resp notes Q and A

Question 1

List the 3 most likely mechanisms of edema in the lung, and a likely specific cause for each.

Answer 1

1. Increased hydrostatic/venous pressure, e.g. left heart failure.
2. Reduced oncotic pressure, e.g. glomerular disease.
3. Increased vascular permeability, e.g. bronchopneumonia or acute interstitial lung injury.
4. Damage to type I pneumocytes, such as viral infection.
5. (Lymphatic obstruction)

Question 2

When you find a grossly visible thrombus in a large pulmonary artery, what are your considerations with respect to finding the cause?

Answer 2

This is likely an embolism, whereas in situ thrombi are usually (but not always) microscopic. Look for sources of embolism: heart valves, jugular vein, liver/caudal vena cava, and elsewhere. Consider whether the thrombi are extensive enough to obstruct blood flow.

Question 3

Explain how bronchiolar obstruction and pneumothorax can each cause atelectasis

Answer 3

Bronchiolar obstruction prevents ventilation of the alveoli. Once the trapped gas is absorbed, the alveoli collapse and cannot be re-filled.
Pneumothorax dissociates the lung from the rib cage. With air in the pleura, we can’t generate negative intrapleural pressure, which is necessary to inflate the lung.

Question 4

What is the clinical importance of distinguishing emphysema from air trapping in the alveolus?

Answer 4

Emphysema is a permanent change. Air trapping will return to normal, if the airway obstruction can be resolved.

Question 5

List 2 reasons for increased prominence of interlobular septa.

Answer 5

Fluid: interlobular edema.
Air bubbles: interlobular emphysema.

Question 6

List 2 substantially different ways that lung tumours can cause cough.

Answer 6

• Impinge on and irritate a large bronchus.
• Fluid leakage from the tumour resulting in pulmonary edema.

Question 7

List 2 ways to differentiate, at the time of necropsy, primary from metastatic neoplasia of the lung.

Answer 7

1. Primary: 1 or a few large masses, ± multiple metastases. Metastatic: multiple similarly sized masses.
2. Evidence of a primary tumour in another organ.
3. Histopathology can be helpful, but don’t neglect the importance of the above gross findings!

Question 8

List 2 ways that a (primary) pulmonary carcinoma could cause distal limb lesions.

Answer 8

1. Metastasis causing a focal mass in skeletal muscle or bone of the limb. This is seen in cats with pulmonary carcinoma.
2. Hypertrophic osteopathy, causing diffuse thickening of the periosteum.

Question 9

Is visual appearance or texture more reliable for gross assessment of lung?

Answer 9

Both are necessary, but trust your palpation skills. The visual appearance can be deceiving.

Question 10

In a dog with aspiration pneumonia, what predisposing lesions might you observe elsewhere in the body?

Answer 10

Lesions in other organs that predispose to aspiration would include megaesophagus, persistent right aortic arch, cleft palate, thymoma (causing myasthenia gravis), enteritis (parvovirus, inflammatory bowel disease, brain lesions, or a surgical incision associated with recent anesthesia.

Question 11

In a puppy with parvoviral enteritis, how would you distinguish whether bacterial infection of the lung was a consequence of vomiting or of reduced barrier function of the intestinal mucosa?

Answer 11

Vomiting would induce aspiration pneumonia, which would usually cause a localized cranioventral lesion of bronchopneumonia. Reduced mucosal barrier function would lead to sepsis, and the resulting lung lesions would be diffuse throughout the lung (interstitial pattern).

Question 12

Necropsy of a dog reveals consolidation and reddening of the right middle lung lobe, reddening but normal texture of the remainder of the lung, and isolation of Enterobacter sp., E. coli , and Citrobacter sp. Indicate the expected pathogenesis of the disease in this dog.

Answer 12

The presence of a localized lung lesion and a mixed culture of enteric bacteria suggests aspiration pneumonia.

Question 13

What bacterial pathogen is an important primary cause of bronchopneumonia in both dogs and cats?

Answer 13

Bordetella bronchiseptica.

Question 14

What are the three most important bacteria causing bronchopneumonia in cattle?

Answer 14

• Mannheimia haemolytica (and the related pathogen Bibersteinia trehalosi)
• Histophilus somni
• Pasteurella multocida
• Mycoplasma bovis

Question 15

Embolic pneumonia
- cause
- route of exposure
- gross distribution of lesions
- key histologic feature

Answer 15

• cause: baceria, fungi
• route of exposure: Hematogenous
• gross distribution of lesions: Generalized multifocal
• key histologic feature: Multiple random foci of inflammation

Question 16

bronchopneumonia
- cause
- route of exposure
- gross distribution of lesions
- key histologic feature

Answer 16

• cause: bacteria
• route of exposure: airway
• gross distribution of lesions: Cranioventral
• key histologic feature: Inflammatory exudates fill bronchiolar and alveolar lumens

Question 17

interstitial lung disease
- cause
- route of exposure
- gross distribution of lesions
- key histologic feature

Answer 17

• cause: Virus, sepsis, toxins, idiopathic
• route of exposure: Usually hematogenous
• gross distribution of lesions: Generalized, diffuse (or sometimes, lobular)
• key histologic feature: Hyaline membranes, type II pneumocyte proliferation, interstitial fibrosis

Question 18

airway disease
- cause
- route of exposure
- gross distribution of lesions
- key histologic feature

Answer 18

• cause: Viruses, bacteria, hypersensitivity
• route of exposure: Usually airway
• gross distribution of lesions: Absent or inconsistent
• key histologic feature: Necrosis of airway epithelial cells, or leukocyte infiltration targeting airways

Question 19

List the two most important viral respiratory infections of cattle and of cats.

Answer 19

Cattle: Bovine herpesvirus-1 (IBR virus), bovine respiratory syncytial virus.
> BVDV predisposes to bacterial pneumonia but does not cause primary viral respiratory disease.
> Other viruses include coronavirus and parainfluenza virus.
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Cats: Feline herpesvirus, feline calicivirus.

Question 20

List three mechanisms of airway obstruction in a pig with influenza.

Answer 20

1. Bronchoconstriction.
2. Edema thickening the airway wall due to inflammation.
3. Necrotic epithelial cells and leukocytes partially fill the airway lumen.

Question 21

What is the difference between bronchiectasis and bronchiolitis obliterans, with respect to morphology and cause?

Answer 21

• Bronchiectasis: permanent dilation of bronchi, caused by bacterial infection that results in pooling of exudates that obstructs and degrades the bronchial wall.
• Bronchiolitis obliterans: fibrous polyp filling the lumen of a bronchiole, the result of prior viral infection.

Question 22

Give one example of a pneumoconiosis.

Answer 22

Pneumoconioses are chronic interstitial lung diseases caused by inhalation of inorganic dusts. Examples include asbestos, silica, coal dust.

Question 23

What are the two main features of chronic interstitial lung disease?

Answer 23

1. Proliferation of type II pneumocytes
2. Fibrosis of alveolar septa