Respiratory pathology 2

Question 1

Give 2 examples of developmental abnormalities associated with the larynx and trachea

Answer 1

• Hypoplastic trachea (often in young brachycephalic dogs)

- Tracheal collapse (miniature and toy breeds affected)

Question 2

What are the consequences of a hypoplastic trachea?

Answer 2

• Don’t have enough airflow to support the body size
• Decreased tracheal lumen diameter causes highly increased resistance
• Dyspnoea (breathing difficulty)
• Exercise intollerence

Question 3

How does laryngeal paralysis differ in dogs and horses?

Answer 3

Horses - unilateral, primarily on the LHS

Dogs - bilateral

Question 4

What are some of the causes of laryngeal paralysis?

Answer 4

• idiopathic neuronal degeneration
• congenital abnormality
• toxins
• compression or irritation of the nerve (neoplasia, trauma, disease)

Question 5

What results from damage to the recurrent laryngeal nerve, how does this affect inspiration?

Answer 5

• Atrophy of cricoarytenoids muscles

- Failure of one or both of the arytenoid cartilages to abduct during inspiration

Question 6

Atrophy of the left cricoarytenoid muscle causes what disease in horses?

Answer 6

Equine laryngeal hemiplegia (roaring)

Question 7

Describe how Equine laryngeal hemiplegia (roaring) affects the airway

Answer 7

Flaccid left arytenoid cartilage and vocal cords are sucked into the airway causing a roaring noise

Question 8

How does laryngeal oedema occur?

Answer 8

Fluid exudate from blood vessels causes swelling of the larynx

Question 9

What are some of the causes of laryngeal oedema?

Answer 9

• Local trauma e.g. intubation
• Irritants
• Acute respiratory infections
• Allergic reactions

Question 10

What are the causes of laryngitis/tracheitis (inflammation)?

Answer 10

• infectious agents
• trauma
• irritants
• parasites

Question 11

What can be seen grossly on the tissue as signs of laryngitis/tracheitis?

Answer 11

• mucosal hyperaemia
• oedema
• ulceration
• serous or catarrhal exudate

Question 12

Laryngeal necrobacillosis has what affects on the body and how does it affect the animal?

Answer 12

• ulcerative necrosis of the larynx

- death due to toxaemia, asphyxiation and aspiration pneumonia

Question 13

Give examples of anatomical factors that render the bronchioles vunerable

Answer 13

• lack of supporting cartilage
• few cilia and no mucus
• clara cells are metabolically active and can produce reactive metabolites

Question 14

Give examples of causes of acute bronchitis and bronchiolitis

Answer 14

• infectious agents
• irritants
• allergens
• foreign bodies
• parasites e.g. Dictyocaulus viviparus

Question 15

Overall the acute inflammatory reaction is similar to the upper airways, but what can happen in addition to this in the bronchi/bronchioles?

Answer 15

Severe bronchiolitis can cause bronchiolitis obliterans

Question 16

Describe bronchiolitis obliterans and how it becomes obstructive

Answer 16

• Results in loss of epithelium and attachment of exudate to the basement membrane
• epithelium repairs around the exudate
• exudate is infiltrated by WBCs and fibroblasts (which lay down fibrous tissue and collagen) to form a polyp
• Polyp becomes covered in epithelium leaving a permanent obstructive lesion in the bronchiolar lumen

Question 17

What are the 3 possible causes of chronic bronchitis and bronchiolitis?

Answer 17

• Chronic or repeated infections
• Parasitic disease
• Allergic disease

Question 18

How does chronic bronchitis and bronchiolitis lead to an increase in mucus production?

Answer 18

• Bronchial goblet cell hyperplasia
• Bronchial gland hyperplasia
• Goblet cell metaplasia in bronchioles

Question 19

How does chronic bronchitis and bronchiolitis lead to thickening of the mucosa?

Answer 19

• Bronchial gland hyperplasia
• Epithelial hyperplasia and metaplasia
• Smooth muscle hyperplasia around airways
• Inflammatory cells and fibrosis

Question 20

What are the two main outcomes in the airways of chronic bronchitis and bronchiolitis?

Answer 20

• Increased mucus production

- Thickening of the mucosa

Question 21

How is partial / complete obstruction of airways clinically reflected?

Answer 21

• Difficulty breathing
• Cough
• Increased respiratory noise
• Collapse
• Reduced blood oxygenation

Question 22

What is bronchiectasis?

Answer 22

• Obstruction of the lumen by exudate – mucus stays in the airways
• Inflammatory cells release their lysosomal enzymes which cause damage to the bronchiole wall
• Necrosis of the bronchial wall causes permanent dilation of the bronchus

Question 23

Give 2 examples of conditions causing chronic bronchitis + bronchiolitis

Answer 23

• Cattle lungworm = Dictyocaulus viviparus

- Equine recurrent airway obstruction

Question 24

How does cattle lungworm cause chronic bronchitis and bronchiolitis?

Answer 24

• larval migration through the alveoli can cause acute pneumonia and blockage of the bronchioles with exudate
• Adult worms in the bronchi cause irritation, increased mucous production and thickened mucous

Question 25

How does Equine recurrent airway syndrome cause chronic bronchitis and bronchiolitis?

Answer 25

Asthma like condition, immune mediated hypersensitivity reaction (type III) to inhaled allergens in mouldy hay

Question 26

How are the bronchioles affected in equine recurrent airway obstruction?

Answer 26

• increase mucus
• mucosal thickening
• peribronchial fibrosis
• bronchospasm

Question 27

What are the clinical signs of equine recurrent airway obstruction?

Answer 27

• Cough
• Mucopurulent exudate
• Exercise intolerance
• Forceful expiration => abdominal muscle hypertrophy