Pleural Effusion (Etiology and Different Varieties)

Pleural effusion is a common clinical finding with many potential underlying causes. It refers to fluid accumulation in the pleural space between the lung and the chest wall. This condition can result from various underlying conditions, such as heart failure, pneumonia, cancer, tuberculosis, and kidney disease.

Knowledge of pleural effusion is essential for medical professionals as it can be a significant diagnostic and therapeutic challenge.

In this blog we’ll discuss the etiology and different varieties of pleural effusion is important medicine topic for NEET PG exam preparation.

Introduction

• Normal amount of fluid in Pleural space: 5-15 ml
• Pleural fluid secreted by: Parietal Pleura
• Rate of synthesis of pleural fluid : 0.01 ml/kg/hr (Some of this secreted fluid is reabsorbed by lymphatics)
• Minimal Amount of fluid present in pleural cavity for Clinical Detection → 300ml.
• IOC for Minimal Pleural Effusion: CT chest > USG chest
• Minimal Amount of fluid that should be present to confirm pleural effusion on CXR in Upright position
• CXR Upright : Lateral view > 100ml
• CXR Upright : Frontal view > 200ml
• CXR Upright : Frontal view (Amount of fluid needed for obliteration of Hemi-diaphragm: > 500 ml
• Characteristic of Pleural effusion on CXR
  • Obliteration /Blunting of CP angle (CP Angle → Costophrenic Angle)
  • Meniscus sign

Etiology

• 2 types of PE
  • Transudative
  • Exudative

TRANSUDATIVE VARIETY

Hydrostatic Pressure will drive the fluid out of vascular space/capillaries while Oncotic pressure will drive the fluid back into Intravascular compartment

• Any condition causing
• Conditions causing ↑ in Hydrostatic Pressure
  • CHF (MC)
  • Constrictive Pericarditis
  • Valvular lesions
• Conditions causing ↓ in Oncotic pressure
  • Oncotic Pressure α Blood Albumin
  • ↓ Blood Albumin (HypoAlbuminemia) → ↓ Oncotic Pressure

Exudative Variety

• Causes of Exudative Pleural Effusion
  • Parapneumonic Effusion (Pleural Effusion + Pneumonia)
  • Malignancy
  • TB
  • Rheumatoid Effusion
  • Meigs Syndrome

Different Varieties Of Pleural Effusion

1. Pleural Effusion related to Malignancy

• Usually there is occurs Massive Pleural Effusion in Malignancy (peripherally located cancer)

• Symptoms → Pt. C/O TREPEPNEA → Dyspnea of Patient is Increasing on lateral Decubitus position.
• Management
  • Diagnostic Thoracocentesis
    • Send the fluid to laboratory to confirm the Exudative variety based on LIGHT’s Criteria
  • Check for
    • Pleural Fluid Protein
    • Pleural Fluid LDH
  • Ideally any 1 of 3 present is sufficient for Diagnosis of Exudative Pleural Effusion.
    • However, in about 25% of cases light’s criteria may misdiagnose Transudate as Exudate.
  • Therefore we also check
    • Pleural fluid Sugar < 60 mg%
    • Cytology: Microscopic examination : Cancer Cells + nt
    • Pleural effusion in these cases of Malignancies recurs a lot after Thoracocentesis. To prevent this, we inject a sclerosing agent in pleural space which causes obliteration of pleural cavity and the fluid doesn’t reaccumulate. This procedure is k/as Pleurodesis

• Rx: After Removing the fluid from pleural space, give the following drugs:
  • Injection Doxycycline Into pleural space via chest tube: Leads to formation of Adhesions in various layers of pleura ultimately causing Pleurodesis
  • Procedure of choice for Mx of patients with Malignant pleural effusion → Pleurodesis

2. Parapneumonic Effusion

• If Diagnosed later or failed to Diagnose: Can lead to Empyema which then is managed by Chest tube insertion in 5th ICS in Mid Axillary line.

3. Tubercular Pleural Effusion

• Classified as Extra-pulmonary TB
• Adenosine Deaminase Levels ↑ in Pleural fluid
• IOC - Pleural Biopsy gene Xpert / CBNAAT (Not Pleural Fluid gene Xpert)

4. Rheumatoid Pleural Effusion

• Inflammatory nodules in Lungs, Heart

• On Skin present in Extensor Distribution
• Inflammatory nodules undergo Breakdown that results in development of Exudates
• On Microscopic Examination
• Cholesterol crystals +nt in Pleural Fluid

5. Meigs syndrome

• Associated with
  • Ovarian Tumors
  • Fibroma / Thecoma
• Ascites
• Rt. sided Pleural effusion

Normal Pleural Fluid has the following characteristics              

• Clear Ultrafiltrate of plasma that originates from the Parietal pleura
• A pH of 7.60-7.64
• Protein content of less than 2% (1-2 g/dL)
• Fewer than 1000 white blood cells (WBCs) per mm3.
• Glucose content similar to that of plasma
• Lactate dehydrogenase (LDH) less than 50% of plasma

INDICATIONS OF ICD TUBE INSERTION

1. Loculated Pleural Fluid / Empyema 
2. Pleural fluid PH < 7.20
3. Pleural Fluid glucose < 3.3 mmol/L (< 60 mg / dl)
4. + ve Gram stain or culture of pleural fluid
5. Presence of Gross pus in the pleural Space

Characteristics Of Important Exudative Pleural Effusion

GROSS APPEARANCE OF PLEURAL FLUID

A. Haemorrhagic pleural effusion 

B. Chylous pleural effusion

c. Transudative Pleural effusion

• Chylous Thoracic duct obstruction leads to Chylothorax: This Pleural Fluid is Milky White Colored and has ↑ Triglycerides
  • Cause of Chylothorax → Damage to lymphatics by Conditions such as Filariasis

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