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

Etiology or Type ofEffusion	Gross appearance	White Blood Cell Count(cells/mcL)	Red Blood Cell Count(cells/mcL)	Glucose	Comments
Malignancy	Turbid  to bloody: occasionally serous	1000 to<  100,000 M	100 to several hundred thousand	equal to serum levels: < 60 mg/dl. In 15 % of cases	Eosinophilia uncommon; positive result on cytologicexamination
Uncomplicated parapneumonic	Clear to turbid	5000-25,000 P	< 5000	equal to serum levels	Tube  thoracostomyunnecessary
Empyema	turbid to purulent	25,000- 100,000 P	< 5000	Less than Serum levels: often very low	drainage necessary; putrid odor suggests anaerobicinfection
Tuberculosis	Serous to serosanguineous	5000- 10,000M	< 10,000	Equal  to serum levels: occasionally< 60 mg/dL.	protein > 4.0 g/dL (may exceed 5 g/dL); eosinophils cells (> 10%) or mesothelial cells (>5%) make diagnosis unlikely: see text for additionaldiagnostic tests
Rheumatoid	Turbid; greenish yellow	1000-20,000 M or P	< 1000	< 40 mg/dl	Secondary empyema common; high LD, low complement, high rheumatoid factor, cholesterolcrystal areCharacteristic
Pulmonary infarction	serous to grossly bloody	1000-50,000 M or P	100 to100,000	equal to serum levels	variable findings: no pathognomonicfeatures
Esophageal rupture	turbid to purulent red- brown	< 5000 to50,000 P	1000-10,000	usually, low	high amylase level (salivary origin); pneumothorax in 25% cases; effusion usually on left side: pH< 6.0 strongly suggestsDiagnosis
Pancreatitis	Turbid to serosanguineous	1000-50,000 P	1000-10,000	equal to serum levels	Usually  left- sided; highamylase level

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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