Pleural effusion is defined as the accumulation of excess fluid in the pleural space, the cavity located between the parietal and visceral pleura of the lungs. This condition can compromise respiratory mechanics and introduces both diagnostic and therapeutic challenges in clinical practice, especially in primary care settings. Pleural effusions are commonly categorized as transudative or exudative based on the pleural fluid’s biochemical properties, with diagnostic thoracentesis serving as a key procedure to determine etiology and guide treatment (Panjwani & Salman, 2019; Brahmbhatt et al., 2024).

Image credit https://en.wikipedia.org/wiki/Pleural_effusion

In the accompanying diagram above , each component of the thoracic anatomy is labeled to illustrate how pleural fluid builds up and creates a pleural effusion:

1. Trachea: Shown in the center at the top, the trachea conducts air from the upper airway down to the lungs.

2. Lung: Represented in gray and enclosed by the pleural membranes. It requires adequate space to expand during breathing.

3. Pleura : The pleura is a two-layered membrane—one layer (the visceral pleura) tightly coats the lung surface, and the other layer (the parietal pleura) lines the inside of the chest wall.

4. 
   

5. Pleural Effusion: Indicated in yellow, this fluid accumulates in the potential space between the visceral and parietal pleura.

When excessive fluid accumulates, it can compress the lung, reducing its capacity to expand fully. This compromised lung expansion may lead to symptoms such as shortness of breath and discomfort. Clinicians often use diagnostic thoracentesis—a procedure to draw fluid from this pleural space—to analyze the fluid and determine the underlying cause (e.g., heart failure, infection, or malignancy).

Type of Effusion	Common Causes	Underlying Mechanism
Transudative	- Congestive Heart Failure (CHF) - Cirrhosis (hepatic hydrothorax) - Nephrotic Syndrome - Hypoalbuminemia (various causes) - Peritoneal Dialysis - Atelectasis (in some cases)	Primarily due to systemic factors that alter hydrostatic (↑) and/or oncotic (↓) pressures. For instance, in CHF, elevated (↑) hydrostatic pressure in the pulmonary capillaries leads to fluid accumulation; in cirrhosis or nephrotic syndrome, low (↓) oncotic pressure (e.g., from decreased albumin) promotes fluid leakage.
Exudative	- Parapneumonic effusions (bacterial pneumonia) - Malignancy (lung cancer, breast cancer, lymphoma, etc.) - Tuberculosis - Pulmonary Infarction (pulmonary embolism) - Pancreatitis (particularly if severe) - Connective Tissue Diseases (rheumatoid arthritis, SLE) - Chylothorax (thoracic duct injury) - Hemothorax (trauma, vessel rupture)	Usually result from local factors that increase (↑) pleural membrane permeability, decrease (↓) lymphatic drainage, or cause direct injury/inflammation to the pleura. Infections, malignancy, and inflammatory conditions often provoke an inflammatory response, altering the normal pleural fluid dynamics and allowing proteins/cells to leak into the pleural space.

Typical clinical examination findings in a patient with a suspected pleural effusion include:

1. Dullness to Percussion: Tapping on the chest wall over the fluid-filled area often produces a flat or dull sound instead of the normal resonant note.

2. Decreased or Absent Breath Sounds: Fluid in the pleural space insulates and dampens the transmission of breath sounds, leading to reduced or nearly inaudible sounds over the effusion.

3. Reduced Tactile Fremitus: When the patient speaks, the vibration felt on the chest wall is diminished due to fluid interrupting transmission from the lungs.

4. Egophony at Upper Margin: At times, just above the level of the fluid, the patient’s spoken “E” may be heard as an “A” (known as egophony), though this finding may be subtle.

5. Decreased Chest Expansion: On the side with the effusion, the chest may expand less during inspiration.

FLOWCHART: MANAGEMENT OF PLEURAL EFFUSION IN PRIMARY CARE
(Based on BTS [2010], NICE, and Clinical Guidelines)
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1. PATIENT PRESENTATION
- Common Symptoms: Dyspnea, cough, pleuritic chest pain, reduced exercise tolerance

↓

2. HISTORY & PHYSICAL EXAM
- Relevant History:
• Cardiac disease (CHF)
• Malignancy or previous cancer
• Recent infection (pneumonia, TB risk factors)
• Liver/kidney disease (cirrhosis, nephrotic syndrome)
- Physical Findings:
• Dull percussion
• Reduced or absent breath sounds
• Possible tracheal deviation (if large effusion)
• Peripheral edema, raised JVP (if CHF)

↓

3. INITIAL IMAGING
- Obtain Chest X-ray (PA/lateral) to confirm fluid
- If uncertainty persists or small effusion suspected:
• Consider ultrasound
• Lateral decubitus film (to differentiate fluid vs. consolidation)

↓

4. EFFUSION CONFIRMED?
- NO → Investigate other causes (e.g., pneumonia, COPD, other lung pathology)
- YES → Proceed to further assessment

