Pleural effusion

Question 1

What is a pleural effusion

Answer 1

• A pleural effusion is an accumulation of fluid in the plueral space
• Either exudate or transudate depending on its composition

Question 2

Exudate

Answer 2

• Exudate is fluid that leaks around the cells of the capillaries and is caused by inflammation, while transudate is fluid pushed through the capillary due to high pressure within the capillary
• An alteration of the local inflammatory factors that precipitate a pleural fluid accumulation represents an exudative effusion
• Exudate forms when protein permeability of the systemic capillaries is increased, causing an increase in pleural liquid protein concentration

Question 3

Transudate

Answer 3

• An imbalance between the hydrostatic and oncoticpressure within the capillaries causes a transudate effusion.

Question 4

Causes of exudative effusions

Answer 4

• Parapneumonic effusion ‘simple’ if pH >7.2 and ‘complicated’ if pH<7.2; empyema if frank pus on aspiration
• Malignancy
• Pulmonary emboli –> pulmonary infarction
• Rheumatoid arthritis
• Mesothelioma
• Pancreatitis
• Complication of acute myocardial infarction(dressler’s syndrome)
• TB

Question 5

Common causes of transudative effusions

Answer 5

Left ventricular dysfunction. 
• Cirrhotic liver disease. 
• Hypoalbuminemia. 
• Constrictive pericarditis. 
• Hypothyroidism. 
• Meigs’ syndrome – in conjunction with ovarian fibroma.
   Congestive heart failure
   Peritoneal dialysis 
   Ovarian hyperstimulation 
   Superior vena cava obstruction(usually due to lung cancer)

Question 6

Some less common causes of transudative effusions

Answer 6

Hypothyroidism, nephrotic syndrome, mitral stenosis and pulmonary embolism(tends to produce a comparatively small effusion but disproportionate dyspnoea and pleuritic pain; 8-% are exudates, 20% are transudates)

Question 7

Clinical features of pleural effusion

Answer 7

The accumulation of fluid within the pleural space will be asymptomatic until it is large enough to cause respiratory compromise or unless other symptoms lead to respiratory assessment.

Symptoms are breathlessness, particularly on exertion, and sometimes pleuritic chest pain.

The examination findings include decreased breath sounds, stony dull percussion note, and decreased expansion on the affected side

Question 8

Imaging investigations for pleural effusion

Answer 8

· CXR will confirm the presence of an effusion and whether it is bilateral or unilateral. It may show underlying malignancy, pleural plaques/thickening or heart failure. A repeat CXR should be performed after aspiration or chest drain insertion. PA film will usually suffice and, rarely, lateral views are needed.

· About 200 ml of fluid is required to be visible on a PA view but just 50 ml will cause costophrenic blunting on a lateral view.

Question 9

What are bilateral effusions caused by usually

Answer 9

· Bilateral effusions with an enlarged heart shadow are commonly caused by congestive cardiac failure.

Question 10

What might be seen on a chest x-ray with asbestos and pleural effusion

Answer 10

· Pleural plaques and calcifications may be seen, suggesting history of asbestos exposure.

Question 11

Other imaging investigations besides cxr

Answer 11

· Ultrasound is much more sensitive than CXRs for detecting pleural effusions and can detect even very small effusions

· Ultrasound is a useful tool in visualizing pleural fluid. Further to this, the British Thoracic Society strongly recommends inserting chest drains under direct ultrasound vision. The practice of ‘X marks the spot’, where tap sites are marked in the Radiology Department, is now discouraged.

· Contrast CT scanning may be required to further determine the underlying cause of the effusion.

Question 12

Pleural fluid abnormal pH

Answer 12

This can be done on a blood gas machine. A pH of <7.2 in conjunction with pneumonia implies an infected pleural space

Question 13

Protein test of pleural fluid

Answer 13

· Protein and lactate dehydrogenase(LDH) - this should be done with paired serum samples. Traditionally, effusions are divided into:

• Exudative - protein > 30 g/dL
• Transudative - protein < 30 g/dL

Question 14

Light’s criteria for pleural effusions

Answer 14

• If the serum protein is low then this is a less useful cut-off and Light’s criteria are more sensitive and specific. These state that if one of the following is true then the fluid is exudative:1) pleural fluid protein:serum protein >0.5
  2) pleural fluid LDH:serum LDH >0.6
  3) pleural fluid LDH >2/3 the upper serum reference range.

Question 15

Investigation if infection suspected

Answer 15

• Gram stain, culture and sensitivities: for bacterial infection. If there is suspicion of TB, then stain and culture for Mycobacterium spp. should be requested.

Question 16

Further secondary investigations

Answer 16

• Cytology: for malignancy and differential cell count. Further investigations may include pleural biopsy, thoracoscop and bronchoscopy and is likely to need specialist involvement. If the first pleural fluid cytology specimen is negative, it should be repeated.

Question 17

Approach to unilateral pleural effusion

Answer 17

• Does the clinical picture suggest a transudate (eg, left ventricular failure (LVF), hypoalbuminaemia, dialysis)?It is often possible to identify transudative effusions by clinical assessment alone:

• If YES, treat the cause. This may result in resolution. If it doesn’t, continue with pleural aspiration, as below.
• If NO, perform pleural aspiration. Ultrasound-guided pleural aspiration may be needed if the effusion is small or loculated.

Question 18

Pleural aspiration

Answer 18

• Pleural aspiration (thoracentesis): send aspirated fluid for cytology; protein; lactate dehydrogenase (LDH); pH; Gram stain, culture and sensitivity; acid-alcohol fast bacilli (AAFB) stains and culture.

