Pleural Fluid Analysis

Question 1

Haemothorax

Answer 1

Exudate

Trauma, malignancy, PE

Question 2

Chylothorax

Answer 2

Transudative or exudative

Leakage from thoracic duct due to lymphoma or thoracic surgical trauma

Question 3

Empyema/ pyothorax (pus)

Answer 3

Exudate with pH less than 7.2

Secondary to pneumonia or abscess

Question 4

Lights criteria

Answer 4

Applied if protein level between 25-35 or if serum protein abnormal

Exudative effusion;

Pleural protein/ serum protein- >0.5
Pleural LDH/ serum LDH- >0.6
Pleural LDH- >2/3 x upper limit of normal serum LDH

Question 5

LDH

Answer 5

Lactate dehydrogenase

Released during tissue damage- makes sense. Exudative the membranes are damaged to allow protein to pass through. Transudative just relies on osmotic force to shift water

Question 6

Glucose in pleural fluid

Answer 6

Normally similar to serum level

Low in MEAT;
Malignancy 
Empyema 
Arthritis (rheumatoid) 
TB

Question 7

Extra tests for pleural fluid

Answer 7

Cell count- lymphocytosis (TB, malignancy)
Culture and sensitivities- identify infectious agents
Cytology- identify malignant causes

Question 8

Hydrothorax

Answer 8

Serous fluid that can be an exudate or a transudate

Question 9

Transudative Effusion

Answer 9

Hydrostatic and oncotic forces cause extravasation of fluid through a normal membrane

Heart failure
Hypoalbuminaemia- liver failure, nephrotic syndrome, malnutrition

<30g/L of protein. Light criteria should be applied if between 25-35

Question 10

Exudative Effusion

Answer 10

Inflammation causes increased permeability of the pleural surface/ capillaries leaking extravascular fluid (including cells, their contents and proteins)

Inflammation
Infection
PE (infarction)
Malignancy

> 30g/L of protein. Light criteria should be applied if between 25-35