Respiratory inflammatory conditions Flashcards
Where is the primary site of injury for interstitial pneumonia?
Alveolar epithelium and capillary endothelium
What are the causes of interstitial pneumonia?
viruses, bacteria, protozoa, helminths, irritants, allergy and toxins
What are the two route of entry for interstitial pneumonia?
- inhalation
- haematogenous
How is interstitial pneumonia usually distributed in the lungs?
Diffuse
How would a lung with interstitial pneumonia appear grossly?
- heavy, rubbery, elastic texture
- red, grey mottled surface
- lack of visible exudate
- lungs fail to collapse on opening thorax
- Costal impression on pleural surface – where the ribs would have been when the lungs over expanded
What are the 3 phases of the acute response for interstitial pneumonia?
- Injury to type 1 pneumocytes or capillary endothelium
- Exudative response
- Proliferative phase
What occurs in the exudative response?
- Expansion of the interstitial tissue: oedema and inflammatory exudate
- Leakage of fluid and plasma proteins into the alveolar space
- May see hyaline membrane formation
What is the hyaline membrane?
A high protein density fluid made up of plasma proteins and surfactant which coats the alveolar spaces
What cells would be found in interstitial tissue?
Macrophages
Fibroblasts
Blood vessels
What occurs in the proliferative phase of interstitial pneumonia?
- Macrophage population expands, these phagocytose and remove the exudate
- Type II pneumocytes proliferate to replace lost type I cells
What are the functional consequences of acute interstitial pneumonia?
Disruption of alveolar walls
Oedema and exudate
= Hypoxia
How does acute interstitial pneumonia resolve?
- alveolar macrophages remove alveolar fluid and cells
- type II pneumocytes differentiate into type I
Give examples of causes of acute interstitial pneumonia
- Viruses e.g. distemper
- Migrating parasites
- Type III hypersensitivity reaction
- Toxins e.g. tryptophan
- Inhaled smoke
Give examples of causes of chronic interstitial pneumonia
- Infections e.g. Ovine lentivirus
- Hypersensitivity reaction
- Toxins
- Irritants
If interstitial pneumonia injury persists which 4 chronic changes occur?
- interstitial fibrosis
- chronic inflammatory cells
- persistence of type II pneumocytes
- smooth muscle hyperplasia around bronchioles
Which cells are present in chronic interstitial pneumonia?
Fibroblasts
Lymphocytes
Plasma cells
Macrophages
Which cells are present in acute interstitial pneumonia?
Proliferative type II cells
Macrophages
Exudate
What are the functional consequences of chronic interstitial pneumonia?
- thickened alveolar walls, which decreases lung compliance
- Increased respiratory effort
Which agents produce lesions that have features of both bronchopneumonia + interstitial pneumonia? (bronchointerstitial pneumonia)
Pneumotropic viruses
What are the consequences of thickened alveolar walls in chronic interstitial pneumonia?
- Reduced airspaces
- Impaired diffusion
- Reduced gas exchange
= hypoxia
= pulmonary hypertension
What is the route of entry and distribution of embolic pneumonia?
ROE = Haematogenous Distribution = random disseminated foci
What are the 3 common causes of embolic pneumonia?
- Hepatic abscesses
- Right heart valve endocarditis
- Joint/naval infections
What follows on sequalae to embolic pneumonia?
- Formation of abscesses
- Fibrosis and resolution
- Chronic pneumonia
- Rupture => pyothorax
Granulomatous inflammation is dominated by which 2 cells?
Macrophages and multinucleated giant cells
Which types of agents cause Granulomatous inflammation ?
- Ones that persist in tissues
- Induce chronic inflammation
What are the routes of entry and distribution of Granulomatous inflammation?
ROE = inhalation and haematogenous Distribution = variable, nodular foci
How do multinucleated giant cells form?
Fusion of macrophages in an attempt to phagocytose an agent more effectively
Give some examples of causes of Granulomatous inflammation
- Bacteria: Mycobacteria e.g. TB
- Parasites: migrating lungworm or heartworm
- Viruses: Feline infectious peritonitis
- Fungi
- Foreign bodies
What kind of exudate will be seen grossly in Granulomatous inflammation?
Caseous = cheese like
Bacteria causing Granulomatous inflammation will stain what colour with Ziehl-Neelson?
Purple
Gram +ve
Give examples of primary lung tumours (these are rare)
- Bronchioalveolar squamous cell carcinoma
- Papillary adenocarcinoma
How does neoplasia spread in/around the lung?
By not only metastasis but also locally within the lung through spread along the airways
- spread by friable tumour fragments in the airflow along bronchi and bronchioles
What is the favourable environment for pulmonary adenomatosis?
Housing sheep intensively overwinter - ovine pulmonary carcinoma
How is pulmonary adenomatosis induced?
Retroviral induced neoplasia - aerosol infection
How do the cells of pulmonary adenomatosis appear?
Predominantly cuboidal or columnar cells resembling type II pneumocytes.
How do the lungs of a sheep with pulmonary adenomatosis appear grossly?
- Lungs are heavy, with small grey to white nodules
- Copious amount of mucoid fluid
Why is metastatic spread to the lungs causing secondary neoplasia very common?
The lungs have a good blood supply and a fine capillary network
Give 3 examples of tumours that can be deposited in the lung
- Mammary tumours
- Osteosarcoma
- Haemangiosarcoma
Describe the pleural cavity and its role in the body
- Surround the lungs which are under partial pressure
- When the ribs expand outwards, the pressure is reduced and the lungs are drawn outwards
What is a pneumothorax?
The partial pressure in the pleural cavity has been dispersed, so the pleural pressure is the same as outside and the lungs collapse
How would a radiograph of a pneumothorax appear?
A lateral chest radiograph shows the lung size to be greatly reduced
What are some causes of a pneumothorax?
- Spontaneous rupture of abscess, emphysematous bulla
- Traumatic rupture or perforation of lung or trachea
- Penetrating injury of the thoracic wall
Pleural effusions all inhibit?
Lung expansion
What is a hydrothorax?
Oedema/transudate (low protein density fluid) in the pleural space
What are the causes of a hydrothorax?
- heart failure
- hypoproteinaemia
- intrathoracic tumours
What is a haemothorax?
Blood in the pleural space
What are the causes of a haemothorax?
- trauma and rupture of blood vessels
- erosion of blood vessels by tumours
- clotting disorders
What is a chylothorax?
Lymph in the pleural space
What are the causes of a chylothorax?
- traumatic rupture or neoplastic erosion of the thoracic duct wall
- heart disease
- congenital abnormality to the thoracic duct
What is a pyothorax?
Pus in the pleural space
What are the causes of a pyothorax?
Penetrating injury
Lung abscess rupture
What is the name given to inflammation of the pleural cavity/
Pleuritis
What are the causes of pleuritis?
- pneumonia
- bacteria
- pyothorax
- FIP virus
