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Pleural Effusion

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Pleural Effusion is an abnormal fluid accumulation in the pleural cavity, classified as a pleural disease. Under normal circumstances, the pleural cavity contains only a tiny amount of fluid (10-20 mL) to facilitate smooth pleural movement. When the fluid volume increases, it can compress lung tissue, leading to symptoms such as shortness of breath, chest pain, and other respiratory issues. Prompt diagnosis and treatment are essential.

Symptoms

The severity of symptoms associated with pleural effusion depends on the volume of fluid, the speed of accumulation, and the underlying cause.

Shortness of Breath: Caused by fluid compressing the lungs, restricting lung expansion.
Chest Pain: Typically sharp or stabbing, worsened by deep breathing or coughing.
Dry Cough: Usually non-productive, without significant sputum.
Systemic Symptoms: Fever and chills (indicative of infectious effusion).
Fatigue and Loss of Appetite: Common in effusion related to tumours or chronic illnesses.

Causes and Factors

（1）Infection-Related Causes

Tuberculosis: A common cause of exudative effusion, particularly in high-prevalence areas like Hong Kong.
Bacterial Pleural Infection: Associated with conditions such as pneumonia.

（2）Tumour-Related Causes

Lung Cancer and Breast Cancer: Frequently cause malignant pleural effusion.
Pleural Metastases or Primary Mesothelioma: Tumour involvement of the pleura.

（3）Cardiovascular and Endocrine Diseases

Heart Failure: Elevated venous pressure leads to transudative fluid accumulation in the pleural space.
Liver Cirrhosis: Ascitic fluid may pass through the diaphragm into the pleural cavity.
Renal Failure: Hypoproteinaemia contributes to increased pleural fluid leakage.

（4）Other Causes

Trauma: Chest injuries may cause blood or fluid accumulation in the pleural space.
Pancreatitis: This can lead to pleuritis and associated effusion.

Classification of Pleural Effusion

Pleural Effusion is primarily classified into two categories based on the nature of the fluid and its underlying cause:

Exudative Effusion	Caused by inflammation or pathological changes within the pleura. Common causes include: - Pleuritis (e.g., tuberculous pleuritis). - Malignant tumours (e.g., lung, breast, or metastatic). - Autoimmune diseases (e.g., rheumatoid arthritis, systemic lupus erythematosus). - Pulmonary embolism or pancreatitis.
Transudative Effusion	It is caused by an imbalance in fluid regulation within the body, leading to fluid accumulation in the pleural cavity. Common causes include: - Heart failure (most common). - Liver cirrhosis (due to hypoalbuminemia). - Nephrotic syndrome (due to hypoalbuminemia). - Hypothyroidism.

Diagnosis

Clinical Evaluation	Medical History: Inquire about a history of tuberculosis, tumours, or chronic illnesses. Physical Examination: Chest Auscultation: Reduced or absent breath sounds. Percussion: Dullness noted over fluid-accumulated areas.
Imaging Studies	Chest X-Ray: Detects effusions >200 mL. Reveals fluid levels or signs of lung collapse. Chest Ultrasound: Highly sensitive for locating effusions and guiding thoracentesis. Chest CT Scan: Accurately shows the extent of effusion and potential underlying causes (e.g., tumours).
Thoracentesis	Under imaging guidance, pleural fluid is aspirated for analysis: Biochemical Analysis: Proteins, glucose, lactate dehydrogenase (LDH). Microbiological Testing: Bacterial cultures, tuberculosis antigens. Cytology: To rule out malignancies.
Other Diagnostic Tests	Blood Tests: Assess inflammatory markers (e.g., C-reactive protein), tumour markers, or hypoproteinaemia. Tuberculosis Testing: T-SPOT or tuberculin skin test for latent or active TB detection.

Treatment

Pleural drainage is a crucial part of managing these conditions. It involves inserting a small tube into the pleural space to drain excess fluid or air. This procedure, performed under local anesthesia and guided by imaging, helps alleviate symptoms and improve lung function. In some cases when the problem is proven to be recurrent, an indwelling pleural catheter may be inserted for long term management.