What is the diagnostic workup for a left pleural effusion?

From the Guidelines

The workup for a left pleural effusion should begin with a careful history and physical examination, followed by thoracic ultrasound (TUS) to assess the size and character of the effusion, as recommended by the British Thoracic Society guideline for pleural disease 1. The initial evaluation should include a detailed occupational history, including any previous asbestos exposure, and a thorough review of the patient's drug history, as certain medications can cause exudative pleural effusions 1. Key points to consider in the workup include:

• The use of TUS as a diagnostic tool and to improve the safety of invasive procedures 1
• The importance of determining the size and character of the effusion to guide further investigations 1
• The need to consider malignancy as a potential cause, particularly if signs of malignancy such as nodularity of the diaphragm and parietal pleural are present on TUS 1
• The use of CT scan with contrast to evaluate for underlying lung pathology, masses, or lymphadenopathy if malignancy is suspected or if it is not safe to proceed with a pleural aspiration 1 Additional imaging studies, such as chest X-ray, may be necessary to detect larger effusions, but TUS is more sensitive for detecting smaller effusions 1. If a firm diagnosis cannot be made, it may be sensible to reconsider diagnoses with a specific treatment, such as tuberculosis, pulmonary embolism, or lymphoma, and to consider watchful waiting with interval CT scans 1. The underlying cause of the pleural effusion will determine the treatment, which may include antibiotics, diuretics, or pleurodesis, and serial thoracentesis or chest tube placement may be needed for symptom relief in large effusions causing respiratory compromise 1.

From the Research

Workup for Left Pleural Effusion

The workup for left pleural effusion involves several steps to determine the underlying cause of the effusion.

• The first step is to perform thoracocentesis to obtain pleural fluid for analysis 2, 3, 4, 5.
• The pleural fluid is then analyzed to distinguish between transudative and exudative effusions using Light's criteria, which measures the concentrations of protein and lactate dehydrogenase (LDH) in the pleural fluid and serum 2.
• If the effusion is transudative, therapy should be directed toward the underlying congestive heart failure, cirrhosis, or nephrosis 2.
• If the effusion is exudative, attempts should be made to define the etiology, which may include pleural fluid cytology, adenosine deaminase and gamma-interferon levels, and thoracoscopy 2, 3, 4.
• The diagnosis of pleural malignancy is most easily established via pleural fluid cytology, and if this is negative, thoracoscopy is indicated 2.
• Pleural biopsy is recommended for evaluation and exclusion of various etiologies, such as tuberculosis or malignant disease 3, 4.
• In cases of pneumonia and pleural effusion, therapeutic thoracentesis should be performed, and the pleural fluid should be Gram-stained and cultured 2.
• The use of biomarkers such as procalcitonin (PCT) in pleural fluid may help distinguish infectious from noninfectious etiologies of pleural effusions 6.
• A systematic approach is needed to enable a rapid diagnosis and an appropriate treatment, and further analysis of the pleural fluid or thoracic imaging or pleural biopsy may be necessary 5.

Key Tests and Procedures

• Thoracocentesis 2, 3, 4, 5
• Pleural fluid analysis (protein, LDH, adenosine deaminase, gamma-interferon, cytology) 2, 3, 4
• Light's criteria 2
• Pleural biopsy 3, 4
• Thoracoscopy 2, 3, 4
• Procalcitonin (PCT) levels in pleural fluid 6

Etiologies and Management

• Transudative effusions: managed by treating the underlying medical disorder (congestive heart failure, cirrhosis, nephrosis) 2, 3, 4
• Exudative effusions: management depends on the underlying etiology (malignancy, infection, pulmonary embolism) 2, 3, 4
• Malignant effusions: drained to palliate symptoms and may require pleurodesis to prevent recurrence 2, 3, 4
• Empyemas: treated with antibiotics and intercostal drainage, and may require surgery in selected cases 3