Accumulation of serous fluid between parietal pleura and visceral pleura is called pleural effusion. Accumulation of purulent fluid is called empyema.
The term hydrothorax denotes passive transudation of fluid into the pleural cavity. This occurs in congestive heart failure, nephrotic syndrome, cirrhosis of liver, severe malnutrition, etc.
A minimum of 500 mL of fluid is necessary for clinical detection of pleural effusion.
Transudate is an ultrafiltrate of plasma, resulting from increased hydrostatic pressure or decreased serum oncotic pressure. This is essentially an effusion with normal pleura.
Exudate resembles plasma, and is rich in proteins. This results from increased capillary permeability. This is essentially an effusion with diseased pleura.
Congestive heart failure, cirrhosis of liver, nephrotic syndrome, severe malnutrition
Tuberculosis, malignancy, pneumonia, pulmonary infarction, rheumatoid arthritis, pancreatitis, systemic lupus erythematosus, drug-induced effusion, benign asbestos-related effusion, Dressler's syndrome, intra-abdominal abscess, Meigs' syndrome, chylous pleural effusion
Symptoms and signs of pleurisy may precede the development of pleural effusion.
Breathlessness may occur, the severity of which is related to the size and rate of accumulation of fluid.
Physical findings in the chest
Inspection and palpation will disclose shift of trachea and mediastinum (shift of apex beat) to the opposite side, reduction in the chest movements on the affected side, bulging of the intercostal spaces, fullness of the affected chest, and markedly reduced vocal fremitus. Measurements reveal diminished chest expansion, increase in the size of the affected hemithorax and an increase in spino-scapular distance.
Percussion reveals a stony dull note over the fluid. Upper level of the dullness is highest laterally in the axilla, and is lower anteriorly and posteriorly (Ellis-S-shaped curve). A small pleural effusion on the left side may be detectable only by the obliteration of Traube's space on percussion. Likewise, a small effusion on the right side may be detectable only by tidal percussion.
On auscultation, intensity of the breath sounds is markedly diminished-to-absent over the fluid. Adventitious sounds are not audible. Vocal resonance is markedly diminished over the fluid. Rarely, aegophony, whispering pectoriloquy and a tubular bronchial breathing may be audible just above the level of a pleural effusion.
Grocco's sign (Grocco's triangle; paravertebral triangle of dullness)
In moderate to large sized pleural effusions, a triangular area of dullness or impaired note can be percussed over the back of chest on the contralateral side or opposite side of the effusion. This is probably due to shift of the posterior mediastinum to the opposite side by effusion.
The Grocco's triangle is bounded medially by the midspinal line from the upper level of effusion down to the level of the tenth thoracic vertebra. It is bounded below by a horizontal line of about 3-7 cm extending laterally from the tenth thoracic vertebra, along the lower limit of lung resonance. It is bounded laterally by a curved line connecting the above two lines.
Chest radiograph (postero-anterior view) in the erect posture can detect pleural effusion. A minimum of 300 mL of fluid is required for detection in this view.
Chest radiograph (anteroposterior view) in the supine posture needs even larger amounts for detection. Here, the fluid layers out posteriorly and gives a generally hazy shadow (ground glass appearance). This is the usual radiological appearance in bedridden patients.
Chest radiograph (lateral decubitus view) with the affected side down, can detect an effusion as small as 100-150 mL.
Radiological features of pleural effusion in an erect chest film
Mediastinal shift to the opposite side
Obliteration of costophrenic angle
A dense uniform opacity in the lower and lateral part of hemithorax
Upper border of the opacity is concave upwards and is highest laterally
Wider than normal interlobar fissure in interlobar effusion'
Encysted interlobar effusion may be seen as a rounded opacity resembling solitary pulmonary nodule (phantom tumour) o Shift of mediastinum toward the side of effusion in a patient with massive effusion indicates either an endobronchial obstruction or a mediastinum encasement by tumour (e.g. mesothelioma)
It is useful in differentiating loculated pleural effusion from pleural tumour. o Useful in localisation of an effusion prior to aspiration and biopsy.
Pleural aspiration and fluid analysis
At diagnostic aspiration, at least 50 mL of pleural fluid should be withdrawn. The fluid is collected in separate
containers for microbiological examination including culture for tuberculosis, cytological examination including malignant cells and biochemical examination.
Exudative fluid can be differentiated from transudative fluid as per the table given on the next page.
A low pleural fluid glucose concentration (<60 mg/dL) suggests empyema, malignancy or tuberculosis. Very low levels (<15 mg/dL) are characteristic of rheumatoid effusions.
Pleural fluid eo§inophilia (>10% of all cells) may be seen in resolving infections, hydropneumothorax and asbestos-related pleural effusion.
Pleural fluid erythrocyte counts exceeding 100,000/mm3 are most often seen in malignancy and pulmonary embolism.
Pleural fluid pH is a very unreliable guide to differentiate between transudates and exudates. However, a pleural fluid pH below 7.2 in a patient with a parapneumonic effusion indicates the need for drainage of the fluid.
Pleural fluid amylase is elevated in patients with pancreatic diseases and oesophageal rupture. However, routine amylase estimation is not recommended unless the clinical features suggest either of the two diseases.
Pleural fluid determination of antinuclear antibody titres or rheumatoid factor levels adds little diagnostic information and is not indicated in most cases.
Other special characteristics of pleural fluid in relation to various diseases are discussed along with individual diseases (ADA estimation discussed under "tuberculous pleural effusion")
Usually indicated in some exudates which are undiagnosed.
Closed pleural biopsy can be performed with Abrams or Cope or True-cut needle. It should be done under ultrasound guidance when the effusion is small or loculated.
The needle should be inserted through an intercostal space at the area of maximum dullness on percussion and at the site of maximum radiological opacity or at a site determined by ultrasonography.
Other investigations in pleural effusion
Blood examination for total and differential leucocyte counts, ESR, proteins, sugar, LDH, amylase, rheumatoid factor and antinuclear factor.
Sputum examination for tubercle bacilli and malignant cells.
In a massive effusion, a repeat radiograph after removal of a large volume of fluid may reveal an underlying parenchymal lesion.
Biopsy or fine-needle aspiration of scalene lymph nodes. Bronchoscopy and biopsy.
Thoracoscopy and biopsy.
Management of pleural effusion
Treatment of the underlying cause.
Therapeutic aspiration may be necessary to relieve dyspnoea. Not more than 1 L should be removed at a sitting because pulmonary oedema may follow removal of large volumes.
Insertion of chest tube if rapid re-accumulation of fluid occurs.
Pleurodesis for malignant effusion.