocal, locally-extensive, diffuse
- Exudate: necrotizing, fibrinopurulent, granulomatous
Bronchopneumonia (95%) vs Interstitial pneumonia (5%)

Bronchopneumonia
Pathogenesis
- Initial deposition of causative agent in terminal bronchioles and alveoli
- often bacteria, foreign material
- aspiration
- often bacteria, foreign material
- Early damage is in proximal acinar areas with spread into surrounding alveolar parenchyma
Bronchopneumonia
Mrophology: Gross and microscopic
- Gross
- cranioventral
- may be intercurrent fibrinous pleuritis
- common in horses, cows, and sheep
- this may be what elicits most dramatic clinical signs
- may spread to have lobar distribution
- chronicity: fibrosis and lymphadenomegally
- fibrosis as pleural adhesions
- Microscopic
- Abudant exudate in alveoli including
- neutrophils
- fibrin
- necrotic debris (edema fluid)
- Lesions initially airway oriented
- Abudant exudate in alveoli including
Bronchopneumonia
Pathophysiologic significance
- Obstructive and restrictive pathophysiologic changes
- airway obstructed
- infiltration of walls and filling of alveoli => makes lungs stiffer
- exudate and alveolar wall thickening creastes diffuse barrier
- decreased diffuse capacity
- Pleuritis may contribute to restrictive dz
- decrease in tidal volume
Bronchopneumonia
Sequelae
- Resolution
- Death
- Septicemia
- Chronic bronchopneumonia with bronchiolitis obliterals and bronchiectasis
- +/- plueral adhesions
Interstitial pneumonia
Pathogenesis
- Primary injury to elements of the interalveolar septum
- epithelial
- endothelial
- Causes
- infectious
- toxic
- hypersensitivity
- Infectious agents
- virus
- protozoa
- some fungi
- rarely bacterial
- eg: associated with bacteremia
Interstitial penumonia
Morphology: Gross and microscopic
- Gross
- Often diffuse or locally extensive, firm, large, red, with muscle or liver consistency on cut surface
- Microscopic
- Early type 1 epithelial necrosis
- Subacute: type 2 epithelial hyperplasia, alveolar septal thickening, mononuclear cells
- Chronicity marked by fibrosis
Interstitial Pneumonia
Pathophysiologic significance
- Thickening and infiltration of alveolar walls marked by increased stiffness and decreased compliance
- restrictive dz
- Decreased diffusion capacity
- hypoxemia
Interstitial pneumonia
Sequelae
- Resolution
- Death
- Fibrosis of interalveolar septa and progressive restrictive lung disease
Pneumonia
Simple morphologic classification
- Bronchopneumonia
- Interstitial pneumonia
- Focal or multifocal pneumonia (embolic)
- Mixed pattern
- bronchointerstitial
- Modifiers
- Duration: acute, subacute, chronic
- Distribution: focal, multifocal, locally-extensive, diffuse
- Exudate: necrotizing, fibrinopurulent, granulomatous, etc
If the distribution of pneumonia is cranioventral, the most likely morphologic diagnosis would be:
- A. aspiration pneumonia
- B. fungal pneumonia
- C. viral pneumonia
- D. bronchopneumonia
- E. Interstitial pneumonia
- D. Bronchopneumonia
If it is bronchopneumonia, the most likely cause(s) is/are:
- A. Bacteria
- B. Virus
- C. Aspiration
- D. A and B
- E. A and C
- E. Bacteria and aspiration
*viruses do predispose the animal to secondary bacterial infections
If the pneumonia is diffuse, the least likely cause is:
- A. Virus
- B. Protozoa
- C. Toxins
- D. Aspiration
- E. Bacterial septicemia
- D. Aspiration
Acute Viral Pneumonia
Pathogenic Essentials
- Viruses replicate in respiratory airway and alveolar epithelial cells
- Virus induces inflammatory and immune response
- Inflammation in parenchyma is focused on interalveolar septa
- Viral replication is effectively halted before diffuse interstitial pneumonia develops
Acute Viral pneumonia
Morphologic features
- Virus-induced epithelial injury and inflammation
- Rhinitis
- Tracheitis/Bronchitis
- Bronchiolitis
- Patchy interstitial pneumonia
- spread contained by effective antiviral response
*Pattern of ‘c and d’ = bronchointerstitial pneumonia
- garbage can term….lol
Canine Adenovirus 2 infection
- Very effective vaccine exists
