Pleural Space

Question 1

The clinical importance of the pleural space in pleural effusion

Answer 1

-Pleural space: negative pressure
-As pleural fluid collects in the space, the pressure changes and becomes positive
-Changes again when fluid is drained out of lung; pressure change can cause cough and chest pain/ tightness

Question 2

What can accumulate in the pleural space?

Answer 2

-Air: PTX
-Proteinaceous fluid: exudative pleural effusion
-Protein deficient fluid: transudative pleural effusion
-Blood: haemothorax
-Chyle (fluid from lymphatic system): Chylothorax
-Fluid and air: hydropneumothorax
-Pus: empyema
-Tumour: primary or secondary (benign or malignant)
-Asbestos fibres: pleural plaque disease

Question 3

Physiology of pleural fluid accumulation

Answer 3

• Increased interstitial fluid in lung (LVSD, CAP, PTE)
• Increased intravascular pressure in the pleura (LVSD, SVCO, RVF)
• Increased permeability of the capillaries in the pleura (Inflammation)
• Increased pleural fluid protein level
• Decreased pleural pressure (Lung atelectasis)
• Increased fluid in peritoneal cavity (ascites, PD)
• Disruption of the thoracic duct (iatrogenic, haem malignancy)
• Disruption of thoracic blood vessels (iatrogenic, trauma)
• Obstruction of lymphatics draining parietal pleura (malignancy)
• Elevation of systemic vascular pressures SVCO, RVF)

Question 4

Exudate vs transudate

Answer 4

-Exudate: high protein content (>30g/L)
-Transudate: low protein content (<30g/L)- organ failure, usually bilateral and smaller
-More specifically the Light’s criteria however misclassify 25% transudates as exudates

Question 5

Describe the Light’s criteria

Answer 5

Exudate diagnosed if 2 of:
-Pleural to serum protein ratio >0.5
-Pleural to serum LDH ratio >0.6
-Pleural LDH >2/3 upper limit normal (>145)
IN THE RIGHT CLINICAL CONTEXT

Question 6

Common causes of exudate pleural effusion

Answer 6

-Parapneumonic (pneumonia= increased vocal resonance, bronchial breathing, crackles).
-Malignancy

Question 7

Less common causes of exudate pleural effusion

Answer 7

-Tuberculosis
-PE/infarction
-Rheumatoid arthritis
-SLE
-Pancreatitis
-Benign asbestos
effusion
-Post MI/CABG

Question 8

Very rare causes of exudate pleural effusion

Answer 8

-Yellow nail syndrome
-Drugs (amiodarone, methotrexate)

Question 9

Common causes of transudate pleural effusion

Answer 9

-Heart failure
-Liver failure

Question 10

Less common causes of transudate pleural effusion

Answer 10

-Hypalbuminaemia
-Nephrotic syndrome
-Peritoneal dialysis

Question 11

Very rare causes of transudate pleural effusion

Answer 11

-Hypothyroidism
-Constrictive pericarditis
-Meigs syndrome

Question 12

Investigations of pleural effusions

Answer 12

• Imaging: CXR, USS, CT (PET/MRI experimentally), ECG if chest pain
  -Bloods: FBC, UE, LFT, albumin/calcium, CRP +/- coag screen. Blood cultures if pyrexial, sputum microscopy and culture if productive cough, ABG if low O2
• Pleural aspiration (60ml syringe, green needle, USS): 50ml under USS, ensure not on anticoag, platelet and clotting normal prior
  =If a patient is hypoxic or extremely breathless, then it is sometimes appropriate to
  perform a therapeutic aspiration of around 1L of fluid at the outset
• Appearance/Odour, clarity (srous, haemoserous, heavily blood-stained, purulent, chylous, brown)
  – Biochemistry: total protein, glucose, LDH, pH (10ml)
  – Microbiology: bacteriology (Blood culture bottles),
  AAFB/mycobacterial culture (20ml-60mls)
  – Pathology: cytology (60% sensitivity) 60-200ml, look for inflammatory and malignant cells
• Repeat aspiration?
• Medical thoracoscopy vs VATS

