General Pathology Of The Respiratory Tract Flashcards
What are the types of atelectasis?
Primary and Secondary
What is primary atelectasis?
Failure of the lung tissue to expand at birth
What is secondary atelectasis?
Collapse of lung tissue which was previously expanded
What is emphysema ?
Excessive air within the lungs
What is a sign of sever emphysema?
Lungs fail to deflate and their are imprints of the ribs on the pleural surfaces
What are the types of primary atelectasis?
Total - all dark red
Partial - some salmon pink bits = inflated
When might you see partial primary atelectasis?
If the neonate has taken a few breaths then died ~10 mins after birth
What does atelectasis look like on histology?
Dense lung tissue - no air spaces
What can cause secondary atelectasis?
Compression
Obstruction
What compressive conditions can cause atelectasis?
Haemothorax
Hydrothorax
Pneumothorax
Neoplasm
Abscess etc.
Prolonged recumbency
Prolonged abdominal distension in Large animals — BLOAT
What obstructive conditions can cause atelectasis?
Foreign Body
Neoplasm
Thick secretions
How does obstruction cause atelectasis?
Air diffuses out across the alveolar wall but is not replaced
Wall collapses
What neoplastic condition could cause atelectasis?
Mediastinal lymphoma
Why is atelectasis secondary to obstruction less common in small animals?
Better collateral air supply
What is emphysema?
Excessive air in the lungs
What are the types of emphysema?
Alveolar
Interstitial
Compensatory
What is alveolar emphysema?
What is it typically caused by?
Permanent abnormal enlargement of airspaces distal to terminal bronchioles
Anything that causes inflammation and neutrophils
NEUTROPHIL ELASTASE
(RAO/severe equine asthma)
What is interstitial emphysema?
Septal lymphatic dilated with air secondary to FORCED EXPIRATION
Give an example of a condition that causes interstitial emphysema
Pneumonia in cattle
What can cause compensatory emphysema?
Areas of consolidation/partial atelectasis
What is severe equine asthma usually caused by?
Allergies to fungal spores in hay
What are the main types of pigmentation seen in the lungs?
Melanosis - melanin in alveolar walls
Anthracosis - carbon in alveolar macrophages
Describe the gross difference between melanosis and anthracosis
Melanosis - ‘splodges’
Anthracosis - ‘ sprinkled pepper’
What is the difference between hyperaemia and congestion
Hyperaemia - erythema - increased arterial blood IN
= exercise, inflammation
Congestion - cyanosis - decreased venous blood OUT
= hypoxia - local obstruction, congestive heart failure
What is cranioventral hyperaemia associated with?
Aspiration pneumonia
What post mortem change is associated with dependent congestion of the lungs?
Hypostatic congestion (livor mortis)
Describe the possible distributions of hyperaemia
Localised or diffuse
What would diffuse congestion of the lungs indicate?
Cardiac failure
When would you expect to see terminal pulmonary congestion?
Animals euthanised with barbituates
How does pulmonary oedema compromise ventilation?
Alveoli flooded by fluid
Mixes with surfactant to form foam
What physiological features resist pulmonary oedema?
Tight junctions between alveolar epithelium and capillary endothelium
Intra-alveolar pressure greater than interstitial pressure
Lymphatic drainage
What can cause pulmonary oedema?
Cardiogenic - LCHF
Neurogenic - sympathetic stimulation as a result of acute brain damage
Excessive IVFT
Damage to endothelium or epithelium
- toxic substances - smoke, paraquat (banned UK), 3-methyl indole, endotoxins
- acute inflammation
What does oedema fluid look like on histology?
Pale pink when stained with H&E
What is the triad of thrombosis?
Endothelial injury
Hypercoagulability
Abnormal blood flow
What is thrombosis?
Obstruction of vessels by coagulated blood components during life
Define embolism
Detachment of thrombi (or bacteria, tumours etc) which become lodged in small vessels
What is infarction
Death of tissue due to an interruption in its blood supply
What can cause jugular thrombosis
Iatrogenic - post catheterisation
What causes bovine malignant catarrhal fever?
Herpesvirus
How can you describe a pneumonia ?
Based on:
- distribution of changes in lungs
- type of inflammatory response
What are the main types of pneumonia?
Bronchopneumonia - fibrinous or suppurative
Interstitial pneumonia
Embolic pneumonia
Granulomatous pneumonia
how does an animal get bronchopneumonia?
Bacterial infection via airway
how does interstitial pneumonia occur?
Haematogenous infection - viruses or toxins
How does embolic pneumonia occur?
Through the blood - thrombi or bacterial emboli
How would an animal get granulomatous pneumonia?
Fungal or mycobacterium
Describe the typical distribution of bronchopneumonia
Cranioventral
How could bronchopneumonia deteriorate?
Abscessation
Pleuritis - with adhesions
DEATH - hypoxia and toxaemia
What would occur if bronchopneumonia persists?
BRONCHIECTASIS + fibrosis
What is bronchiectasis?
Permanent dilation of some bronchi due to irreversible damage to bronchial wall
What animals is bronchiectasis seen in as a consequence of chronic bronchitis or bronchopneumonia?
COWS (sheep, goats, pigs)
What is the common appearance of bronchopneumonia in cats and dogs?
Why?
LOBAR
Lack complete lobulation and septation
Can therefore easily spread throughout whole lobe
What causes a lobar pneumonia?
Highly toxic bacteria e.g. Pasteurella
Aspiration
What can cause bronchi-interstitial pneumonia?
Inhaled mycoplasma and some virus’s
Describe the histology of broncho-interstitial pneumonia
Cuffing of airways by lymphocytes
Interstitial lymphocytic proliferation
What is the importance of bronchi-interstitial pneumonia?
economic - reduced growth rates, predisposition to secondary infection
Describe the histological appearance of interstitial pneumonia
Inflammatory cells in interstitium
DIFFUSE distribution
What can cause an acute interstitial pneumonia?
Infections e.g. DISTEMPER Inhaled chemicals e.g. smoke Ingested toxins e.g. paraquat or tryptophan Systemic conditions e.g. uraemia Hypersensitivity reactions e.g. lungworm
What can cause chronic interstitial pneumonia?
Infections - Jaagsietke (retrovirus) in sheep
Inhaled dust - coal dust or silica
Hypersensitivity reactions - farmer’s lung
What is fog fever?
What is the causative agent?
Acute bovine pulmonary oedema and emphysema
TRYPTOPHAN
When is fog fever seen
When adult cattle moved to lush pasture in autumn
What is the pathogenesis of fog fever?
Excess tryptophan in autumn grass is metabolised in the rumen to 3-methyl idole
Toxic to type 1 pneumocytes
What can you get embolic pneumonia secondary to?
Endocarditis
Hepatic abscessation
Phlebitis
What is embolic pneumonia?
Pulmonary abscesses resulting from septic emboli in pulmonary vessels
How could you tell if mycobacteria were present in a sample?
Stain: Z-N
Acid fast will stain red
How could you stain for fungi?
PAS or silver stains
What is the predominant cell type in granulomatous pneumonia?
Neutrophils
What are polyps?
Hyperplastic tissue
Often pedunculated
Secondary to chronic inflammation e.g. in cats post cat flu - feline calicivirus
What are most common tumours which metastasise to the kings?
Mammary tumours
Thyroid carcinoma
Haemangiosarcomas
Osteosarcoma
What primary tumour tends to occur in the lungs?
Invasive carcinomas
Occur in hilar region before spreading within the lung
What are the malignant tumours which occur in the nasal and paranasal sinuses?
Carcinomas or sarcomas
