Pleural effusion is the abnormal accumulation of fluid in the pleural space, occurring due to various conditions affecting fluid production or drainage. It can be classified as transudative or exudative based on the fluid characteristics and is commonly associated with diseases like pneumonia and heart failure. Diagnosis involves imaging, fluid analysis, and management is focused on treating the underlying cause.

1. P H Y S I O L O G Y
P A T H O L O G Y
M A N A G E M E N T
Pleural Effusion

2. Pleural Fluid:
 Pleural space normally contains 5-10 ml of pleural fluid.
 This lubricates the apposing surfaces of the visceral & parietal pleurae during
respiratory movements.
 It is formed by presence of hydrostatic & osmotic pressures.
 Excreted via parietal pleura capillaries (higher hydrostatic pressure) and
absorbed into the capillaries of visceral pleura (lower hydrostatic pressure).
 Any condition that increases production or impairs drainage of fluid results in
abnormal accumulation in pleural space between lining of the lungs & thoracic
cavity, known as pleural – effusion.

3. Pleural Effusion:
 Pleural effusion is a common manifestation of both primary & secondary
pleural diseases, which may be inflammatory or non-inflammatory.
 Accumulation of pleural fluid is not a specific disease, but rather a reflection of
underlying pathology.
 Source of the fluid is usually blood vessels or lymphatic vessels lying beneath
either pleura, but occasionally an abscess or other lesion may drain into pleural
space.
 Can occur in the following setting:
i. Increased hydrostatic pressure: as in congestive heart failure.
ii. Increased vascular permeability: as in pneumonia.
iii. Decreased osmotic pressure: as in nephrotic syndrome.
iv. Increased intrapleural negative pressure: as in atelectasis.
v. Decreased lymphatic drainage: as in mediastinal carcinomatosis.

4. Pleural Effusion:
 Transudate is a filtrate, hence, it is a clear fluid with a low protein & cell
count.
 Exudate, on the other hand, is a cloudy fluid with a high protein & cell
count;
 as lesions responsible for the outflow of exudate allow larger molecules &
even solid matter to pass into the pleural space.
 The effusion follows gravity & usually collects in the lower margins of
the pleural space.

5. Pleural Fluid:
 Generally, fluid accumulates as a result of:
A. Increased hydrostatic pressure or decreased osmotic pressure
(“transudative” effusion).
B. Increased microvascular pressure due to disease of the pleural surface
itself or injury in the adjacent lung (“exudative” effusion).

6. Etiology:
 Common causes:
 Pneumonia
 Cardiac failure
 Subdiaphragmatic disorders
(subphrenic abscess, pancreatitis,
etc.)
 Tuberculosis
 Pulmonary infarction
 Malignant disease
 Uncommon causes:
 Hypoproteinaemia (nephrotic
syndrome, liver failure,
malnutrition).
 Connective tissue disorder (SLE,
rheumatoid arthritis)
 Acute rheumatic fever
 Post-myocardial infarction
syndrome.
 Myxoedema
 Uraemia
 Meigs’ syndrome (ovarian tumor +
plural effusion)
 Asbestos-related.

7. Clinical Features:
 Pain on inspiration + coughing/sneezing.
 Pleuritic chest pain.
 May be localized or referred.
 Non-productive cough.
 Breathlessness (dyspnea) is the only
symptom related to the effusion itself, & its
severity depends on the size & rate of
accumulation.
 Inspection:
 Tachypnoea
 Palpation:
 Decreased chest expansion on affected side.
 Trachea & apex may be shifted towards
unaffected side.
 Reduced tactile vocal fremitus.
 Percussion:
 Stony dull tone.
 Usually the R mid- and lower- zones.
 Auscultation:
 Absent breath sounds
 Diminished or absent vocal resonance at
affected side.
 Crackles above effusion.

8. Diagnosis:
 The diagnostic evaluation of pleural effusion includes:
 chemical
 microbiological studies
 as well as cytological analysis, which can provide further information about the
etiology of the disease process.
 Immunohistochemistry provides increased diagnostic accuracy.

9. Imaging:
 Chest x-ray & ultrasound are usually performed as first-line tests to
diagnose pleural effusion.
 Standard PA & lateral views remain the most important technique for
initial diagnosis of pleural effusion.
 But thorax CT is sometimes required (e.g. for very small effusions).