↓

5. ASSESS LIKELY CAUSE
- Transudative Clues:
• Bilateral effusions
• Elevated JVP, peripheral edema (CHF)
• Hypoalbuminemia, liver/kidney disease
- Exudative Clues:
• Unilateral effusion
• Fever, night sweats, weight loss
• History of malignancy
• Pleuritic chest pain
• Possible infection signs (e.g., pneumonia)

↓

Classification of Pleural Effusions by Laterality

Bilateral Pleural Effusions

Unilateral Pleural Effusions

More Likely Transudative (≈80%): Common Systemic Causes • Congestive Heart Failure (CHF)  - Often accompanied by elevated jugular venous pressure (JVP), peripheral edema,    and cardiomegaly on chest X-ray. • Cirrhosis (Hepatic Hydrothorax)  - Typically right-sided but can be bilateral; frequently associated with ascites. • Nephrotic Syndrome  - Hypoalbuminemia (<3 g/dL) and proteinuria lead to reduced oncotic pressure. Less Common Exudative Causes (≈20%): • Autoimmune diseases (e.g., Systemic Lupus Erythematosus or Rheumatoid Pleurisy) • Rare: Metastatic Malignancy, Tuberculosis (TB), or Post-cardiac Injury Syndrome

More Likely Exudative (≈80%): Key Causes • Infection (Parapneumonic effusion / Empyema)  - Often presents with fever, elevated inflammatory markers (e.g., CRP),    and consolidation on imaging. • Malignancy (Lung cancer, Mesothelioma, Metastatic disease)  - May have weight loss, history of smoking, or known primary cancer;    often requires cytological analysis of pleural fluid. • Pulmonary Embolism (PE)  - Sudden-onset pleuritic chest pain, dyspnea, hypoxia; D-dimer and CTPA may be diagnostic. • Tuberculosis (TB)  - Night sweats, prolonged cough, risk factors for TB exposure, positive tuberculin test. Less Common Transudative Causes (≈20%): • Hepatic Hydrothorax  - May occur in cirrhosis and typically manifests on the right side. • Urinothorax  - Rare; secondary to urinary tract obstruction or trauma, leading to urine in the pleural space.

Note: While this laterality-based classification provides helpful clues, definitive diagnosis still relies on pleural fluid analysis (e.g., Light’s criteria) and correlation with clinical, laboratory, and imaging findings. ( Light’s criteria are used to distinguish exudative pleural effusions from transudative ones by comparing certain ratios of pleural fluid to blood values )

• "If bilateral, check for CHF (BNP), hypoalbuminemia, or cirrhosis. If unilateral, prioritize exudative workup (CRP, sputum, malignancy screen)."

6. INITIAL TESTS
- Bloodwork:
• BNP (if CHF suspected)
• CBC, CRP
• LFTs, renal function, albumin
- Consider:
• D-dimer (if pulmonary embolism suspected)
• Sputum culture (if infection likely)

↓

7. TRANSUDATIVE SUSPICION?
- YES:
• Treat the Underlying Cause:
- CHF: Diuretics, sodium restriction, optimize cardiac medications
- Hypoalbuminemia: Treat liver/kidney disease, ensure nutritional support
• Monitor:
- Repeat chest X-ray in 1–2 weeks
- Assess clinical improvement
• Improvement?
- YES: Continue management
- NO: Refer to respiratory specialist for further evaluation

- NO or UNCERTAIN → See Step 8

↓

8. EXUDATIVE SUSPECTED OR UNCERTAIN
- Are RED FLAGS present? (fever, weight loss, hypoxia, severe dyspnea, large effusion)
• YES → Urgent referral to secondary care:
- Diagnostic thoracentesis (fluid analysis: pH, protein, LDH, cytology, culture)
- Possible CT chest
- Therapeutic drainage if symptomatic
• NO → Routine referral for pleural fluid analysis and further imaging

↓

9. INFECTION SUSPECTED?
- YES:
• Start empiric antibiotics (e.g., amoxicillin-clavulanate) if bacterial infection is likely
• Urgent specialist referral if complicated effusion (empyema or parapneumonic effusion)
• Drainage if indicated (e.g., large or purulent collection)

↓

10. MALIGNANCY SUSPECTED?
- YES:
• Urgent oncology referral
• Consider pleural biopsy or further imaging (CT, PET-CT)
• Therapeutic drainage for symptomatic relief

↓

11. MONITORING & FOLLOW-UP
- Small or Asymptomatic Effusions:
• Repeat chest X-ray in 4–6 weeks
- Persistent or Recurrent Effusions:
• Refer to respiratory specialist for reassessment (thoracentesis, pleurodesis consideration, etc.)

Management of pleural effusion in primary care emphasizes early diagnosis and prompt symptom relief. Initial assessment often includes physical examination, imaging studies, and possibly point-of-care ultrasound to evaluate the size and characteristics of the effusion (DeBiasi et al., 2015; Cotton et al., 2018). When indicated, thoracentesis serves both a diagnostic and therapeutic role, allowing for fluid analysis and relief of respiratory distress, and potentially informing further treatment strategies, especially in cases of malignancy or infection (Panjwani & Salman, 2019; Rendón-Ramírez et al., 2024).

