Pleural Disease

Question 1

What is pleural fluid?

Answer 1

Straw-coloured fluid produced by filtration (mainly by the parietal pleura).
Contains some protein and a few cells (macrophages, lymphocytes, mesothelial cells).

Question 2

What is pleural pressure?

Answer 2

Sub-atmospheric.
More negative at the apex, compared to the base.

Question 3

What is a pleural effusion?

Answer 3

A collection of fluid in the pleural space.
Caused by excessive production, reduced absorption (done by pleural lymphatics in the parietal pleura), or both.

Question 4

What are the types of effusion?

Answer 4

Transudate - non-inflammatory, low protein. Occurs due to a problem with filtration.

Exudate - inflammatory, high protein.
A good clinical history and examination will determine the type of effusion.

Question 5

What are the Lights criteria?

Answer 5

Criteria for an exudate effusion.
Protein - pleural fluid : serum fluid > 0.5.
LDH - pleural fluid : serum fluid > 0.6.
Pleural fluid LDH > 2/3rds the upper limit of normal serum LDH.

Question 6

What are the causes of transudates?

Answer 6

Common - LVF, liver cirrhosis.
Less common - hypoalbuminaemia, peritoneal dialysis, hypothyroidism, nephrotic syndrome, mitral stenosis.
Rare - constrictive pericarditis, urinothorax.

Often bilateral, not uncommonly present with subcutaneous oedema or collections of fluid elsewhere in the body. Pulmonary causes are rare.

Question 7

What are the causes of exudates?

Answer 7

Common - malignancy, parapneumonic effusions, empyema, TB.
Less common - pulmonary embolism, asbestos, pancreatitis, post-MI, haemothorax.
Rare - yellow nail syndrome, drugs, fungi.

Question 8

What are the investigations for pleural effusions?

Answer 8

US - sensitive; can mark a site for aspiration; occurs at bedside; assesses pleura.
CXR - accessible; easy to interpret.
CT - visualise pleura in detail; identifies loculations (pockets of fluid or pus); and nodules, lumps, or thickening of the pleura.

Question 9

How is pleural fluid analysed?

Answer 9

Aspiration - simple and safe, done by trained operators.
pH.
Biochemistry - checks protein / LDH / glucose levels to narrow down causes.
Microbiology - cultures fluid for bacteria.
Cytology - checks for abnormal cells.

Question 10

How are pleural effusions managed?

Answer 10

pH < 7.2 with pneumonia, pus or blood - may need a chest drain, as pus may form, making the effusion harder to control.
Transudate - treat the cause, may not need CT.
Exudate - unless the cause is identified, further imaging and biopsies are needed.

Question 11

What is a spontaneous pneumothorax?

Answer 11

Caused by ruptured blebs (weak areas on the surface of the lung) that leak air into the pleural cavity. Air accumulates and compresses the underlying lung.

Primary - in normal lungs.
Secondary - in a person with a pre-existing disease (ILD, COPD, asthma, CF, pleural endometriosis, or genetic disorders).

Question 12

What are the traumatic and iatrogenic causes of pneumothorax?

Answer 12

T - a result of chest injury to the wall.
I - a result of biopsy (from CT guided or US guided; ventilations; inserting a central venous line into large veins of the neck; and pacemakers).

Question 13

What is a tension pneumothorax?

Answer 13

Air in the pleural cavity builds up in pressure and pushes the central structures of the chest. More common with traumatic or iatrogenic causes.
BP and PO2 drops, leading to a cardiorespiratory arrest (requires emergency aspiration).

Question 14

What is the presentation of a pneumothorax?

Answer 14

A sudden event of chest pain or SOB.
Common in tall, thin, young men.
Uncommon in underlying lung disease.
A history of biopsies, line insertions, or mechanical ventilation.

Question 15

What are the results of an examination of a pneumothorax?

Answer 15

Tachypnoeic.
Hypoxic.
Reduced chest wall movement.
Reduced or no breath sounds.
Normal examination - not uncommon.

The size of the pneumothorax depends on the patient’s fitness.

Question 16

What are the investigations of a pneumothorax?

Answer 16

CXR - smaller pneumothoraxes are harder to see, especially in the apices (due to rib shadows).
US - done by an experienced operator, usually in A&E or ITU, if the patient cannot move.
CT - not usually required, but useful in complex examples, underlying severe lung disease, or COPD.

Question 17

What does the management of a pneumothorax depend on?

Answer 17

Size of the pneumothorax.
Effect of the patient (underlying lung disease).
Trained operators and staff in aftercare.

Question 18

What is the management of a pneumothorax?

Answer 18

Watch and wait - in well patients with a small pneumothorax.
Aspiration - in well patients, with a pneumothorax over 2cm in size.
Chest drain insertion - for a large or complex pneumothorax.
Surgery - for recurrent pneumothorax in unresolving cases (do not lift weights or fly for a week to allow healing. Recurrence < 50%).

Question 19

Where is a pleural aspiration done?

Answer 19

In the triangle of safety (2nd intercostal space on the midclavicular line).
Between the lateral border of the pectoral major, the level of the 5th intercostal space, and the border of the latissimus dorsi.

Question 20

What are the types of pleural tumours?

Answer 20

Benign - rare.
Malignant pleural effusions - common.

Question 21

What are malignant pleural effusions?

Answer 21

Associated with a poor outcome.
Secondary malignancies (pleura is involved as a result of usually intra-parenchymal lung cancer) are more common than primary malignancies.
Other common sites - breast, ovarian, renal, thyroid, GI.
Metastases stud the pleural surface or block lymphatics, preventing drainage of pleural fluid.

Question 22

What is mesothelioma?

Answer 22

The most common primary malignancy.
Rare and aggressive.
More common in males.
Occupational (plumbers, electricians, etc.).

Question 23

How is mesothelioma caused?

Answer 23

Inhaled asbestos fibres reach the pleura and cause inflammation, provoking tumour formation.
Latency - 20 to 40 years.
Symptoms - chest pain, SOB, weight loss, clubbed nails (a sign of a pleural effusion).

Question 24

What is the diagnosis of mesothelioma?

Answer 24

CXR - done for pleural effusions or pleural based masses.
Biopsy - needed for staging tissue (done through CT guided, US guided, blind, or thoracoscopy).

Thoracoscopy - directly visualizes the pleura; can spray the lung with sterile talcum powder to try to obliterate the pleural space (pleurodesis) and prevent fluid re-accumulating.

Question 25

What is the management of mesothelioma?

Answer 25

Limited treatment; palliative with poor survival.
Chemotherapy.
Palliative surgery in select patients - mainly in the context of pleurodesis in relatively fit and young patients. Decortication is done (layers of thickened pleura are peeled off, to allow the lung to re-expand. Relieves SOB).