10. Imaging:
 CXR:
 Around 200 mL of fluid is required to be detectable on a PA chest x-ray.
 Smaller effusions can be identified by ultrasound or CT.
 Classical appearance of pleural fluid on the erect PA chest film is of a curved
shadow at the lung base, blunting the costophrenic angle & ascending
towards the axilla.
 Previous scarring or adhesions in the pleural space can cause localized
effusions.
 Fluid localized within an oblique fissure may produce a rounded opacity,
simulating a tumour.

11. Imaging - CXR:
A. X-ray chest, PA view, with
fissural effusion.
B. X-ray chest, lateral view, with
fissural effusion.

12. Imaging:
 Ultrasonography:
 Is more accurate than plain CXR for determining the volume of
pleural fluid & frequently provides additional helpful information.
 Visualisation of fluid facilitates skin marking to indicate a site for
safe needle aspiration & guides pleural biopsy, increasing diagnostic
yield.
 Technique may also distinguish pleural fluid from pleural thickening.
 CT:
 Displays pleural abnormalities more readily than either plain
radiography or ultrasound, & may distinguish benign from
malignant pleural disease.

13. Imaging – CT thorax:
• Contrast-enhanced computed
tomography: split pleural
sign
• Split pleural sign refers
to thickening &
increased contrast
enhancement of the
visceral & parietal pleura
separated by empyema
or an exudative effusion.

14. Pleural aspiration & biopsy:
 In most cases, sampling is necessary to establish a diagnosis.
 Is the PREFERRED investigation (pleural tap).
 Simple aspiration provides information on the color & texture of fluid & on
appearance alone may immediately suggest an empyema or chylothorax.
 Presence of blood consistent with pulmonary infarction or malignancy, but may
also represent a traumatic tap.
 Gram stain of pleural fluid may indicate para-pneumonic effusion.
 Cytological examination is essential.
 A low pH suggests infection, but also seen in rheumatoid arthritis, ruptured
oesophagus or advanced malignancy.

15. Pleural aspiration & biopsy:
 Aspiration should not be performed for bilateral effusions in a clinical setting
strongly suggestive of a pleural transudate.
 Differentiation between transudate & exudate is crucial before further tests are
undertaken.
 Hemorrhagic effusions can be differentiated from traumatic pleural taps by
observing serial samples of pleural tap which clear up in the case of a traumatic
pleural tap.
 The routine pleural fluid evaluation usually includes determination of:
 Protein
 pH
 Lactate dehydrogenase (LDH).
 Glucose & albumin levels, with adenosine deaminase levels
 Cell count for differential & cytological examination.

16. Pleural Fluid Analysis:
 Light’s criteria (transudate vs. exudate):
 Pleural fluid is an exudate if ONE or MORE of the following criteria are
met:
 Pleural fluid protein : serum protein ratio > 0.5
 Pleural fluid LDH : serum LDH ratio > 0.6
 Pleural fluid LDH > two-thirds of the upper limit of normal serum LDH.
 NB: *LDH – lactate dehydrogenase.

17. Malignant Pleural Effusion:
 Is a common complication of cancer.
 40% of all pleural effusions are due to malignancy.
 Most common causes are lung & breast cancers, & presence of effusion
indicates advanced & incurable disease.
 Pleural aspirate is the key investigation & may show malignant cells.
 In fact, the most common diagnosis with a massive effusion is malignancy,
other causes being complicated parapneumonic effusions & tuberculosis.

18. Differential Diagnoses:
 Bacterial pneumonia.
 Pulmonary thromboembolism (pulmonary infarct).
 Carcinoma.
 Connective tissue disorder.
 TB.

19. Management:
 To treat pleural effusion appropriately, it is important to determine its etiology.
 However, the etiology of pleural effusion remains unclear in nearly 20% of cases.
 First of; stabilize patients with respiratory distress.
 Therapeutic aspiration may be required to palliate breathlessness.
 An effusion should never be drained to dryness before establishing a diagnosis.
 Treatment of underlying cause – for example, heart failure, pneumonia,
pulmonary embolism or subphrenic abscess – will often be followed by
resolution of the effusion.

20. Treat Underlying Cause:
 Acute congestive heart failure – loop diuretics.
 Collagen vascular diseases – steroids.
 Pancreatitis.
 Pancreaticopleural fistula – endoscopic or surgical intervention is
recommended.
 Meigs syndrome – removal of ovarian tumor is recommended.
 Other malignancy: targeted cancer immunotherapy, chemotherapy,
radiotherapy, or surgical resection.