Pleural Aspiration – Pleural effusions

Last Updated on by frcemuser


  • diagnostic (to determine the cause of a pleural effusion)
  • therapeutic (to relieve symptoms of dyspnoea).


  • Local skin infection
  • Uncooperative patient
  • Uncorrected bleeding diathesis – Deranged INR (ideally INR should be less than 1.5).
  • Relative contraindication with bullous lung disease and small effusions


  • Mark the optimal site for aspiration, on the posterolateral aspect of the chest wall (midscapular or posterior axillary line), 1–2 intercostal spaces below the percussed upper border of the effusion.
  • Ensure the proposed site is directly over a palpable intercostal space and above the level of the diaphragm (no lower than the 8th intercostal space).
  • Note: If the effusion is poorly defined clinically do not proceed; request USS to mark the effusion.


  • Pneumothorax—Intercostal drain insertion may be necessary.
  • Bleeding—Apply direct pressure.
  • Spleen or liver puncture—Request an ultrasound of the chest with marking of the site for aspiration if the fluid is difficult to detect.
  • Costal neurovascular bundle damage: The chances of penetrating this bundle can be minimised by always inserting the needle over the upper border of a rib

Pleural effusions – clinical assessment

There are many causes of pleural effusions and they are commonly classified into transudates and exudates

Causes of transudate pleural effusions ((protein < 30 g/L)

  • Heart failure
  • Cirrhosis
  • Hypoalbuminaemia
  • Peritoneal dialysis
  • Hypothyroidism
  • Nephrotic syndrome
  • Mitral stenosis

Causes of exudative pleural effusions (protein > 30 g/L)

  • Pneumonia
  • Malignancy (most commonly lung cancer in men and breast cancer in women)
  • Pulmonary embolism (80% exudates, 20% transudates)
  • Autoimmune disease (especially rheumatoid arthritis)
  • Asbestos exposure
  • Pancreatitis
  • Dressler’s syndrome (following AMI)
  • Tuberculosis

Pleural fluid laboratory analysis

  • A transudate contains less than 25 g/l of protein
  • An exudate contains more than 35 g/l of protein
  • If the pleural fluid contains protein at levels between 25 g/l and 35 g/l then Lights Criteria should be used to decide whether the effusion is a transudate or an exudate
  • Lights criteria state that the fluid is an exudate if one or more of the following criteria are met:
    • Pleural fluid : Serum protein ratio is greater than 0.5
    • Pleural fluid LDH : Serum LDH is greater than 0.6
    • Pleural fluid LDH is greater than two thirds the upper limit of normal serum LDH.

Further tests

If exudate is confirmed, further testing required to evaluate the cause of exudate

  • Differential cell count (predominance of white cells)
  • Gram stain and culture and cytology
  • Glucose
  • LDH level – This is classically high in exudates
  • Pleural fluid pH (Low glucose and pH = infection or malignancy)
  • Amylase

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