QuestionSBA
QuestionChoice
Pulmonary embolism tends to cause a transudative pleural effusion, and this history here does not indicate PE
32204
b
Pulmonary embolism (PE)
QuestionChoice
This patient has an exudative effusion fulfilling Light's criteria, with pleural fluid/serum LDH ratio >0.6 and pleural fluid LDH >2/3 the upper limit of normal serum LDH. Parapneumonic effusions may occur with bacterial pneumonia, and may cause either simple or complicated effusions (including empyema). This would usually show up on pleural tap as purulent pleural fluid with neutrophil predominance, pH <7.3, low glucose and raised LDH. Clinical presentation may be similar to that of pneumonia
32203
a
Bacterial pneumonia
QuestionChoice
Whilst malignancy often causes a exudative effusion, this is unlikely given her young age and more recent onset of symptoms
32205
c
Malignancy
QuestionChoice
In rheumatoid pleurisy, pleural fluid is likely to be low in glucose with raised LDH and pH <7.3, which is rather similar to the pleural fluid results in this patient. However, the history is not suggestive of rheumatoid arthritis
32207
e
Rheumatoid arthritis
QuestionChoice
Pulmonary embolism tends to cause a transudative pleural effusion, and this history here does not indicate PE
32206
d
Heart failure
QuestionComment
How is this exudative?? The protein isn't more than 30g/L on either of them?
6276
QuestionComment
Use light's criteria when protein is between 20-30 (some textbooks say 25-35)
10021
User
subscriber
Myotonia Bladder
QuestionComment
But the protein is only 11 @ myotonia bladder ??
11121
User
subscriber
Abscess Otitis
User
subscriber
Yellow Stasis
QuestionComment
this question is pure bs. the protein is literally 11g/L. its transudative by definition.
15907
User
subscriber
Migraine Complement
QuestionComment
lights criteria states that if pleural protein/serum protein=<0.5 then that is transudative 
37622
User
subscriber
Imran
QuestionComment
Also this was misleading - ''She has visited her General Practitioner and has completed a 5 day course of antibiotics with no improvement.'' if her presentation was bacterial pneumonia should have been some improvement 
43265
User
subscriber
Anna
Concept
Chapter
# Summary

A pleural effusion refers to abnormal fluid accumulation in the pleural cavity. There is a wide range of causes, which are classified into transudative and exudative effusions. Transudates include effusions secondary to heart failure or cirrhosis, and typically have low protein levels in the pleural fluid. Exudates include effusions due to malignancy or infection, and have higher protein levels in the fluid. Key investigations include a pleural tap to sample the fluid, chest X-ray to detect an effusion and further imaging and bloods to investigate for underlying causes (e.g. a CT chest if malignancy is suspected). Treatment depends on the underlying cause, but larger effusions or empyemas should be drained. Options for recurrent effusions include pleurodesis or an indwelling chest drain.

# Definition

A pleural effusion is a collection of fluid in the pleural cavity (space between the lung and the chest wall). In health, there is a small volume of serous pleural fluid (10-20ml) which lubricates the pleura and creates surface tension. When larger volumes of fluid accumulate this overwhelms the resorption capacity of the pleura and can impede respiration as the lung cannot expand fully.

# Aetiology

Causes of pleural effusions are classified as either **transudates** (where changes in oncotic and hydrostatic pressure cause fluid to leak from the vasculature) or **exudates** (where inflammation leads to increased microvascular permeability and drainage of pleural fluid may be impaired).

**Examples of transudative causes include:**

- Heart failure
- Nephrotic syndrome
- Cirrhosis
- Hypoalbuminaemia

**Examples of exudative causes include:**

- Pneumonia (a “parapneumonic effusion”) 
- Malignancy
- Tuberculosis
- Pulmonary embolism
- Rheumatoid arthritis
- Systemic lupus erythematosus 
- Pancreatitis 
- Trauma

# Classification

Transudates are classified as pleural fluid with a protein level less than 25g/L (assuming a normal serum protein).

Exudates are classified as pleural fluid with a protein level more than 35g/L.

For intermediate effusions, **Light’s criteria** are used - if any of the following are true then the effusion is an exudate:

- The ratio of pleural to serum protein is greater than 0.5
- The ratio of pleural to serum LDH is greater than 0.6
- The pleural fluid LDH is greater than ⅔ of the upper limit of normal serum value

# Signs and symptoms

Patients may be asymptomatic, especially if their lung function and capacity are normal, and so many effusions are detected incidentally on imaging. 

Symptoms as effusions enlarge include:

- Shortness of breath
- Reduced exercise tolerance
- Dry cough
- Pleuritic chest pain

On examination, signs include:

- Reduced chest expansion on the affected side
- Dullness to percussion over the effusion
- Reduced or absent breath sounds over the effusion
- Loss of vocal resonance over the effusion
- Large pleural effusions may cause tracheal deviation away from the effusion
- Respiratory distress (e.g. accessory muscle usage) 

Symptoms and signs of an underlying cause of the effusion may also be seen, for example peripheral oedema in a patient with an effusion secondary to congestive cardiac failure. 

