A pleural effusion is the excessive accumulation of fluid between the two layers of pleura that surrounds the lungs (pleural space). There is continuous formation of fluid in the pleural cavity which is continuously reabsorbed. This is normal. The balance between secretion and reabsorption is such that only a small amount of pleural fluid exists in the cavity – about 15mL. Small pleural effusions may cause mild or no symptoms. Large pleural effusions can limit the normal expansion of the lungs during breathing.
Diagnosis of a Pleural Effusion
Signs of a Pleural Effusion
A pleural effusion is detectable clinically only when the quantity of accumulated fluid exceeds 500 ml. The following signs may be evident :
- Chest movement in relation to breathing is reduced on the affected side.
- Breath sounds are reduced on the affected side.
- Percussion over the fluid-filled area gives a dull note (stony dullness).
- Tracheal deviation may be a result of the lungs being pushed opposite to the affected side as a result of a massive effusion.
X-ray, Ultrasound and CT Scan
Radiological investigation is the most useful test for detecting the presence of pleural effusion. A minimum of 300 ml of fluid accumulation is required for producing a significant radiological finding (blunting of costophrenic angle) on a regular chest x-ray (posterioanterior view). Effusions as small as 150 ml can be seen on a chest x-ray taken in special views (lateral decubitus view).
Picture of Normal Chest X-Ray (Posterioanterior View)
Picture of Chest X-Ray with a Pleural Effusion (Source : Wikimedia Commons)
An ultrasound and CT scan may provide more detailed and accurate information about the pleural effusion. These investigations can also highlight other abnormalities that may be present in the lungs and pleura. Radiological investigations can also differentiate pneumothorax (accumulation of air in pleural cavity) and hydropneumothorax (accumulation of air and fluid in pleural cavity) from a pleural effusion.
Pleural Tap, Biopsy and Exploration
Certain invasive diagnostic procedures are usually performed to determine the cause of the pleural effusion. Pleural tap (thoracentesis) is most important invasive diagnostic procedure performed in individuals with pleural effusion. Other invasive procedures include pleural biopsy and pleural exploration.
Treatment of a Pleural Effusion
The management of a pleural effusion depends on the cause. It is possible for a pleural effusion to resolve spontaneously in some patients. Excessive fluid may be drained for symptomatic improvement along with the measures adopted for the treatment of the cause. In patients with milder effusions, an extended pleural fluid aspiration (therapeutic thoracocentesis) following the diagnostic pleural tap is usually sufficient. Therapeutic thoracentesis involving removal of larger amounts of fluid may require insertion of a tube drain. More than 1 to 1.5 liter pleural fluid should not be removed at a time as it can lead to pulmonary edema (fluid in the lungs). Read more on drainage of pleural fluid.
Recurrent Pleural Effusions
Recurrent pleural effusions causing significant respiratory difficulty are treated more aggressively. Repeated pleural tap may be carried out in such cases. If the effusion is not satisfactorily controlled with pleural taps, tube drainage or thoracoscopic drainage is done. It may be combined with chemical pleurodesis. The effusion is drained as complete as possible. The chemical pleurodesis may be done if the effusion drained per day falls to 150 ml.
Chemical pleurodesis involves scarring the two opposing layers of pleura with chemicals like talc, doxycycline or bleomycin. The chemicals are instilled through the chest tube or following the thoracoscopic drainage. The procedure results in formation of adhesions which prevents accumulation of fluid between the two layers.
Failure of pleurodesis to yield the desired resulst can be managed with placement of chest tube with one-way valve. Drainage with this can be done daily and can be managed from home. Highly refractory pleural effusions may require mechanical pleurodesis (scarring the pleura mechanically during surgery) or pleurectomy.
Treating an effusion in different diseases
Majority of the transudative effusions improve with the correction of the underlying disease like heart failure, nephritic syndrome and so on.
Effusions resulting from lung infections, like pneumonia or a lung abscess, can resolve spontaneously with antibiotic therapy or sometimes may require drainage. Complicated effusions with pus in the pleural cavity (empyema) require immediate drainage and aggressive empirical antibiotic therapy. It is usually drained with a chest tube.
Tuberculous pleural effusions are usually mild and resolve within few weeks of initiation of anti-tubercular treatment. A short course of corticosteroids may be needed in seriously ill patients. Surgical drainage is rarely required in tuberculous effusions.
Effusion resulting from rupture of esophagus is treated with immediate surgical closure of the esophagus. A delayed surgical closure should be supported with antibiotic coverage against anaerobic bacteria, and pleural drainage.
Pleural effusion associated with immunological disorders like rheumatoid arthritis or lupus may resolve spontaneously in some patients. Some patients require short course of steroid therapy for resolution of effusion.
A pleural effusion resulting from malignancy is best managed with a combined approach. The approach involves the treatment of malignancy and treatment of the effusion. The effusion is managed with thoracocentesis, chest tube insertion, or VATS drainage. Recurrent effusions resulting from malignancy may be treated with permanent pleural drainage catheter, pleurodesis (chemical or mechanical) or open surgical pleurectomy.