Pathology

Question 1

What are the 4 primary defense mechanisms of the respiratory tract?

Answer 1

1. Particle deposition (air turbulence,warm, humid nasal turbinate air)
2. Mucociliary escalator
3. alveolar mø
4. inflammation and pulmonary immune response

Question 2

What is the number one cause of congestion/edema?

Answer 2

Increased capillary hydrostatic pressure

Question 3

What is the main reason why horses get sick?

Answer 3

Because of transportation and stress

Question 4

What is Hypostatic Congestion?

Answer 4

NO SIGNIFICANCE! Dead animal in prolonged lat recumbency -> gravity causes blood to go into side closest to ground -> post-mortem change

know its normal b/c lungs are still soft

Question 5

What are other causes of edema?

Answer 5

1. increased permeability
2. injury of epithelial cells (toxic gases, 100% O2, virus infection)
3. injury of endothelial cells (Virchow’s triad)
4. decreased plasma oncotic pressure (chronic nephritis, cirrhosis)
5. lymphatic obstruction (e.g., metastatic malignant melanoma in lung)

Question 6

What is an embolus and embolism?

Answer 6

Embolus: Any foreign body circulating in the blood or lymphatic

Embolism: an embolus gets stuck in a smaller caliber vessel

embolism more common than thrombosis

Question 7

What causes thrombus to form?

Answer 7

Parsites (e.g., heartworms), hypercoag. disorders, endothelial damage

Question 8

Why are renal infarcts much more common than lung infarcts?

Answer 8

One renal artery versus a dual artery system in the lungs

need ~60% of pulmonary vasculature to be affected to have clinical signs (there are millions of vessels in the lungs!)

Question 9

What is a consequence of pulmonary thrombi or emboli?

Answer 9

Pulmonary infarct (super rare)

Question 10

What are two abnnormalities of inflation in the lungs?

Answer 10

Atelectasis and Emphysema

Question 11

What is the defintion and causes of Atelectasis?

Answer 11

Atelectasis: too little air in the lung/incomplete expansion of the lung
- Congenital: fetal
- Acquired: Obstructive v. Compressive

Question 12

What are cases of Congenital-caused Atelectasis?

Answer 12

Fetal: stillborne
Neonatal and dystocia: aspirate colostrum, hypoxic conditions

Question 13

What is collateral ventilation and what species lack it?

Answer 13

Ventilation of alveoli via pathways that bypass normal airways; beneficial in disease states of obstructed or restricted airways as it serves as a back-up system. Bovine, swine and marine mammals lack this.

Question 14

What is Obstructive - Acquired Atelectasis?

Answer 14

Inflammatory exudates obstructing bronchioles (or parasites, neoplasia)

Question 15

What is Compressive - Acquired Atelectasis?

Answer 15

blood, pus or air in the lungs that causes the pleural cavity to lose its negative pressure -> lungs collapse

hemothorax, chylothorax, pneumothorax

Question 16

Interstitial Emphysema

Answer 16

• Most common type in ruminants
• forced expiration (pneumonia, agonal breaths) causes bronchiolar collapse -> alveolar rupture -> air leaks into interlobular septa
• Remember: bovines have NO collateral ventilation! The trapped air in the distal alveoli is what causes the alveoli to rupture

Causes of forced expiration: pneumonia, agonal breathing

Emphysema: tissue expansion by air or gas

Question 17

Where do most primary lung tumors orginate from?

Answer 17

From the alveolar and bronchiloar epithelium, and are frequently located in the pulmonary hilum

Question 18

What is Feline lung-digit syndrome?

Answer 18

where lung cancer selectively spreads or metastasizes to the nailbeds and toes, usually occurring before signs of respiratory distress/pulmonary disease

The observation of lameness or progressive, lytic lesions of the digits should prompt veterinarians to work up for a primary lung mass, especially in high-risk cats. Up to 88% of carcinoma in the feline digit may be metastatic from a pulmonary lesion.

Question 19

What is the general rule of tumor malignancy potential in dogs and cats?

Answer 19

Dogs: tumors > 3cm in diameter
Cats: tumors >1cm in diameter
= potentially malignant

most malignant tumors originate from benign proliferations!

Question 20

Answer 20

Question 21

Answer 21

fibrin = damage to vasculature = damage to coag cascade

Question 22

Answer 22

Question 23

Answer 23

Common sequela = pulmonary abscess

Question 24

Answer 24

Granuloma: a focal cluster of macrophages/inflammatory cells that form in response to infection.

NO PUS!

Question 25

What is **bronchlectasis**

Answer 25

Rupture and dilation of bronchial wall due to enzymatic effect of neutrophils and macrophages; is an irreversible lesion! occurs in cows with mycoplasma bovis infection

Question 26

Etiology of suppurative vs fibrinous bronchopneumonia

Answer 26

Suppurative bronchopneumonia: mycoplasma spp. Fibrinous bronchopneumonia: highly pathogenic bacteria (Mannheimia, Actinobacillus)

Question 27

Pathogenesis of fibrinous inflammation in bronchopneumonia

Answer 27

severe lung injury -> fibrinogen leaks out of vessels & is converted into fibrin via thrombin (clotting enzyme) -> *fibrin deposits in the pulmonary tissue*

Question 28

Distributiom of aspiration pneumonia

Answer 28

cranioventral *unilateral!*

Question 29

texture of interstitial pneumonia

Answer 29

elastic- alveolar walls become inflammed/thickened

Question 30

Answer 30

**embolism pneumonia** abscesses all over the lung = origin is not the lungs

Question 31

Sequel to embolic pneumonia

Answer 31

Pulmonary abscesses

Question 32

Answer 32

Granulomatous pneumonia in foal with *Rhodococcus equi* ## Footnote Rhodococcus equi is a bacterium that lives in the soil and can cause pneumonia in young (1 to 6 months old) foals. Infection progresses slowly and foals often do not begin to show clinical signs until the disease has become severe. R. equi can infect immunocompromised humans and cause lung infections. Many foals infected with R. equi recover, but those that are severely affected may not survive. Good foal management, regular screening, and early detection are the best approaches to prevent R. equi infection.

Question 33

Answer 33

Verminous pneumonia (small ruminants) -- by parasites // lung worms | Protostrongylus, Neostrongylus