# Differential diagnosis

Other than the causes listed above, other types of fluid can accumulate in the pleural cavity - these may also be thought of as types of pleural effusion but don’t fit into the transudate/exudate classification and have different causes and management:

- **Haemothorax** - a collection of blood in the pleural cavity, usually secondary to trauma but can occur spontaneously e.g. in the context of malignancy or vascular rupture
- **Chylothorax** - chylous fluid in the pleural cavity, occurs due to lymphatic duct injury or obstruction (leading to rupture of small collaterals). Common causes include iatrogenic injury during thoracic surgery, traumatic injury or lymphoma.
- **Empyema** - a collection of pus in the pleural cavity, may be loculated with gas. Usually develop as a complication of pneumonia.
- **Mesothelioma** - tumour of the pleura, strongly associated with asbestos exposure.

# Investigations

**Bedside investigations:**

- A **pleural tap** should be done in all new suspected exudative effusions, as well as those presumed to be transudates (e.g. bilateral, associated features of heart failure) if they fail to respond to treatment or have atypical features.
- Pleural fluid is aspirated and sent for cytology, MC&S (microscopy, culture and sensitivity) and biochemistry (pH, protein, LDH and glucose).
- Paired serum protein and LDH should also be sent.
- Other investigations may be requested for a suspected underlying cause, e.g. pleural fluid amylase (raised in an effusion secondary to pancreatitis).
- Pleural fluid cholesterol and triglycerides are raised in a chylothorax.
- Low glucose is seen in effusions secondary to rheumatoid arthritis, SLE and in empyemas.
- Complement is also low in effusions secondary to rheumatoid arthritis or SLE.
- pH<7.2 indicates either infection (e.g. an empyema) or malignancy.
- Bloody pleural fluid can be seen in malignancy, trauma or PE - haematocrit measurement of the pleural fluid is used to determine if it is a haemothorax.
- Other bedside tests should be targeted to the underlying cause e.g. sputum AFB for TB, urinalysis looking for proteinuria in suspected nephrotic syndrome.

**Blood tests:**

- FBC - may show a raised WCC suggestive of infection, anaemia or thrombocytosis in malignancy
- U&E - for baseline renal function especially if diuretic treatment is considered
- LFTs - may show a low albumin in cirrhosis 
- Clotting - to indicate safety for pleural intervention
- ANA, rheumatoid factor - if a rheumatological cause such as SLE or rheumatoid arthritis is suspected
- Serum amylase - if pancreatitis is suspected

**Imaging:**

[lightgallery]


- Chest X-ray is the first-line imaging investigation in all patients with a suspected pleural effusion 
- will reveal blunting of the costophrenic angle or white-out of lung (if large)

- Thoracic ultrasound 
- can reveal whether it is simple fluid or septated, which would be consistent with malignancy or infection
- underlying changes in the lung can also be identified such as consolidation or pulmonary oedema.

- CT scan with contrast 
- can be used to further investigate an underlying cause e.g. malignancy

**Other investigations:**

- Pleural biopsy may also be considered if pleural fluid analysis and imaging do not reveal a diagnosis - samples should be sent for histology and TB culture.

- Echocardiogram in suspected heart failure

- Fibroscan in suspected liver cirrhosis

# Management

**Conservative:**

- Symptom management e.g. analgesia for chest pain
- Oxygen if low saturations
- May require resuscitation (use an ABCDE approach) if unstable due to a large effusion 

**Medical:**

- Antibiotics for infection - may need a prolonged course for empyema along with drainage
- Diuretics for pleural effusions secondary to heart failure

**Interventional**

- Ultrasound-guided pleural aspiration may be used for symptomatic relief 
- A chest drain is needed for empyemas and haemothoraxes, and for some larger effusions
- If pleural effusions are rapidly recurring, the two main options are pleurodesis or a tunnelled indwelling pleural drain
- Indwelling drains are often used in patients receiving palliative treatment (e.g. of a malignancy) as they can have regular drainage in the community, reducing hospital admissions
- Pleurodesis can be chemical (where an irritant is injected into the pleural space, sealing it shut via a fibrotic reaction) or surgical via thoracotomy or thoracoscopy

# References

[Radiopaedia - Pleural Effusion](https://radiopaedia.org/articles/pleural-effusion?lang=gb)

[Patient UK - Pleural Effusion](https://patient.info/doctor/pleural-effusion-pro)

[Life in the Fast Lane - Pleural Fluid Analysis](https://litfl.com/pleural-fluid-analysis/)
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Picture
A large right sided pleural effusion.
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Pleural effusion.jpeg
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2651
Pleural effusion
Topic
20
Respiratory Physiology
Bacterial pneumonia
6441
A 40 year old female is admitted to the general medical ward with a 2 week history of fever, worsening shortness of breath and a productive cough with yellow sputum. She has visited her General Practitioner and has completed a 5 day course of antibiotics with no improvement. She has no other past medical history of note.



On examination, she has right sided coarse crepitations with reduced air entry in the right lower zone.



Chest X-ray: Right sided pleural effusion



The respiratory registrar performs a diagnostic pleural tap. The results are as follows:



Appearance - Purulent
Microscopy - Neutrophil predominant
pH - 7.28



||Pleural fluid|Serum|
|---------------------------|-------------|----------|
|Protein|11 g/L|28 g/L|
|Lactate dehydrogenase (LDH)|358 U/L|465 U/L|
|Glucose|2.8 mmol/L|6.9 mmol/L|



Given the pleural fluid results, which is the most likely cause of her pleural effusion?
a