- Initially replicated in upper respiratory tract
- trachea
- bronchi
- When it goes into lung it hits bronchioles
- bronchiolitis
- replicates in airway eipthelium: non-ciliated cells and mucous cells
- Progression
-
patchy interstitial pneumonia (replicates in type 2 alveolar epithelial cells)
- more damage around airways, less damage deeper in lung
- 5-6 days after inoculation immune response stops replication
-
patchy interstitial pneumonia (replicates in type 2 alveolar epithelial cells)
- Lesions tend to be cranioventral
Chronic Viral Pneumonia
Pathogenic Essentials
- Often associated with viruses that replicate in macrophages and/or depress or escape antiviral immunologic defense mechanisms
- Virus spreads throghout the lung and induces diffuse interstitial pneumonia
- Examples:
- Lentiviruses (retroviruses)
- escape immune defenses
- Immunosuppressive examples
- Ovine progressive pneumonia
- Canine distemper virus
- Lentiviruses (retroviruses)
Bacterial Pneumonia
Patogenic essentials
(pneumonic pasteurellosis: mannheimia (Pasteurella) haemolytica
- Colonization of respiratory tract
- Depression of pulmonary defense mechanisms
- viruses
- stress
- dehydration
- particulates (crowding, indoors)
- Exponential growth of mannheimia haemolytica with leukotoxin production
- Damage to neutrophils, macrophages, release of endotoxin
- Leukotoxin and endotoxin-mediated tissue damage
- accentuated by neutrophil release of toxic molecules
Bacterial Pneumonia
Acute Lesions
- Bronchopneumonia
- Diffuse fibrinous pleuritis
- manheimia
- pasteurellas
- mycoplasmas
Bacterial pneumonia
chronic lesions
- Widespread fibrosis of pleura (white)
- restrictive pleuritis
- Nodular appearance possible from secondary infection
- pasturella multocida
- truperella pyogenes
Acute respiratory viral infections often induce pulmonary lesions including
- A. Bronchitis
- B. Bronchiolitis
- C. Patchy interstitial pneumonia
- D. Diffuse interstitial pneumonia
- E. A, B, and C
*influenza, parainfluenza, adenovirus
- E. Brochitis and Bronchiolitis (kennel cough), and patchy interstitial pneumonia
*
What mechanism accounts for some respiratory viruses being able to induce chronic pneumonia and diffuse interstitial pneumonia?
- A. They replicate in type 1 epithelial cells
- B. They replicate in type 2 epithelial cells
- C. They evade or suppress immunological defense mechanisms
- C. They evade or suppress immunological defense mechanisms
* Because it is diffuse they have to evade defense mechanisms
*Respiratory viruses being able to induce pneumonia is because of B . They replicate in type 2 epithelial cells
Bovine Toxic Interstitial Pneumonia
Pathogenetic Essentials (5)
- Ingestion of pneumotoxin
- L-tryptophane/3-methylindole
- moldy sweet otatoes (4-ipomeanol)
- Perilla mint (purple mint)
- stinkwood (ziera arborescens)
- Ruminal conversion and/or intestinal absorption
- Activation of pneumotoxin by pulmonary cytochrome P450 monooxygenase
- Covalent binding or free radical damage by metabolites and pulmonary cell death
- Pulmonary cells most susceptible to toxic injury
- nonciliated bronchiolar cells
- type 1 alveolar epithelial cells
- capillary endothelial cells
Think of toxic interstitial pneumonia if….
- cattle/horses that die and lungs show patterns of
- interstitial pneumonia
- bronchial necrosis
- no inflammatory/immune response
Toxic Interstitial Pneumonia
- Type 1 epithelial cells
- large surface area
- susceptible to damage
- incapable of division
- If Diffuse proliferation of Type 2 cells, indicates a interstitial pneumonia
- Diffusesness might mean hematogenous spread
Which of the following pulmonary injuries is most likely to induce the most severe irreversible lung and pleural damage?
- A. Viral infection
- B. Bacterial infection
- C. Dietary pneumotoxins
- B. Bacterial
- lots of neutraphils
- lots of fibrin that is corrected by fibrosis then adhesions
- persistent restrictive mechanism
Which of the following contain toxins activated by pulmonary cytochrome P450 monoxygenase to induce interstitial pneumonia in cattle and/or horses?
