Pleural Effusion

Question 1

What is pleural effusion?

What mechanisms lead to pleural effusion.

Answer 1

Build up of fluid into the pleural space.

3 main underlying mechanisms lead to pleural effusion.

Transudative effusion
- Increase in hydrostatic pressure: heart failure –> increase in pulmonary pressure –> increase in hydrostatic pressure within the pulmonary capillaries –> effusion into the pleural space.

• Decrease in oncotic pressure (due to a lack of proteins e.g. albumin). Lack of proteins can be due to issues with protein production in the liver (e.g. cirrhosis), excessive loss of protein at the kidneys (nephrotic syndrome) or lack of absorption of proteins at the gut (malabsorption).

Exudative effusion
- Inflammation of the pulmonary vessels leads to large gaps being opened in between the endothelial cells lining capillary walls –> exudation of fluid, proteins (e.g. lactate dehydrogenase) and immune cells into the pleural space. Inflammations can be due to trauma, malignancy, infection, PE, inflammatory disorders e.g. SLE, RA ; Dressler’s syndrome and yellow nail syndrome as well.

Lymphatic effusion (chylothorax)
- Damage to the thoracic duct or compression of the duct via a mediastinal mass, leads to the accumulation of fluid into pleural space.

Question 2

What are the underlying causes of pleural effusion.

Answer 2

Transudative causes
- Heart failure (most common cause)
- Hypoalbuminaemia
> Liver cirrhosis 
> Nephrotic syndrome 
> Malabsorption 
- Hypothyroidism 
- Meig's syndrome --> right sided pleural effusion, with ovarian malignancy 

Exudative causes

• Trauma
• Infection (e.g. pneumonia, TB, subphrenic abscess formation) –> with infective causes, infection may spread to the pleural space.
• -> Malignancy - mesothelioma, lung cancer, metastasis
• -> Inflammatory disorders: SLE, RA
• -> Dressler’s syndrome
• -> Yellow nail syndrome

Lymphatic causes

• Damage to the thoracic duct e.g. surgery
• Compression of the thoracic duct e.g. mediastinal mass

Question 3

What is the typical presentation of a pleural effusion?

Answer 3

• SOB
• Dullness to percussion over the effusion
• Decreased tactile fremitus (vibrations absorbed by the excess fluid)
• Reduced breath sounds on auscultations
• Tracheal deviation away from the effusion if massive.

Question 4

What investigations can be carried out for a pleural effusion?

Answer 4

Chest X ray (posterior - anterior)
> Standing Up –> blunting of the costophrenic angle,
> Fluid in lung fissures
> Larger effusions will have a meniscus, where the fluid meets the chest wall and the mediastinum
> If effusion is massive, will lead to tracheal deviation and mediastinal shift.

Fluid aspiration (thoracocentsis) to assess for underling transudative vs exudative cause. Carry out fluid aspiration under ultrasound guidance. Fluid should be sent out for pH, protein, lactate dehydrodenase, cytology and microbiology

Transudative cause: protein < 30g/L

Exudative cause: protein > 30g/L

If protein is between 25-35g/L, then apply Light’s criteria.

An exudative cause is likely if:
> pleural fluid protein/ serum protein > 0.5

> pleural fluid LDH/serum LDH > 0.6

> pleural fluid LDH is more than 2/3 of the upper limit of normal serum LDH.

Other characteristic findings

• low glucose: TB, RA
• high amylase: oseophageal perforation, pancreatitis
• heavy blood staining: TB, mesothelioma, PE

Also, if cause is infective (exudative), then:

• if pleural fluid is purulent or cloudy/turbid, then insert chest tube.
• if pleural fluid is clear, but pH is less than 7.2 and patient is likely to have infective pleural fluid, then insert chest tube.

Question 5

How do you manage pleural effusions?

Answer 5

Conservative management effusion may be appropriate for small effusion (heart failure), as small effusions will resolve with the treatment of the underlying cause.

For example, treatment of heart failure with diuretics and applying sodium restrictions will help to treat the heart failure and therefore the pleural effusion.

If the pleural effusion is very large, then aspiration or drainage with a tube is necessary.

In large located effusions like exudative pleural effusions with pneumonia, or TB, then surgery might be necessary as the effusion can thicken into an empyema which may not drained easily via tube.

Other approaches
- Pleurodesis - inserting an irritant drug to stick the visceral and parietal pleura together.

Question 6

What is an empyema?

When should you suspect an empyema?

How do you treat an empyema?

Answer 6

Empyema is where there is an infected pleural effusion.

Suspect an empyema in a patient who has improving pneumonia, but new or ongoing fever.

Pleural aspiration would show pus, acidic pH (pH< 7.2), low glucose, and high LDH.

An empyema should be treated via a chest drain to remove the pus, plus antibiotics. In some cases, surgery might be necessary.