Pleural Effusion

Question 1

Pleural Effusion

Answer 1

Pleural effusion= Accumulation of fluid in the pleural space. It can be classified as exudative or transudative, according to protein concentration.

Question 2

Pleural Effusion: Classification

Answer 2

Pleural effusions can be broadly categorised into:
* Exudative – a high protein content (more than 30g/L)
* Transudative – a lower protein content (less than 30g/L)

Light’s criteria uses pleural fluid/serum protein or lactate dehydrogenase (LDH) to establish if a pleural fluid is an exudative effusion:
* Pleural fluid protein: serum protein ratio > 0.5
* Pleural fluid LDH / serum LDH > 0.6
* Pleural fluid LDH > 2/3 of the normal upper limit of the serum LDH

Malignancy-caused pleural effusions are generally serosanguinous exudates with low glucose and low pH and sometimes have elevated WBC counts. A mesothelioma may cause a heavily blood-stained pleural effusion. Pleural fluid cytology can be used to check for malignant cells, which can aid diagnosis but is only positive in roughly 50-60% of cases.

Question 3

Pleural Effusion: Aetiology

Answer 3

Exudative causes are related to inflammation. The inflammation results in protein leaking out of the tissues into the pleural space (ex- meaning moving out of) due to increased capillary permeability.
The top causes are:
infection
* pneumonia (most common exudate cause)
* tuberculosis
* subphrenic abscess
connective tissue disease
* rheumatoid arthritis
* systemic lupus erythematosus
neoplasia
* lung cancer
* mesothelioma
* metastases
pancreatitis
pulmonary embolism
Dressler’s syndrome
yellow nail syndrome

Transudative causes relate to fluid moving across or shifting into the pleural space (trans- meaning moving across) due to increased hydrostatic pressure or decreased oncotic pressure. The top causes are:
* Congestive cardiac failure
* Hypoalbuminaemia
* Hypothyroidism
* Meigs syndrome (a triad of a benign ovarian tumour (usually a fibroma), pleural effusion and ascites. The pleural effusion and ascites resolve with the removal of the tumour).

Question 4

Pleural Effusion: Presentation

Answer 4

Symptoms:
* shortness of breath
* non-productive cough
* chest pain
Examination findings:
* Dullness to percussion over the effusion
* Reduced breath sounds
* Tracheal deviation away from the effusion in very large effusions

Question 5

Pleural Effusion:
Investigations

Answer 5

Imaging
* posterioranterior (PA) chest x-rays should be performed in all patients
* ultrasound is recommended: it increases the likelihood of successful pleural aspiration and is sensitive for detecting pleural fluid septations
contrast CT is now increasingly performed to investigate the underlying cause, particularly for exudative effusions
Chest x-ray findings are:
* Blunting of the costophrenic angle
* Fluid in the lung fissures
* Larger effusions will have a meniscus (a curving upwards where it meets the chest wall and mediastinum)
* Tracheal and mediastinal deviation away from the effusion in very large effusions

Ultrasound and CT can detect smaller effusions than a chest x-ray, estimate the volume and identify potential causes.

Pleural fluid analysis requires a sample taken by aspiration or chest drain. This helps establish the underlying cause by measuring the protein content, LDH, cell count, pH, glucose and microbiology testing.

pleural tap shows evidence of pleural infection (e.g. pH < 7.2 or turbid pleural fluid

Question 6

Pleural Effusions: Treatment

Answer 6

Diagnosing and treating the underlying cause is the mainstay of management.
* small effusions will resolve with treatment of the underlying cause
* More significant effusions often need aspiration or drainage.

Question 7

Pleural Effusion: Complications - Empyema

Answer 7

Empyema= an infected pleural effusion. Suspect an empyema in a patient with improving pneumonia but a new or ongoing fever. Pleural aspiration shows pus, low pH, low glucose and high LDH. Empyema is treated with a chest drain and antibiotics.

Answer 8

British Thoracic Society (BTS) state that the following are the main indications for placing a chest tube in pleural infection:
* Patients with frankly purulent or turbid/cloudy pleural fluid on sampling should receive prompt pleural space chest tube drainage.
The presence of organisms identified by Gram stain and/or culture from a non-purulent pleural fluid sample indicates that pleural infection is established and should lead to prompt chest tube drainage.
Pleural fluid pH < 7.2 in patients with suspected pleural infection indicates a need for chest tube drainage.

immediate chest drain insertion as she is stable.