- A. Moldy sweet potatoes
- B. Mold damaged corn
- C. Purple mint (Perilla mint)
- D. A, B, and C
- E. A and C
- E. A and C Moldy sweet potatoes and Purple mint
Pulmonary Neoplasia
age of onset
Classification
- More common in dogs and cats than other spp
- dogs: 10-11 yo; cats: 12-13 yo
- Common simple classification
- benign epithelial tumors
- Adenoma
- Papilloma
- malignant epithelial tumors
- Adenocarcinoma
- Carcinoma
- Squamous cell carcinoma
- Adenosquamous carcinoma
- Bronchial gland carcinoma
- sarcoma (fibro, osteo…)
- benign epithelial tumors
*metastatic neoplasia is the most common form of neoplasia in the lung
Pulmonary Neoplasia
Gross Distribution
Biological behavior of carcinomas
- Gross distribution: most common in caudal lungs
- any lobe can be affected
- Biological behavior of carcinomas
- metastasize locally:
- thorax
- lung
- lymph node
- distant metastasis:
- lymph node
- kidney
- liver
- spleen
- bone
- brain
- nail bed in cats
- metastasize locally:
Histologic features of carcinomas
- obliteration of normal architecture
- replacement by papillary or acinar-like infiltrates of cells with high nuclear:cytoplasmic ratio
The most common form of pulmonary neoplasia is
- A. Adenoma
- B. Adenocarcinoma
- C. Fibrosarcoma
- D. Leiomyoma
- E. Metastatic
- E. Metastatic
Viral pneumonias in dogs
- Canine Distemper
- Canine Influenza
- Canine Adenovirus type 2
- Parainfluenza type 2 virus
- Canine respiratory coronavirus
- Canine herpesvirus 1
- more imp to younger dogs
*All will induce a patchy, interstitial pneumonia
*kennel cough CS
Canine distemper
Pathogenesis
- Respiratory/oropharyngeal inoculation
- Replication in oropharyngeal lymphoid tissue and viremia
- Replication in lymphocytes, epithelial cells, monocytes/macrophages cell lineages, nervous tissue cells
- Failure of cell/humoral/natural immunity leads to penetration of the blood-brain barrier and severe encephalomyelitis
*pancytopenic
Canine distemper
Respiratory lesions
- Rhinitis, pharyngitis, tracheitis, bronchitis, bronchiolitis
- Patchy to diffuse interstitial pneumonia or bronchointerstitial pneumonia
- may appear as bronchopneumonia if secondary bacterial infection
- Cytopathic effects
- intranuclear and intracytoplasmic inclusions in epithelial cells and macrophages (cytoplasmic inclusions predominate)
- syncytial cells
Canine Distemper
Non-Respiratory lesions
- Gastrointestinal (diarrhea)
- Lymphoid (lymph nodes, spleen, thymus)
- Dermatitis, Conjunctivitis
- Cystitis, other urinary tract lesions
- Teeth: enamel hypoplasia
- Nervous tissue; Eyes
Canine Distemper
- Diagnosis at Necropsy
- Submit tissue for histopath
- lung
- brain
- thymus
- lymph node
- spleen
- stomach
- urinary bladder
- PCR (tissues/swabs)
- respiratory panel PCR on swabs
- distemper
- coronavirus
- CAV2
- Parainfluenza
- H3N8/H3N2; H1N1
- Canine herpesvirus 1
- Bordetella bronchiseptica
- respiratory panel PCR on swabs
- Submit tissue for histopath
Canine Influenza Virus
Virus isolates
- H2N8 recognized in 2004 in Florida
- H3N2 emerged in 2007 in South Korea; 2015 in Chicago
- produces more severe clinical dz
- Both produce similar dz
Canine flu
Disease
- Most commonly seen in shelters, kennels, dog day care, etc
- H3N8 first seen in racing greyhound dogs
- Highly contagious
- Fever and persistent coughing in dogs
- +/- nasal d/c
- +/- pneumonia
- fatality (10%)
- often seen with secondary pneumonia
Canine flu postmortem
Respiratory and histo lesions
- Lymphocytic or suppurative rhinitis
- Erosive/hyperplastic tracheitis, bronchitis and bronchiolitis
- Tracheal/bronchial gland epithelial cell necrosis/hyperplasia with lymphocytes/neutraphils
- Patchy interstitial pneumonia (bronchointerstitial pneumonia)
- Suppurative bronchopneumonia with secondary bacterial pneumonia
- mild to severe
Morph dx

- Bronchopneumonia
- cranioventral
- firm
- red
- Probs culture out bacteria
Emerging viral respiratory agents
- Canine pneumovirus
- similar to PVM in rodents
- Canine bocavirus
- parvoviridae related to minute virus of canines
Mycotic Pneumonias in dogs
- Blastomycosis
- Histoplasmosis
- Coccidioidomycosis
- Pneumocystosis
- Cryptococcosis
Blastomyces dermatitidis
(Didn’t have time to cover in lecture)
- Granulomatous pneumonia and pyogranulomatous pneumonia
- mycelial and yeast forms in lesions
- yeast forms: 5-25 micrometer diameter
- doubly refractile, broad-based budding
- stains: PAS and GMS
Blastomyces dermatitidis
Lesions
(didn’t have time to cover in class)
- Extrapulmonary lesions
- skin, liver, spleen, lymph nodes, kidneys, eyes
- Lung lesions confused with disseminated carcinomas
- blastomycosis in young dogs: 2-5 yo
Coccidioides immitis
(didn’t have time to cover in class)
- Granulomatous pneumonia and pyogranulomatous pneumonia
- Spherules: 20-100 micrometer diameter with endospores
- Ruptured spherules: induce neutrophil infiltrates
- pyogranulomous lesions
- Extrapulmonary lesions
- lymph nodes
- spleen
- bone
Pneumocystis carinii
(didn’t have time to cover in class)
- Diffuse interstitial pneumonia
- unusual manifestation for fungal dz
- Associated with immunosuppresion
- Ribosomal RNA sequence: fungal
- most consistent with fungal (controversial)
- “trophozoites” (1-4 micrometers) attach to type 1 cells, induce damage
- Cysts (5-7 micrometers) in alveolar spaces
- are detectable by GMS and PAS
Cryptococcus neoformans
(didn’t have time to cover in class)
- More commonly induces encephalitis and nasal/sinus infections
- Pneumonia common if immunosuppression
- Induces granulomatous pneumonia
- Organisms 1-7 micrometers diameter with 1-30 micrometer diameter capsule
- PAS, GMS positive