Pleural Disease

Question 1

The surface of the inner wall of body cavities is lined by what?

Answer 1

A serous membrane/serosa.

Question 2

What are the components of a serous membrane?

Answer 2

Single layered flat mesothelial cell layer, with underlying propria (connective tissue).

Question 3

What is the pleura?

Answer 3

The serous membrane in the thoracic cavity.

Question 4

What is the peritoneum?

Answer 4

The serous membrane in the abdominal and pelvic cavities.

Question 5

What covers the surface of the lung?

Answer 5

The visceral (pulmonary) pleura. 
It is reflected around the root of the lung and becomes continuous with the mediastinal pleura.

Question 6

What are parietal pleura?

Answer 6

Mediastinal, diaphragmatic and costal pleura.

Question 7

What drains the pleural cavity?

Answer 7

The pleura contains a rich lymphatic system that drains the pleural cavity.

Question 8

What is the pleural cavity?

Answer 8

The narrow space between the parietal and viscera pleura.

Question 9

What does the pleural cavity contain?

Answer 9

It contains a small amount of serous fluid spread over the surface of the pleura ~ 0.1ml/kg.

Question 10

What is the role of the pleural cavity?

Answer 10

Establishes adhesion.

Smooth movement.

Question 11

What is the mediastinum?

Answer 11

The space between the left and right pleural sacs around the lungs. It is more or less in the midline of the thorax. It is continuous in most species. It is more delicate and discontinuous in horses. It is thin in dogs/cats.

Question 12

What is pleural space disease?

Answer 12

Accumulation of fluid (pleural effusion), air (pneumothorax), soft tissue mass (e.g. abdominal organs).
As fluid / air etc. accumulate in the pleural space, the resultant loss of negative pressure causes the lungs to collapse due to the loss of elastic recoil.
Fluid etc. restricts the ability of the lungs to inflate –> restrictive lung disease.

Question 13

What are the clinical signs of pleural space disease?

Answer 13

Clinical signs and severity depends on the quantity of fluid / air / mass present.
Clinical signs include:
“Restrictive” breathing pattern
Short, shallow breaths
Tachypnoea
Open mouth breathing
Dyspnoea, Respiratory distress
Orthopnoea
elbow abduction, sternal recumbency
Cyanosis

May be acute or chronic.

Question 14

What is involved in pleural fluid turnover?

Answer 14

Fluid is produced mainly from parietal pleural vessels by capillary filtration.
Fluid is reabsorbed primarily via parietal lymphatic vessels.

Question 15

Pleural effusion is often an aspect of pleural space disease. What is pleural effusion controlled by and why does it occur?

Answer 15

It is controlled by Starlings’ forces.
It occurs when pleural fluid dynamics favours decreased pleural fluid absorption or increased fluid formation.
Pleural fluid can be unilateral but is usually bilateral.

Question 16

What causes increased fluid formation?

which contributes to pleural effusion

Answer 16

“Leaky” capillaries (e.g. pleural inflammation).
Increase in intravascular pressure (e.g. CHF).
Increase in lung interstitial fluid (e.g. CHF).
Decrease in pleural pressure.
Increase in pleural fluid protein.
Disruption of thoracic duct or blood vessels.

Question 17

What causes decreased fluid absorption?

which contributes to pleural effusion

Answer 17

Obstruction of draining lymphatics (e.g. neoplasia, inflammation).
Increased systemic vascular pressures (right heart failure).
Reduced vascular oncotic pressure (hypoalbuminaemia).

Question 18

What can be observed when there is an accumulation of fluid (pleural effusion) in pleural space disease?

Answer 18

Auscultation: muffling of lung and heart sounds especially ventrally (when standing).
Percussion: increased dullness (fluid “line”),
A number of different fluid types can be present:
- Transudate
- Modified transudate
- Exudate
–Non-septic
–Septic
–Blood
–Chyle

Question 19

What is the most common cause of pure transudate formation?

Answer 19

Decreased oncotic pressure- hypoalbuminaemia.

Question 20

What is the most common cause of modified transudate formation?

Answer 20

Increased hydrostatic pressure - right sided heart failure (pericardial disease, pulmonic stenosis, tricuspid dysplasia, cardiomyopathy, pulmonary hypertension).

Question 21

What can cause non-septic effusion/exudate?

Answer 21

FIP, neoplasia, chronic chylothorax, chronic lung lobe torsion, fungal infection.

Question 22

What can cause septic effusion (pyothorax)?

Answer 22

Penetrating chest wound, foreign body inhalation (grass seed), ruptured oesophagus, ruptured pulmonary abscess / tumour, haematogenous bacterial spread.

Question 23

What can cause chyle effusion (chylothorax)?

Answer 23

Disruption of the thoracic duct!
- Lymphangiectasia, cranial vena cava obstruction, neoplasia, heart disease, fungal infection, lung lobe torsion, diaphragmatic hernia, trauma of the thoracic duct.

Question 24

What can cause blood effusion (haemothorax)?

Answer 24

Trauma, coagulopathy, neoplasia, lung lobe torsion.

Question 25

Can you see pleural effusion on diagnostic imaging?

Answer 25

Yes. For example, radiographs and ultrasound.
It is less stressful for the patient using ultrasound. Stick it on the side of the chest and you can very quickly make a diagnosis of effusion.

Question 26

What should be done in the initial management of pleural disease?