It would be useful to organise a CT with contrast (chest, abdomen and pelvis if malignancy is suspected, or CT
thorax with pleural (venous)-phase contrast if pleural infection is suspected)

Question 13

Pleural effusion on CXR

Answer 13

This demonstrates opacification in the left mid and lower zones.
This is due to a left pleural effusion – the opacification is very dense (completely obscuring both the left heart
border and the left hemi-diaphragm), there is a meniscus at the superior lateral edge and the trachea is
deviated away (tracheal deviation towards the opacification would be more in keeping with lung/lobar
collapse). The presence of a pleural effusion should be confirmed by pleural ultrasound

Question 14

Added diagnostic information of USS

Answer 14

-Echogenic fluid
-Septations
-Pleural thickening
-Pleural/ diaphragmatic nodularity

Question 15

Likely cause of frank pus effusion

Answer 15

Empyema

Question 16

Likely cause of blood-stained effusion

Answer 16

-Malignancy
-Pulmonary infraction
-Post cardiac injury syndrome
-Infection
-TB

Question 17

Likely cause of frank blood effusion

Answer 17

Haemothorax

Question 18

Likely cause of milky effusion

Answer 18

Chylothorax (due to thoracic duct disruption)

Question 19

Likely cause of food particle effusion

Answer 19

Oesophageal rupture

Question 20

Likely cause of bile stained effusion

Answer 20

Biliary fistula (biliothorax)

Question 21

Pleural fluid characteristic tests

Answer 21

-pH (low in pleural infection, RhA, malignancy)
-Protein
-LDH (high malignancy, infection, inflammation)
-Glucose (very low in empyema, RhA)
-Triglycerides (chylothorax: >1.24mmol/L)
-Cholesterol (>5.18mmol/l in pseudochylothorax)
-Haematocrit (blood-stained vs frank blood)
-Amylase (oesophageal rupture, pancreatitis)

Question 22

Low pleural fluid glucose results differentials

Answer 22

parapneumonic effusion/empyema, RA, TB, malignancy,
oesophageal rupture

Question 23

Management of parapneumonic effusion

Answer 23

Simple parapneumonic effusion indicates a reactive process (no bacterial infection within the pleural space
itself) whereas complicated parapneumonic effusion indicates infection within the pleural space and empyema
indicates pus in the pleural space. ‘Pleural infection’ is now the preferred term that encompasses both
empyema and complicated parapneumonic effusion (especially as there might not be a pneumonia present).
pH is the most useful (pus on aspiration or a pH of ≤7.2 are two of the indications for urgent intercostal tube
drainage of an empyema/effusion). pH of >7.2 but <7.4 indicates intermediate risk of pleural infection
(decision to place intercostal drain depends on other factors). It would also be important to ensure that the
patient is on appropriate antibiotic therapy! CT imaging in pleural infection may show an enhancing pleural
margin or gas locules in the fluid. Operative management by the Thoracic surgeons is sometimes required -
either video-assisted thoracoscopic surgery (VATS) or open thoracotomy. Intrapleural fibrinolytic therapy is
sometimes used if the collection of fluid doesn’t fully drain via the ICD

Question 24

Management of malignant pleural effusion

Answer 24

Mesothelioma (also consider invasion of the chest wall/ribs/brachial plexus, or PE).
As well as mesothelioma (by far the most common primary pleural malignancy), lung cancer, breast cancer, GI
and GU cancers, and lymphoma are the most common malignancies affecting the pleura.
Other tests for diagnosing malignant pleural effusion include medical thoracoscopy or CT-guided pleural biopsy
(both done under local anaesthetic) or VATS thoracoscopy (under general anaesthetic).
Procedures to prevent recurrence of a malignant pleural effusion include talc slurry pleurodesis (instillation of
talc via an intercostal drain), talc poudrage done during medical/surgical thoracoscopy or insertion of an
indwelling pleural catheter +/- talc pleurodesis

Question 25

Resources

Answer 25

British Thoracic Society Pleural Disease Guideline (2023) https://thorax.bmj.com/content/78/Suppl_3/s1
Cochrane Review of intrapleural fibrinolytic therapy (2019)
https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD002312.pub4/full?cookiesEnabled