What is the workup for pleural effusion?

From the Guidelines

The workup for plural effusion should begin with a thorough history and physical examination, followed by thoracic ultrasound (TUS) to assess the size and character of the effusion, and then diagnostic thoracentesis to analyze the fluid, as recommended by the British Thoracic Society guideline for pleural disease 1. The initial evaluation should include a careful history and physical examination to elucidate the likely cause of the pleural effusion, and a drug history should always be recorded, as certain medications can cause exudative pleural effusions 1. Key points to consider in the workup of plural effusion include:

• The use of TUS as a diagnostic tool and to improve the safety of invasive procedures 1
• The classification of the effusion as transudative or exudative using Light's criteria, with exudates suggesting localized pleural pathology such as infection, malignancy, or inflammation 1
• The importance of prompt diagnosis to aid in patient management, particularly in cases of exudative effusions 1
• The use of chest CT as the reference standard for imaging, particularly if malignancy is suspected or if the effusion is too small to sample 1 A systematic approach to investigation is necessary to establish a diagnosis swiftly, while minimizing unnecessary invasive investigations, and to facilitate treatment 1. Additional tests should be guided by clinical suspicion, and management should target the underlying cause while providing symptomatic relief through therapeutic thoracentesis if the effusion is large or causing respiratory distress.

From the Research

Plural Effusion Workup

• The diagnostic evaluation of pleural effusion includes chemical and microbiological studies, as well as cytological analysis, which can provide further information about the etiology of the disease process 2.
• Pleural fluid puncture (pleural tap) enables the differentiation of a transudate from an exudate, which remains the foundation of the further diagnostic work-up 3.
• The patient's history and physical examination should guide evaluation, and small bilateral effusions in patients with decompensated heart failure, cirrhosis, or kidney failure are likely transudative and do not require diagnostic thoracentesis 4.
• Multiple guidelines recommend early use of point-of-care ultrasound in addition to chest radiography to evaluate the pleural space, and chest radiography is helpful in determining laterality and detecting moderate to large pleural effusions 4.
• Computed tomography of the chest can exclude other causes of dyspnea and suggest complicated parapneumonic or malignant effusion, and pleural aspirate should routinely be evaluated using Gram stain, cell count with differential, culture, cytology, protein, l-lactate dehydrogenase, and pH levels 4.

Diagnostic Tests

• Light's criteria can help differentiate exudates from transudates, and additional assessments should be individualized, such as tuberculosis testing in high-prevalence regions 4.
• The combination of CT plus pleural fluid cytology (PFC) significantly improved sensitivity and accuracy in distinguishing between benign and malignant pleural effusion 5.
• CT and PFC used together may lead to approximately 100% specificity and >90% sensitivity in distinguishing between benign and malignant PE 5.

Treatment

• Transudative effusions are usually managed by treating the underlying medical disorder, and a large, refractory pleural effusion, whether a transudate or exudate, must be drained to provide symptomatic relief 2.
• Management of exudative effusion depends on the underlying etiology of the effusion, and malignant effusions are usually drained to palliate symptoms and may require pleurodesis to prevent recurrence 2, 3.
• The proper treatment of pleural effusion can be determined only after meticulous differential diagnosis, and the range of therapeutic options has recently become much wider 3.