Pleural Diseases in the Horse Flashcards
What is the definition of pleura?
Thin membrane of connective tissue plus a layer of mesothelial cells
What is parietal pleura?
Lining of the thoracic cavity
What is visceral pleura?
Covers the outer surface of the lungs and other thoracic structures
What is the Pleural cavity?
the space between the parietal and the
visceral pleura (right and left). Normally just a potential space
with a small volume of pleural fluid lubricating the surfaces
What is the mediastinum?
Central thoracic area between the two lungs and the two pleural cavities
What may the pleural space fill with potentially?
- Fluid (transudate, exudate)
- Blood
- Chyle
- Air
What disease is rare in horses?
Pleural disease with transudate
How might pleural disease with transudate arise?
- Increased venous pressure
- Congestive heart failure
- Decreased plasma colloidal pressure
- Hypoproteinaemia
What disease is extremely rare in horses?
Pleural disease with chyle
- generally follows blunt trauma
What is the composition of modified transudate?
mild increase in cells (5-20x109/L, mixed cell types, <90% neutrophils,
possibly exfoliated neoplastic cells), and mild increase in protein (20-30 g/L)
What two things are typical of thoracic neoplasia?
- Blockage of lymphatic drainage
- Inflammatory response to a neoplasm
Give three examples of pleural disease with modified transudate?
- lymphoma
- melanoma
- mesothelioma
What is the most common reason for pleural effusion?
Exudate- - moderate to marked increase in neutrophils (some
degenerate) and protein in pleural fluid
What four things result from bacterial infection
pneumonia (pleuropneumonia)
* penetrating thoracic trauma
* metastatic abscess (e.g. Strep equi equi, Rhodococcus equi)
* oesophageal rupture
What are the four steps of pleuropneumonia?
- Begins as a bacterial infection of the airways (septic bronchitis)
- Infection and inflammation spreads to the pulmonary parenchyma
- Infection and inflammation spreads to the visceral pleura
- Exudation into the pleural cavity
What is the main risk factor for pleuropneumonia?
Long distance transport/ head tied up= poor mucocilliary clearance
Name four risk factors for pleuropneumonia
- Head tied up = poor mucocilliary clearance
- Enclosed airspace= poor air hygeine
- Mixing with other horses= spread of pathogens
4.
What does pleuropneumonia ocassionally follow?
- severe and strenuous exercise (stress?)
- general anaesthesia (stress, tracheal intubation?)
- external wounds
- aspiration pneumonia (e.g. post-“choke”)
- oesophageal rupture
What are the clinical signs of pleuropneumonia?
often not a clinically obvious
diagnosis
* fever, dullness
* shallow and rapid breathing
pattern?
* chest pain (elbows
abducted, walks slowly,
grunting, may appear
“colicky”?)
* possibly a soft cough (N.B.
chest is painful)
Name 5 diagnostic tests for pleuropneumonia
- Clinical Picture
- Blood Sampling
- Endoscopy
- Ultrasonography
- Pleurocentesis
What does a pleuropneumonia endoscopy usually show?
Usually simply shows white-creamy-yellow
exudate
* >95% neutrophils
* Sometimes shows orange exudate or frank
bleeding
* Culture from trachea is more successful
than culture from the pleural fluid
* Often mixed oropharyngeal bacteria
* Streptococci
* Enterobacteriacea
* Anaerobes
* Klebsiella sp. especially
destructive and persistent
What does a pleuropneumonia ultrasonography usually show?
- Points of ultrasound penetration that represent pleural roughening and inflammation
- Larger areas of lung consolidation
- Pleural effusion
- Pleural fibrin
What is the medical therapy needed for pleuropneumonia?
- Antimicrobials
- NSAIDS
- Anti-fibrogenesis
- Fibrinolytics
Name three other causes of pleural exudate
- Penetrating trauma
- Aspiration following oesophageal obstruction (choke)
- Oesophageal rupture
