Last reviewed:September 2019
Last updated:February  2019



History and exam

Key diagnostic factors

  • presence of risk factors
  • dyspnoea
  • dullness to percussion

Other diagnostic factors

  • pleuritic chest pain
  • cough
  • quieter breath sounds
  • decreased or absent tactile fremitus

Risk factors

  • congestive heart failure
  • pneumonia
  • malignancy
  • pulmonary embolism
  • recent coronary artery bypass graft surgery
  • recent myocardial infarction
  • occupational lung disease
  • rheumatoid arthritis
  • systemic lupus erythematosus
  • renal failure
  • drug-induced pleural effusion
  • chylothorax

Diagnostic investigations

1st investigations to order

  • postero-anterior and lateral chest x-ray
  • pleural ultrasound
  • LDH and protein in pleural fluid and serum
  • red blood cell count in pleural fluid
  • WBC count and differential of pleural fluid
  • cytology of pleural fluid
  • culture of pleural fluid
  • pH of pleural fluid
  • glucose in pleural fluid
  • pleural fluid cholesterol level
  • protein gradient
  • FBC
  • CRP
  • blood culture
  • sputum Gram stain and culture
  • N-terminal pro-brain natriuretic peptide (NT-pro-BNP) in pleural fluid
Full details

Investigations to consider

  • thoracic CT scan
  • thoracic MRI
  • helical CT scan
  • amylase in pleural fluid
  • adenosine deaminase (ADA) level in pleural fluid
  • lipid analysis of pleural fluid
  • thoracoscopy
  • bronchoscopy
  • pleural biopsy
Full details

Emerging tests

  • tumour markers in pleural fluid
  • interferon-gamma in pleural fluid and real-time polymerase chain reaction of pleural fluid
  • soluble triggering factor expressed on myeloid cells
  • procalcitonin
Full details

Treatment algorithm


Consultant Respiratory Physician

Chelsea and Westminster Hospital NHS Foundation Trust




OO declares that he has no competing interests.

Dr Orhan Orhan would like to gratefully acknowledge Drs Clare Ross, Philip W. Ind, Anob M. Chakrabarti, Richard Light, Amber Degryse, Rachel J. Davies, and Peter M. George, previous contributors to this topic.

Peer reviewersVIEW ALL

Consultant Chest Physician and Senior Lecturer

Oxford Centre for Respiratory Medicine and University of Oxford Churchill Hospital




YCGL declares that he has no competing interests.

Pleural Research Registrar

North Bristol Lung Centre

Southmead Hospital

Westbury on Trym




CH declares that she has no competing interests.

Professor of Medicine and Director

Division of Pulmonary/Critical Care/Allergy/Sleep Medicine

Medical University of South Carolina




SS declares that he has no competing interests.

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