Respiratory Pathology - lecture 2 Flashcards
what is atelectasis?
incomplete distension/inflation/expansion of alveoli
can affect whole lung, one lobe or a few lobules
what do atelectatic lungs look like?
sunken and darker in colour than normal lung, since alveolar walls are closer together
what are the 2 forms of atelectasis?
congenital and acquired
how does congenital atelectasis occur?
lungs aren’t inflated with air at birth
Happens because:
* aspiration of amniotic fluid, meconium or squamous epithelial cells ( = causing obstruction)
* surfactant problem –> alveolar septa stuck together
how does acquired atelectasis occur?
collapse of lung after inflation has happened
** common in animals**
what are the 2 types of acquired atelectasis?
- compressive = lungs compressed by something outside lungs but within thoracic cavity
- obstructive = something blocked an airway, preventing airflow –> alveolar collapse
what can cause compressive atelectasis?
- space occupying thoracic masses (ex. tumor, abscess)
- transferred pressure from outside lung, like in bloat, or thoracic effusions (ex. hydrothorax/fluid, hemothorax/blood, chylothorax/chyle, pyothorax/pis, pneumothorax/air)
what can cause obstructive atelectasis?
- narrow airway lumen
- edema or inflammation of airway mucosa
- obstruction by mucus, exudate, parasites (ex. lungworms) or aspirated material
what is emphysema? where can it happen?
over-distension/inflation and rupture of alveolar walls, forming air bubbles in the lung tissue/parenchyma
can happen in lung (alveolar emphysema), lung connective tissue (interstitial emphysema)
in context of emphysema, what are big, confluent bubbles called?
bullae
there are two types of emphysema: primary and secondary. which one occurs in animals?
secondary emphysema, usually as a consequence of a predisposed condition
how does secondary emphysema occur in animals?
- obstruction of airway (where air gets into alveoli but can’t get out … POP! goes the alveoli)
- agonal change at death (final gasp of animals against closed airways)
what does crepitus mean?
crackly feeling lungs due to accumulation of air bubbles
what are 5 examples of non-infectious lung diseases involving circulatory disturbances?
- congestion
- hemorrhage
- edema
- ARDS
- embolism
define pulmonary congestion
accumulation of blood and fluid in the lungs
what’s the difference between pulmonary congestion and hyperemia?
hyperemia = acute, active process of increased blood in organ
congestion = passive process, usually caused by heart failure
what types of lung hemorrhage can you have?
- gradual
- spectacular = sudden hemoptysis and death
- not real!! post mortem artifact
what would you notice in cases of gradual lung hemorrhage?
endothelial damage or clotting problems
ex. DIC, vasculitis, septicemia, coagulopathies
define pulmonary edema
accumulation of fluid in the pulmonary interstitium and alveoli
is it normal for fluid to leak into the alveolar interstitium from the capillaries?
yes - fluid is removed by lymph system or eaten by intra-alveolar macrophages
what are the two main categories of pulmonary edema?
- cardiogenic or hydrostatic edema
- permeability or inflammation related edema
what leads to cardiogenic edema?
- increased hydrostatic pressure (CHF)
- increased blood volume (iatrogranic or congestion)
- hypoproteinemia
- reduced lymphatic drainage (due to blockage to lymph vessels)
what leads to permeability edema?
- general lung inflammation or damage to pneumocytes lining alveoli –> increased vasc permeability
what MAJOR clue do you find in post-mortem that indicates pulm edema was likely the cause of death?
froth in the trachea and it’s gotta be extensive froth (because mild lung edema often happens at time of death regardless of cause)
what are other lesions in post-mortem that points to pulm edema?
- lungs don’t collapse when chest is opened
- prominent interlobular septa
- lungs are darker, wet and heavier than normal
what is ARDS? can you recognize it in post-mortem?
acute respiratory distress syndrome or “shock lung”
this is clinical diagnosis, no post-mortem lesion
how can pulmonary embolism cause respiratory disease?
the lung has a huge capillary bed so it is a sticky spot for emboli to lodge
what type of emboli can cause pulm embolism?
- thromboemboli (not common, since usually broken down by fibrinolysis)
- septic/bacterial emboli (embolic pneumonia or pulm abscess)
- fat emboli (from bone fractures, more human thing)
- tumor emboli (common)
is pulmonary neoplasia common in domestic animals?
no, although metastatic lung neoplasia is more common than primary lung neoplasia
what is hypertrophic osteopathy?
intrathoracic masses can induce periosteal proliferation in distal limb bones
