Last reviewed: 8 Apr 2021
Last updated: 22 Oct 2020



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
  • recent ovarian stimulation treatment
  • 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

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

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

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.


RL received speaking fees provided by Cardinal Health; owned stock in Denver Biomaterials until it was purchased by Cardinal Health; received fees for consulting from Denver Biomaterials; and is an author of of references cited in this topic. CR, PWI, AMC, AD, RJD, and PMG declare that they have no competing interests.

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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