Pleural Effusion

This one is more of a presentation of different diseases, rather than a disease itself.

Pleural Effusion

Definition: fluid accumulation in the pleural space.

Blood in the pleural space = haemothorax

Pus in the pleural space = empyema

Chyle (lymph with fat) = chylothorax


A pleural effusion can be classified as either a transudate or exudate.

Transudate = low protein content ( <25g/L)

May be due to increased venous pressure or hypoproteinaemia (reduced oncotic pressure).

Causes: Remember the failures– heart failure, kidney failure, liver failure (cirrhosis)

   Also- constrictive pericarditis, fluid overload states, malabsorption, nephrotic syndrome

           – hypothyroidism and Meigs’ syndrome ( = right pleural effusion + ovarian fibroma)

-Transudates tend to be bilateral because it’s usually a systemic problem causing it.

Exudate = high protein content (> 35g/L)

Mostly due to increased leakiness of pleural capillaries secondary to infection, inflammation or malignancy.

Causes: pneumonia (termed parapneumonic effusion, unless it’s an empyema), TB, pulmonary infarction, rheumatoid arthritis (RA), SLE, sarcoidosis, acute pancreatitis, bronchogenic carcinoma, malignant metastasis, lymphoma, mesothelioma, lymphangitis carcinomatosis, oesophageal carcinoma, post-MI

-Exudates are often unilateral.

So, what about in between 25 and 35g/L?

Just guess

or… Light’s Criteria.

Light’s criteria:

The fluid is an exudate if any of the following applies:

-Pleural fluid protein/serum protein >0.5

-Pleural fluid LDH/ serum LDH >0.6

-Pleural fluid LDH > 2/3rds the upper limit of normal serum LDH


-can be asymptomatic OR


-pleuritic chest pain

-symptoms of cause


-decreased chest expansion

-over area of effusion:

   -reduced breath sounds

   -stony dull percussion note

(apparently some people have magic ears and can note a difference between dull and stony dull)

   -reduced vocal resonance and tactile vocal fremitus

-above the effusion, where lung is compressed, there may be bronchial breathing

-with large effusions, there may be tracheal deviation away from the effusion

-may see aspiration marks (from previous aspiration)

-signs of associated disease:

e.g. malignancy- cachexia, clubbing, lymphadenopathy, radiation marks, mastectomy scar

stigmata of chronic liver disease- spider naevi, telangiectasia, palmar erythema, gynaecomastia

rheumatoid arthritis- joint deformities

SLE-butterfly rash


-Chest x-ray: visualise effusion, seen as homogenous opacification

    small effusions = blunting of costophrenic angles

Image result for chest x-ray small pleural effusion

     large effusions = water-dense shadows with concave upper borders- meniscus

     (a completely flat horizontal upper border implies that there is also a pneumothorax)

Image result for chest x-ray pleural effusion

Ultrasound– useful in identifying the presence of pleural fluid and in guiding diagnostic or therapeutic aspiration

Diagnostic aspiration/tap:

Turbid, yellow fluid may be due to empyema or Para pneumonic effusion.

Haemorrhagic fluid may be due to trauma, malignancy or pulmonary infarction.

Send fluid off for: Clinical chemistry, Microbiology, Cytology, Immunology

Clinical chemistry =


Glucose– < 3.3 mmol/L in empyema, malignancy, TB, RA, SLE

pH<7.2 in empyema, malignancy, TB, RA, SLE

LDH- ↑ (pleural : serum >0.6) in empyema, malignancy, TB, RA, SLE

Amylase– ↑ in pancreatitis, carcinoma, bacterial pneumonia, oesophageal rupture

Microbiology =

Microscopy and culture

Auramine stain (for TB)

TB culture

Cytology = look for malignant cells

Neutrophils ↑- parapneumonic effusion, PE

Lymphocytes ↑- malignancy, TB, RA, SLE, sarcoidosis

Mesothelial cells- pulmonary infarct

Abnormal mesothelial cells- mesothelioma

Multinucleated giant cells- rheumatoid arthritis

Lupus erythematosus cells- SLE

Immunology (if indicated) =

Rheumatoid factor- rheumatoid arthritis


Complement- reduced in RA, SLE, malignancy, infection

Pleural biopsy: if pleural analysis is inconclusive, consider parietal pleural biopsy. Thoracoscopic or CT-guided pleural biopsy increases diagnostic yield.


-Manage the underlying cause

Drainage: if symptomatic, drain the effusion, repeatedly, if required. This can be by aspiration or with an intercostal drain.

Pleurodesis: sticking the two pleural layers together, obliterating the pleural space, with tetracycline, bleomycin or talc may be helpful for recurrent effusions.

Thoracoscopic talc pleurodesis is most effective for malignant effusions.

Empyemas are best drained using a chest drain, inserted under USS or CT guidance.

Surgery- required if persistent collections and increasing pleural thickness

References: Cheese & Onion, Oxford Clinical Cases of Medicine & Surgery

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