Answer 26

Oxygen supplementation
Emergency thoracic u/s to make diagnosis
Immediate throacocentesis

Question 27

What should you never do in severely dyspnoeic patients?

Answer 27

DO NOT RADIOGRAPH. These patients are very unstable and will die if they are stressed!

Question 28

What are the benefits of doing an immediate thoracocentesis?

Answer 28

Immediate relief from clinical signs.
Diagnostic - cytology, cell counts, protein content, bacterial culture.
Stabilise the patient prior to further investigations.

Question 29

What is involved in thoracocentesis?

Answer 29

Local anaesthetic rarely needed unless large bore catheter.
Clip area – if possible use quiet clippers (minimal stress esp. cats).
Quickly surgically prepare skin.
Butterfly needle / catheter at ICS 6-8.
Ideally localise large pocket of fluid with u/s first.
Use 20ml syringe, 3 way tap and extension set.
Aseptic technique.

Question 30

What are the indications for thoracostomy/chest drains?

Answer 30

Animals that will require multiple thoracocentesis over a short period of time.
If large volumes of effusion.
Pneumothorax.
Chest wall injuries - flail chest / flail segment.
Bite wounds.
Most pyothorax cases.

Question 31

What is one of the most important considerations in the management of pleural disease?

Answer 31

Treat the primary cause where possible.

Question 32

What Tx. would you provide for the pleural effusion in a case of heart failure?

Answer 32

Treat the primary cause - the heart failure. Stabilise the heart failure and the pleural effusion becomes less of a problem on its own.

Question 33

What Tx. would you provide for pericardial effusion?

Answer 33

Treat the effusion via drainage etc.

Question 34

What Tx. would you provide for a pyothorax?

Answer 34

Antibiotics, systemic & local (broad spectrum and treat anaerobes).
Be aware - often cultures will come back as negative!
Lavage?
Long course of treatment, guarded prognosis.

Chest is full of purulent material – want to get rid of as much of that as possible, will often be putting in chest drains to keep it drained as often as you can, very aggressive use of antibiotics ideally with culture and sensitivity, and not forgetting the anaerobes present because it becomes quite an anaerobic space in the pleura.

Question 35

What Tx. would you provide for a chylothorax?

Answer 35

Diet, surgery.

May try medical treatment first and then if not successful - surgery.

Question 36

What can cause accumulation of air (pneumothorax)?

Answer 36

Rupture of major airways / lung parenchyma.
Thoracic trauma.
Penetrating wounds.
Perforation of the oesophagus.
Bullous, necrotising or neoplastic lung disease.
Iatrogenic.

Question 37

What would you observe with pneumothorax?

Answer 37

Auscultation - reveals dull lung sounds dorsally, increased sounds ventrally (bronchovesicular).
Percussion – increased resonance.

Question 38

What is the pathogenesis behind an pneumothorax?

Answer 38

Can be traumatic, iatrogenic, spontaneous or infectious.

see lecture for examples

Question 39

What is the pathophysiology behind an pneumothorax?

Answer 39

Loss of coupling efficiency between the elastic rib cage and elastic lungs. This leads to partial lung collapse, decreased tidal volume and increase in overall lung volume due to expansion of the rib cage.
Severity of clinical signs depend on the degree of pneumothorax and the extent and presence of other pathology.

Question 40

What is tension pneumothorax?

Answer 40

Leads to severe lung compression and a severe and profound hypoxaemia develops.
Equilibration of pleural pressure and CVP develops leading to reduced venous return leading to reduced CO.
Hypoxaemia, hypercapnia and systemic hypotension develop and are rapidly life threatening.

Associated with a one way valve leak.
As the animal continues to breathe -> more and more air forced out of the lungs into the pleural space.

Question 41

How would you diagnose an pneumothorax?

Answer 41

Physical examination.
Assessment of respiratory status.
Thoracic radiographs – if stable enough. 
[Routine haematology / biochemistry]
Blood gases
Pulse oximetry

Question 42

How to deal with a pneumothorax case?

Answer 42

Oxygen.
Assess patient, dull lung sounds caudodorsally, hyper resonance on percussion.
Drain pneumothorax as necessary, avoid over drainage.
Many with strict cage rest will recover, strict cage rest for 2 weeks after.
Some will require chest drains and Heimlich valve.
If no improvement then surgical exploration and correction will be required.
If open wounds then sterile dressings and surgery as soon as patient is stable.

Question 43

What is the Heimlich valve?

Answer 43

A one way valve.
Air can come out of the chest and you can drain it, but it won’t got back in and leak – so stops any build up of pressure within the chest by having Heimlich valve on
^obviously have to be careful with these during surgery for example – e.g. if there are open wounds etc. – don’t want drainage into open wound.

Question 44

What is common history and causes for spontaneous pneumothorax? How would you diagnose this?

Answer 44

History - dyspnoea, anorexia, vomiting, most present with rapid progression of respiratory distress.
Most common cause is ruptured pulmonary bulla or sub pleural bleb.
Diagnosis is the same as for traumatic pneumothorax.

Question 45

How to deal with a case of spontaneous pneumothorax?

Answer 45

Medical management to stabilise until diagnostic tests decide whether surgical intervention is required.
Lobectomy as necessary.
Prognosis is dependent on the underlying cause.

Question 46

What is pneumomediastinum?

Answer 46

The abnormal presence of air or another gas in the mediastinum.