Pleural effusion diagnostic study of choice
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Dushka Riaz, MD
Overview
Because the treatment of pleural effusion varies based on the cause it is important to have a good differential diagnosis. This would drive the diagnostic approach and ultimately the diagnostic study of choice based on the presentation. After determining whether the effusion is unilateral or bilateral through chest x-ray, the likely cause should be considered. If the diagnosis is clearly pointing towards nephrotic syndrome or congestive heart failure, then these patients do not necessarily need to have a thoracocentesis performed and should be treated. However, a thoracocentesis becomes the diagnostic study of choice in the following circumstances:
- an unclear cause
- patient experiencing pleuritic chest pain
- patient experiencing symptoms out of proportion to the size of the effusion
- no response to treatment
The use of thoracocentesis becomes urgent if the patient is decompensating or the pleural effusion is considerabley large. [1]
Diagnostic Study of Choice
Study of choice
The diagnostic study of choice is a thoracocentesis that should be performed with a current chest x-ray and under ultrasound guidance. The procedure uses a 21 gauge needle with a 50 mL syringe. After the fluid is removed it is analyzed. Macroscopically the fluid can point to differentials. If milky consider a chylothorax, pus can point to empyema and blood can indicate malignancy. LDH and protein are also measured to determine if the fluid is an exudate or transudate as per Light's Criteria. [1]
The Light's Criteria states that one of three of the following criteria must be met for the fluid to be considered an exudate:
- Pleural fluid protein/serum protein >0.5 or
- Pleural fluid LDH/serum LDH >0.6, or
- Pleural fluid LDH > 2/3 the upper limit of normal.
Exudates are caused by inflammation or impaired lymphatic drainage whereas transudates are caused by changes in the hydrostatic or oncototic pressures. [2]
It is recommended to check pH levels if the cause may be infectious. If the pH levels are less than 7.2 it is advised to drain the fluid immediately to decrease the risk of parapneumonic pleural effusion. Low glucose in the fluid can indicate empyema, tuberculosis, rheumatoid arthritis and malignancy. [1]
References
- ↑ 1.0 1.1 1.2 Jany B, Welte T (2019). "Pleural Effusion in Adults-Etiology, Diagnosis, and Treatment". Dtsch Arztebl Int. 116 (21): 377–386. doi:10.3238/arztebl.2019.0377. PMC 6647819 Check
|pmc=value (help). PMID 31315808. - ↑ Light RW, Macgregor MI, Luchsinger PC, Ball WC (1972). "Pleural effusions: the diagnostic separation of transudates and exudates". Ann Intern Med. 77 (4): 507–13. doi:10.7326/0003-4819-77-4-507. PMID 4642731.