Pleural effusion

Last reviewed: 29 Apr 2023
Last updated: 25 May 2021



History and exam

Key diagnostic factors

  • presence of risk factors
  • dyspnoea
  • dullness to percussion
More key diagnostic factors

Other diagnostic factors

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

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
More risk factors

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
  • protein gradient
  • FBC
  • CRP
  • blood culture
  • sputum Gram stain and culture
  • N-terminal pro-brain natriuretic peptide (NT-pro-BNP) in pleural fluid
More 1st investigations to order

Investigations to consider

  • pleural fluid cholesterol level
  • 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
  • interferon-gamma in pleural fluid and real-time polymerase chain reaction of pleural fluid
More investigations to consider

Emerging tests

  • tumour markers in pleural fluid
  • procalcitonin

Treatment algorithm


congestive heart failure


malignant: poor performance status or limited lifespan (Karnofsky score ≤30% or ECOG score of ≥2)

malignant: good performance status (Karnofsky score >30% or ECOG score of 0 or 1)


persistent empyema despite chest tube

recurrent symptomatic malignant effusions

recurrent benign effusion




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 reviewers

Y.C. Gary Lee, MBChB, PhD, FCCP, FRACP

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.

Clare Hooper, MBBS

Pleural Research Registrar

North Bristol Lung Centre

Southmead Hospital

Westbury on Trym




CH declares that she has no competing interests.

Steven Sahn, MD

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.

  • Pleural effusion images
  • Differentials

    • Pleural thickening
    • Pulmonary collapse and consolidation
    • Elevated hemidiaphragm
    More Differentials
  • Guidelines

    • ACR appropriateness criteria: intensive care unit patients
    • ACR–SIR–SPR practice guideline for specifications and performance of image-guided percutaneous drainage/aspiration of abscesses and fluid collections (PDAFC)
    More Guidelines
  • Patient leaflets

    Pleural effusion

    Chest drain insertion

    More Patient leaflets
  • Videos

    Insertion of intercostal drain, Seldinger technique: animated demonstration

    Insertion of intercostal drain, open technique: animated demonstration

    More videos
  • padlock-lockedLog in or subscribe to access all of BMJ Best Practice

Use of this content is subject to our disclaimer