Pleural effusion

Question 1

What are the methods by which a transudate/ modified transudate can be made?

Answer 1

• Increased capillary hydrostatic pressure
• Decreased intravascular oncotic pressure
• Impaired lymphatic drainage
• Increased capillary permeability

Question 2

What are the classifications of pleural effusion?

Answer 2

Systemic:
- Transudates
- Modified transudates
Local:
- Septic and non septic exudates
- Chylous
- Haemorrhagic
- Neoplastic

Question 3

What laboratory analysis should be performed on an effusion

Answer 3

EDTA for cell counts
Serum gel tube
Plain tube for culture
In house cytology
Particularly helpful when infection, inflammation
or neoplasia are possible

Question 4

How much fluid is needed to cause respiratory distress?

Answer 4

30-60ml

Question 5

How can ultrasound examination help?

Answer 5

Direct thoracocentesis
Transudates usually anechoic
Haemorrhage, chyle and pus usually echoic usually echoic
Pleural thickening & septation may suggest:
▪ chronic inflammation
▪ Mesothelioma?

Question 6

Outline pyothorax

Answer 6

Normally cause unknown, can be d/t bite/ trauma/ FB
Can be insidious cause, presentation quite delayed and slow
Abscence of bacteria does not exclude - need to do culture!

Question 7

What are the most common bacterial isolates of a pyothorac

Answer 7

Anaerobic bacteria and gram positive filamentous organisms (Actinomyces/ Nocardia) most common in dogs
Pasteurella/ anaerobes most common in cats

Question 8

What bedside lab tests can you do to suggest a pyothorax?

Answer 8

Glucose < 1.7 and pH <6.9 is suggestive

Question 9

How do you treat a pyothorax>

Answer 9

Amox clav or MTZ with another good
Bilateral chest tubes - want the tip at the second rib space
Lavage and drain until clear - BID (roll around to move fluid)
Normally needs to be in for approx 7d.
In some cases medical oral management can cure

Question 10

What is the px for pyothorax

Answer 10

0- 40% mortality

If no improvement within 48- 72 hours - surgical exploration for FB

Question 11

Outline chylethorax

Answer 11

 Results when chyle from the cisterna chyli-thoracic duct system gains access to the pleural space
 Chyle is a milky fluid consisting of lymph and emulsified fats
 Fluid drained from the mesenteric lymphatic vessels to a large lymphatic saccular reservoir

Question 12

What is the thoracic duct?

Answer 12

continuation of the cisterna chyli that returns lymph from intestine intestine to the venous system via a lymphaticovenous junction in the cranial thorax

Question 13

What is the aetiology of chylethorax

Answer 13

Transmural leakage or chyle or trauma
Most commonly idiopathic
Or secondary to:
 Heart disease 
 Neoplasia
▪ thoracic wall, lymphatic or mediastinal
 Vena caval thrombosis
 Lung lobe torsion
 PPDH
 Congenital abnormalities of the thoracic duct

Question 14

How do you diagnose chylethorax?

Answer 14

 Chyle is typically white or pink-white
 Anorexic patients may have clear effusion
 Fluid triglyceride concentration > serum triglyceride concentration
 Fluid cholesterol < or = to serum cholesterol

Question 15

How do you ix chylethorax

Answer 15

Look for cause with imaging - u/s, rads

cytological exam will help to rule out neoplasia

Question 16

How do you treat chylethorax medically?

Answer 16

Repetitive thoracocentesis
Rutin
low fat diet
Not always successful

Question 17

If medical management of chylethorax doesn’t work, what should you do?

Answer 17

Ligation of caudal thoracic duct
The rational is this will lead to the formation of new lymphaticovenous anastamoses as a result of blocking the flow of chyle into the thorax
Succes = <60% dogs
21-53% cats
Sometimes failure is d/t failure to ligate all the collateral branches of the TD, increaed RHS venous pressures, pulmonary lymphatic fluid production, pleuritis
Concurrent pericardial thickening may impede lymphatic drainage - pericardiectomy sometimes performed at the same time

Question 18

What are the main causes of haemothorax?

Answer 18

trauma
coagulopathy
neoplasia
parasites
lung lobe torsion

Question 19

How do you dx haemothorax

Answer 19

Blood without plateles, doesn’t clot, but PCV same as body

Question 20

How do you manage haemothorax>?

Answer 20

If mild, manage conservatively - absorbs in 90 hours

Moderate - partial thoracocentesis, consider auto transfusion (if not neoplastic)

Question 21

What are the main neoplasias causing pleural effusion?

Answer 21

lymphoma
metastatic carcinoma
thymic most common in cats

Question 22

How useful is cytology in neoplastic effusions?

Answer 22

If roun cell normally quite good, harder with epithelial

hard to dx mesothelioma - often needs a pleural biopsy

Question 23

How do you treat neoplastic effusions

Answer 23

Lymphoma- systemic tx
intracavitary can be used for mesotheliomas and carcinomas
Can sometimes drain and leave ports in

Question 24

What is a tension pneumothorax?

Answer 24

One way valve created - leads to death

Question 25

What can cause a pneumothorax?

Answer 25

Blunt trauma
penetrating injuring
iatrogenic following FNA/ Sx? Biopsy
Spontaneous - from bulla, leaking via abscess or neoplasia, migrating FB

Question 26

How do you treat a pneumothorax?

Answer 26

Drain if dyspnoeic / recurrent
Tx initialing cause
Sx if no cuase obvious/ recurrent

Question 27

What are idiopathic effusions?

Answer 27

inflammatory exudate

many will have un dx mesothelioma or metastatic carcinoma

Question 28

What are the misc causes of effusions

Answer 28

FIP - Pyogranulomatous inflammation
- IFAT on macrophages from effusions has a moderate
sensitivity and high specificity for diagnosis

Idiopathic - steroids may help