Given the varied presentations and underlying causes, a tailored approach is paramount. For example, while palliative measures may be appropriate for patients with malignant pleural effusions, others might benefit from more aggressive interventions, including the placement of indwelling pleural catheters for recurrent effusions (Saqib et al., 2017; Sivagnaname et al., 2022). Essential supportive measures, such as oxygen therapy and management of any underlying conditions, further complement specific interventions for pleural effusion (Brahmbhatt et al., 2024; Bae et al., 2010).

In conclusion, pleural effusion presents a critical aspect of patient care in primary settings, necessitating a thorough understanding of its diverse etiologies and management strategies. Early intervention and carefully tailored treatment protocols can significantly impact patient outcomes, underscoring the importance of clinician awareness and timely management of this condition.

Disclaimer: The content provided here is meant solely as a reference point for clinicians and is not a validated guideline. It represents an effort to address the topic of pleural effusion management and offer primary care clinicians an anchoring framework to help recognize and evaluate this condition. Clinicians should always use their professional judgment, consider individual patient circumstances, and refer to local or specialist guidelines to ensure safe and effective patient care.

References

(2013). Current management of pleural disorders. Current Research in Medicine, 4(1), 110-121. https://doi.org/10.3844/amjsp.2013.110.121

Bae, S., Hwang, J., Kim, W., Yoon, H., Kim, J., Nam, Y., … & Kim, Y. (2010). A case of cardiac amyloidosis with diuretic-refractory pleural effusions treated with bevacizumab. Korean Circulation Journal, 40(12), 671. https://doi.org/10.4070/kcj.2010.40.12.671

Blayney, M., Nguyen, A., & Aboulafia, D. (2016). Diagnosis and management of a pancreaticopleural fistula in a patient with aids and a large pleural effusion. Journal of the International Association of Providers of Aids Care (Jiapac), 15(6), 459-462. https://doi.org/10.1177/2325957416668578

Brahmbhatt, H., Nanda, T., & Prabhu, P. (2024). Pleural effusion during tyrosine-kinase inhibitor (imatinib) treatment in chronic myeloid leukemia - a case report. Journal of Biomedical and Pharmaceutical Research, 13(4), 29-34. https://doi.org/10.32553/jbpr.v13i4.1117

BTS (2010). British Thoracic Society. Guidelines for the Investigation of a Unilateral Pleural Effusion in Adults. Thorax, 65(Suppl 2), ii4-ii17.

Clinical Practice Guidelines. Various authors. Clinical guidelines for the management of pleural effusions. (No specific publication details provided.)

Cotton, D., Lenz, R., Kerr, B., & Irene, W. (2018). Point of care ultrasound for the general internist: pleural effusions. Canadian Journal of General Internal Medicine, 13(2), 24-29. https://doi.org/10.22374/cjgim.v13i2.231

DeBiasi, E., Pisani, M., Murphy, T., Araujo, K., Kookoolis, A., Argento, A., … & Puchalski, J. (2015). Mortality among patients with pleural effusion undergoing thoracentesis. European Respiratory Journal, 46(2), 495-502. https://doi.org/10.1183/09031936.00217114

NICE. National Institute for Health and Care Excellence. Guidance on pleural effusions. 

Panjwani, A., & Salman, M. (2019). An uncommon cause of pleural effusion. Breathe, 15(2), e84-e89. https://doi.org/10.1183/20734735.0365-2018

Rendón-Ramírez, E., Morales-García, A., Rendón, A., Náñez-Terreros, H., Solís, R., Magaña-García, A., … & Porcel, J. (2024). Pleural effusion identified by point of care ultrasound (pocus) in septic shock: impact on clinical outcomes. Pocus Journal, 9(2), 55-61. https://doi.org/10.24908/pocus.v9i2.17293

Saqib, I., Iqbal, M., Rana, A., & Hassan, S. (2017). Experience with ambulatory management of pleural pathologies utilizing small-bore indwelling pleural catheters. Cureus. https://doi.org/10.7759/cureus.1636

Singh, A., Aggarwal, S., Sood, N., Selhi, P., Singh, A., & Resident, S. (2020). Malignant pleural effusions with unknown primary sites: a 6 years cytological study. Indian Journal of Pathology and Oncology, 5(3), 450-453. https://doi.org/10.18231/2394-6792.2018.0087

Sivagnaname, Y., Krishnamurthy, D., Radhakrishnan, P., & Selvam, A. (2022). Indwelling pleural catheters. https://doi.org/10.5772/intechopen.100645

Yang, T., Hsia, D., & Chang, D. (2018). Patient- and hospital-level factors associated with readmission for malignant pleural effusion. Journal of Oncology Practice, 14(9), e547-e556. https://doi.org/10.1200/jop.18.00201