Pleural Effusion

Definition: An abnormal collection of fluid in the pleural space resulting from excess fluid production, decreased absorption, or both.

Normally, about 10 to 20 ml of fluid is present in the pleural space (similar in composition to plasma except low protein <1.5 gm/dL).

Pleural effusion

Pathophysiology

• Increase in vascular permeability: e.g., Pneumonia
• Increase in hydrostatic pressure: e.g., Cardiac failure
• Decrease in pleural pressure: e.g., Atelectasis
• Decrease in plasma osmotic pressure: e.g., Nephrotic syndrome

Causes

Clinical Features

Symptoms

• May be asymptomatic in mild effusion.
• Dyspnea: Most common symptom.
• Cough: Often mild/nonproductive. Severe cough with sputum suggests underlying pneumonia or endobronchial lesion.
• Chest Pain: Pleuritic (sharp/stabbing), exacerbated by deep inspiration. Indicates pleural irritation (infection, mesothelioma, infarction). May refer to ipsilateral shoulder/upper abdomen. Note: Pain may diminish as fluid volume increases!
• Clues for Underlying Disease:
  • CHF: Lower limb edema, orthopnea, and paroxysmal nocturnal dyspnea (PND).
  • TB: Night sweats, fever, hemoptysis, weight loss.
  • Malignancy/PE/Endobronchial pathology: Hemoptysis.
  • Synpneumonic effusion: Acute febrile episode, purulent sputum production, pleuritic chest pain.

Signs (Examination)

• Decreased chest movements on affected side.
• Stony dull percussion note.
• Absent breath sounds, decreased vocal fremitus and resonance.
• Pleural rub may sometimes be heard.
• Mediastinal shift (seen in massive pleural effusion).
• Signs of Underlying Disease:
  • Peripheral edema, distended neck veins, S3 gallop → CHF
  • Jaundice and ascites → Cirrhosis with portal HTN
  • Lymphadenopathy or palpable mass → Malignancy

Investigations

1. Imaging

• Chest X-ray: Curved shadow at base, blunting costophrenic angle ascending towards axilla. Minimum 200 ml fluid needed to produce a shadow on erect CXR.
• Ultrasound: More accurate than CXR. Guides aspiration/biopsy. Distinguishes fluid from pleural thickening.
• CT Scan: Best for showing pleural abnormalities, underlying disease, and distinguishing benign vs. malignant disease.

2. Pleural Fluid Analysis

• Aspiration Rule: Unnecessary if cause is obvious (e.g., bilateral transudate in LVF). Unilateral or unclear cause requires diagnostic tap.
• Color/Texture:
  • Straw: Transudate
  • Turbid/Purulent: Empyema
  • Hemorrhagic: Pulmonary infarction or Malignancy
  • Milky/Opalescent: Chylothorax
  • Black: Aspergillus niger, Rhizopus oryzae, malignant melanoma, charcoal-containing empyema
• Biochemical markers (Transudate vs Exudate):
  • ADA > 50 U/L or IFN-γ > 140 pg/mL supports TB.
  • Increased Amylase = Pancreatitis.
  • Increased Triglycerides/Cholesterol = Chylothorax.
  • Low pH = Infection, rheumatoid arthritis, ruptured esophagus.
• Microbiology & Cytology: Gram’s stain, culture sensitivity, AFB stain. PCR for TB should be done in most cases. Cell count, cell type, and malignant cytology should be requested.

3. Pleural Biopsy

• Combining aspiration with biopsy increases diagnostic yield.
• Typically uses an Abrams needle, better obtained under USG or CT guidance.
• Video-assisted thoracoscopy (VATS) allows operator to directly visualize pleura and obtain biopsy.

Management

• Observation: Asymptomatic transudative effusions need not be drained.
• Therapeutic Aspiration: Considered for symptomatic patients (e.g., dyspnea).
• Tube Thoracostomy (ICD): Insertion of intercostal drainage tube is required in complicated parapneumonic effusions and empyema.
• Pleurodesis: Instilling an irritant (talc, doxycycline) into pleural space to cause bridging fibrosis and obliterate the space. Used for recurrent malignant effusions.
• Treat Underlying Cause: E.g., managing heart failure, nephrotic syndrome, or pneumonia will often be followed by resolution of the effusion.