Approach to Pleural Effusions

Case Presentation: A Puzzling Pleural Effusion

This week in #AMReport at @WCHospital (#WCHMorningReport) we reviewed a diagnostic approach to pleural effusions. We discussed a case of a young woman who had recently  immigrated to Canada from Asia and presented to hospital with 6 weeks of constitutional symptoms and dyspnea on exertion. She was found to have a large right-sided pleural effusion.  A thoracentesis surprisingly revealed a chylothorax and she was eventually diagnosed with lymphoma.

Approach to Pleural Effusions

Infographic from The Intern at Work
Check out their Podcast on Pleural Effusions entitled Pockets of Fluid- Pleural Effusion!

How to Perform a Thoracentesis

Check out this website that is an interactive, step by step guide to guide you through everything from the consent process to the clean up.  Check it out before your next thoracentesis:

Light’s Criteria

Just remember “5-6-7”

  • Pleural protein/serum protein >0.5
  • Pleural LDH/serum LDH >0.6
  • Pleural LDH >2/3 the ULN of serum LDH

JAMA Rational Clinical Exam

  • An exudative effusion is most likely if:
    • Cholesterol level >55 mg/dL (+LR 7.1-250)
    • LDH >200 (+LR 18)
    • Pleural cholesterol/serum cholesterol >0.3 (+LR 14)
      • From a Choosing Wisely perspective, I would not recommend ordering pleural cholesterol levels on most patients, however!
  •  Exudate is much less likely when all of Light’s criteria are absent (-LR 0.04)

What to Do with an Exudate NYD?

  • If cytology is negative, can repeat thoracentesis once for increased sensitivity. The sensitivity of pleural fluid cytology for malignancy is only 60-70% and the diagnostic yield after 2 samples is extremely low.
  • Ger a CT of the chest (as recommended by the British Thoracic Society guideline to guide further diagnostic testing). However, the absence of abnormalities does not exclude malignant disease. But a CT may help guide the next steps in your diagnostic process.
    • A retrospective study of patients with undiagnosed effusions demonstrated that the sensitivity and specificity of the CT scan for malignant disease were 68% and 78%, respectively.
  • Refer for pleural biopsy. This may be done CT- or ultrasound-guided if there is a clear abnormality, but thorascopy with pleural biopsy is the preferred test.


  • A chylothorax is an effusion from lymphatic fluid in the pleural space. It is defined by the presence of elevated triglycerides (>1.24 mmol) and chylomicrons
  • The most common cause of non-traumatic chylothorax is malignancy, specifically lymphoma followed by bronchogenic carcinoma and other malignancies such as breast cancer.
  • Other causes include TB, trauma, filariasis, amyloidosis, sarcoidosis and LAM

Additional Reading

  1. JAMA Rational Clinical Exam: Does This Patient Have an Exudative Pleural Effusion?
  2. Evaluation of the patient with pleural effusion. CMAJ March 2018
  3. Management of Malignant Pleural Effusions. An Official ATS/STS/STR Clinical Practice Guideline

Leave a Reply