Pleural Effusion

What is a Pleural Effusion?

Pleural effusion refers to an abnormal accumulation of fluid in the pleural space — the thin gap between the lung and the chest wall. Normally, this space contains only a small amount of lubricating fluid (＜ 15 mL).

Imaging Appearance

On CT scan, pleural effusion typically appears as:

• Crescent-shaped fluid collection along the lung base
• Dependent layering — fluid settles in the lowest part of chest when upright
• Meniscus sign on chest X-ray
• Loss of costophrenic angle sharpness

CT is superior to X-ray for detecting small effusions and distinguishing fluid from other abnormalities.

Types of Pleural Effusion

Transudative Effusion

Caused by fluid leakage due to increased pressure or low protein:

• Heart failure (most common)
• Cirrhosis
• Kidney disease
• Pulmonary embolism

Lab characteristics:

• Low protein (＜ 3 g/dL)
• Low LDH
• Clear appearance

Exudative Effusion

Caused by inflammation or infection:

• Pneumonia (parapneumonic effusion)
• Cancer (lung, breast, lymphoma)
• Pulmonary embolism
• Tuberculosis
• Autoimmune disease (lupus, RA)

Lab characteristics:

• High protein (＞ 3 g/dL)
• High LDH
• May be cloudy or bloody

Symptoms

Depending on the amount of fluid:

• Shortness of breath (dyspnea)
• Sharp chest pain (pleuritic pain)
• Dry cough
• Difficulty breathing when lying flat

Small effusions may cause no symptoms.

Diagnosis

Your doctor may order:

1. Thoracentesis (Fluid Sampling):

• Needle inserted to remove and analyze fluid
• Determines if transudative vs. exudative

2. Pleural Fluid Analysis:

• Cell count (WBC, RBC)
• Protein, LDH, glucose
• Cytology (cancer cells)
• Culture (infection)

3. Imaging:

• Chest X-ray
• CT scan (best for small effusions)
• Ultrasound (guides procedures)

Treatment

Depends on the underlying cause:

Transudative:

• Treat heart failure (diuretics)
• Manage cirrhosis or kidney disease

Exudative:

• Antibiotics for infection
• Drainage for large effusions
• Chemotherapy for malignant effusion

Large or symptomatic effusions:

• Therapeutic thoracentesis (drain fluid)
• Chest tube placement
• Pleurodesis (prevent recurrence)

Prognosis

Outcomes depend on the cause:

• Heart failure effusions often improve with diuretics
• Infectious effusions usually resolve with antibiotics
• Malignant effusions indicate advanced cancer and may require palliative drainage

What Should You Do?

1. Identify the cause - Work with your doctor to find the underlying condition
2. Monitor symptoms - Track breathing difficulty, fever, chest pain
3. Follow treatment plans - Take medications as prescribed
4. Repeat imaging if recommended to ensure resolution

Related Imaging Terms

• Empyema - Infected pleural fluid (pus)
• Hemothorax - Blood in pleural space
• Atelectasis - Lung collapse often seen with effusion

Medical Disclaimer: This information is educational only. Pleural effusion requires professional medical evaluation and management.