Pleural Cavity Diseases Flashcards
What is the function of pleural fluid? How is it formed?
lubricated the lungs and allows the diffusion of substances, like electrolytes
when plasma exits from capillary beds in the tissue and enters the interstitial space
Where is pleural fluid formed and absorbed?
parietal surface
visceral surface
What is pleural effusion? What are the 4 mechanisms of fluid accumulation?
accumulation of excessive amounts of fluid within the pleural space from excess fluid production and/or decreased lymphatic absorption
- decreased oncotic pressure - hypoalbuminemia
- increased hydrostatic pressure - CHF
- increased capillary membrane permeability - inflammation due to FIP, neoplasia, pyothorax, or vasculitis
- lymphatic malfunction - obstruction, lymphangiectasia
How does pleural effusion cause clinical signs? What signs are the most common?
interferes with normal lung expansion
- restrictive breathing pattern (rapid, shallow, orthopnea, open mouth)
- dyspnea, cyanosis
- increased respiratory effort
- exercise intolerance
- pyrexia, anorexia, lethargy
What is the normal pressure of the pleural cavity? How does effusion affect this?
negative pressure, which works with surfactant to keep the lungs inflated
as pleural fluid accumulates, there is a gradual collapse of the lung parenchyma and an increase in intrathoracic pressure
Usually, once pleural effusion is removed, lungs refill. What is an exception?
when fibrin and scarring forms around lung edges from chronic inflammation and prevent re-expansion of lung tissue
What is commonly heard on auscultation in patients with pleural effusion? What signs should be looked for? What should especially be done on physical exams of cats?
muffled heart and ventral lung sounds, with increased lung sounds dorsally —> fluid accumulates ventrally, air remains dorsal
signs of CHF and neoplasia
compression of the anterior thorax to investigate possible mediastinal masses (which cause effusion)
How do lungs look on thoracic radiographs with pleural effusion?
outlined due to the presence of fluid between them and the body wall
What is the recommended immediate treatment for patients in distress with suspected pleural effusion?
thoracocentesis (treatment/diagnostic) before radiographs
- especially in cats
What is the recommended area for thoracocentesis? What equipment is commonly used?
between 7th and 8th ribs caudal to the costochondral junction
butterfly with 3-way stopcock (butterflies can take a while, but they prevent going too far in)
What is the difference in thoracocentesis technique in smaller and larger patients?
SMALL = oblique angle
LARGE = horizontal
(advance the needle slightly ventrally)
What should be done after turning the stopcock to perform thoracocentesis?
GENTLE SUCTION - no more than 2 mLs of negative pressure
(extension tubing can be used to allow independent movement of syringe)
After all of the fluid is attained from thoracocentesis what should be done?
- submit fluid for analysis
- take post-procedure radiographs or US
What is transudate? What cell types are most common?
transparent pleural effusion that is typically transparent and low in protein (<2.5-3 g/dl) and cells (<500-1000 /uL)
mononuclear cells - macrophages, lymphocytes, mesothelial cells
What is modified transudate? What cell types are the most common? What is it suggestive of?
serosanguinous pleural effusion with slightly higher protein (~3.5 g/dl) and cells (1000-5000 /uL) compared to transudate
neutrophils
obstructive effusion
What is exudate? What causes its accumulation? What is a key part to its diagnosis?
red, brown, yellow, or opaque pleural effusion with high protein (>3 g/dl) and cells (>5000 uL)
increased capillary permeability due to inflammation
aerobic and anaerobic cultures with susceptibility
What is pyothorax? When does the exudate typically have a foul odor? What causes sulfur granule accumulation?
septic pleural effusion with extremely elevated cell counts consisting of degenerate neutrophils and bacteria
if anaerobes are present
Nocardia and Actinomyces infection
What are the 4 most common causes of pyothorax in cats? What bacteria are the most common causes?
- penetrating bite wounds
- oropharyngeal aspiration
- upper respiratory infection
- foreign body (grass awn)
Pasteurella, Bacteroides, Fusobacterium
What are the 3 most common causes of pyothorax in dogs? What bacteria are the most common causes?
- inhaled foreign bodies
- penetrating injury
- pneumonia
Actinomyces, Nocardia
What do non-septic exudates typically look like? What are the 4 most common causes?
thick, yellow/straw-colored, rich in protein
- FIP
- chylothorax/hemothorax
- neoplasia
- lung torsion
What cell types are commonly seen in non-septic exudates?
VARIABLE
- neutrophils
- macrophages
- eosinophils
- lymphocytes