Question 19

What should you do if you suspect an empyema, chylothorax or haemothorax

Answer 19

• If YES, perform additional pleural fluid tests:

• For empyema: centrifuge to differentiate from chylothorax.
• For chylothorax: cholesterol and triglyceride levels; centrifuge; presence of cholesterol crystals and chylomicrons.
• For haemothorax: haematocrit.

Question 20

Appropriate blood test investigations

Answer 20

• Perform other tests as appropriate: for example, blood tests (ESR, CRP, albumin, amylase, TFTs, blood culture). D-dimer and spiral CT are the best investigations if pulmonary embolism is suspected.

Question 21

CT of the thorax +/- abdomen

Answer 21

Usually carried out with contrast enhancement. This should be done before the effusion is drained and it has a high sensitivity for malignant pleural disease.[7]It can also show abdominal malignancy.

Question 22

Pleural biopsy

Answer 22

Samples should be sent for histology and TB culture; in mesothelioma, the biopsy site should be irradiated to stop biopsy site invasion by tumour. This can either be blind biopsy using an Abram’s needle, CT-guided biopsy or biopsy performed at the time of thoracoscopy.

Question 23

Test for rheumatoid disease

Answer 23

• Glucose and complement

Question 24

Test for pancreatitis

Answer 24

• Amylase

Question 25

Thoracoscopy

Answer 25

This allows direct visualisation of the pleura and can allow tissue diagnosis, fluid drainage and pleurodesis. It can be performed under conscious sedation.

Question 26

Bronchoscopy

Answer 26

BTS guidelines suggest that this investigation should be reserved for patients whose radiology suggests a mass or loss of volume or when there is a history of haemoptysis or possible foreign body aspiration.

Question 27

Should aspiration be performed for bilteral effusions

Answer 27

• The BTS suggests that ‘aspiration should not be performed for bilateral effusions in a clinical setting strongly suggestive of a pleural transudate, unless there are atypical features or they fail to respond to therapy’.

Question 28

Cuases of bloody pleural fluid

Answer 28

• Malignancy.
• Pulmonary embolus with infarction.
• Trauma.
• Benign asbestos pleural effusions.
• Post-cardiac injury syndrome.

Question 29

Pleural fluid haematocrit

Answer 29

if the pleural fluid is bloody, the haematocrit of the fluid should be measured. If the haematocrit of the pleural fluid is more than half of the patient’s peripheral blood haematocrit, the patient has a haemothorax. If the haematocrit of the pleural fluid is <1%, the blood in the pleural fluid is not significan

Question 30

Causes of pleural fluid pH<7.2 (normal pleural pH is 7.6)

Answer 30

• Pleural infection and empyema.
• Rheumatoid disease and systemic lupus erythematosus (SLE).
• TB.
• Malignancy.
• Oesophageal rupture

Question 31

Importance of cytology in testing pleural fluid

Answer 31

Malignant effusions are diagnosed by pleural fluid cytology alone in only 60% of cases. If the first pleural fluid cytology specimen is negative, it should be repeated.

Question 32

Chylothorax - cholesterol, triglycerides, cholesterol crystals and chylomicrons

Answer 32

• Chylothorax usually has a triglyceride level >1.24 mmol/L, cholesterol <5.18 mmol/L, no cholesterol crystals and the presence of chylomicrons.

Question 33

Pseudochylothorax - cholesterol, triglycerides, cholesterol crystals and chylomicrons

Answer 33

• Pseudochylothorax has a triglyceride level <0.56 mmol/L, cholesterol level >5.18 mmol/L, no chylomicrons and the presence of cholesterol crystals.

Question 34

Causes of low pleural glucose levels

Answer 34

causes of low pleural glucose levels (<3.3 mmol/L) are:

• Empyema.
• Rheumatoid disease.
• SLE.
• TB.
• Malignancy.
• Oesophageal rupture.

Question 35

Purpose of carrying out a differential white cell count

Answer 35

pleural lymphocytosis is common in malignancy and TB

Question 36

Pleural effusion management

Answer 36

• Management should be aimed at the underlying disease. If a transudate is confirmed, aspiration should be avoided.
• Small effusions that are not causing respiratory embarrassment may be managed by observation.
• Tapping the fluid can give symptomatic relief as well as being useful for diagnosis but the effusion is likely to re-form. Repeated tapping may be used in palliative care.
• No more than 1.5 litres should be removed at a single procedure, as fluid shifts can result in pulmonary oedema.[15]
• In malignant effusions, if no attempt is made at pleurodesis, nearly all have recurred within a month.
• A chest drain can also be inserted for controlled drainage of the effusion. The drain can be removed if/when the underlying disease has been treated. Chest drains are often needed for the management of empyema and haemothorax.
• Long-term indwelling pleural drainage may be used in some patients with malignant effusions.
• Pleurectomy is also used in some cases of malignant effusion when other treatment options have failed.
• Surgically implanted pleuroperitoneal shunts are occasionally used for the treatment of malignant effusions and chylothorax.

Question 37

What is pleurodesis

Answer 37

Pleurodesis
• This is injection of a sclerosant to cause adhesion of the visceral and parietal pleura and to help to prevent reaccumulation of the effusion. Sclerosing agents that are commonly used include tetracycline, sterile talc and bleomycin.
• It is most often used in the management of recurrent malignant effusions.

Question 38

Prognosis

Answer 38

• This is dependent on the cause of the effusion.
The presence of a malignant pleural effusion is associated with a poor prognosis with median survival following diagnosis ranging from 3 to 12 months depending on cell type