Pleural Effusion: Causes, Diagnosis and Treatment

Our lungs are surrounded by a thin double layered lining called the pleura. This area normally contains minimal fluid which acts as a lubricant to allow for free movement of the lungs as they expand and collapse during breathing. In certain diseases, this space can get filled with excess fluid on either or both sides, termed as pleural effusion. The excess fluid compresses on the underlying lung tissue, thereby affecting breathing. This condition quite commonly, with a prevalence of over 400 per 100000 individuals.

Causes of Pleural Effusion

• Pneumonia
• Tuberculosis
• Lung Cancer
• Congestive Heart Failure
• Pulmonary Embolism
• Mesothelioma: This is a cancer of the pleural lining
• Empyema: this is an infected collection in the pleura
• Autoimmune conditions like Rheumatoid Arthritis, SLE or Sarcoidosis: these can be associated with inflammation of the pleura with subsequent collection of fluid
• Trauma: Injury to the chest can penetrate the pleura and lead to collection of blood within the space, called hydrothorax
• Chylothorax: This is the collection of chyle (the fluid in the lymphatics containing cholesterol and triglycerides) in the pleura, which occurs from damage to the lymphatic circulation around the lung

Symptoms of Pleural Effusion

The patient may experience symptoms depending on the underlying cause of the effusion such as cough and bloody phlegm as is seen with TB and cancers, or fevers in the case of empyema. The main symptoms include:

• Shortness of Breath
• Chest Pain which is generally of a piercing character which appears upon taking a deep breath

Diagnosis of Pleural Effusion

• Physical Examination: The physician would be able to identify a pleural effusion through a thorough examination of the patient’s chest, including listening with the stethoscope.
• Chest X ray: This confirms the presence of a pleural effusion, which can be seen on the X ray.
• Thoracentesis: This is a procedure through which some of the fluid from the pleura is collected and analysed to identify the underlying cause of the effusion. This is a simple test where a needle is inserted into the chest under guidance of an ultrasound to obtain the fluid. The tests done on the pleural fluid include Cell count including Red and white blood cells, Protein, Glucose, Lactate Dehydrogenase (LDH), Cholesterol and triglycerides, Adenosine Deaminase (this is raised in tuberculosis), Fluid Cytology (This is a test to microscopically examine the fluid to look for cells that may suggest cancer)
• Pleural Biopsy: A piece of the pleural tissue is examined microscopically to look for the likely cause.
• Computed Tomography (CT): A CT can detect even very small pleural effusions and is also useful to look at the lungs to identify any cancers or infection
• Ultrasonography: This is an easy bedside test which can help to look for an effusion and can also help in guiding the needle during thoracentesis

Treatment of Pleural Effusion

If the amount of fluid is small, the effusion usually resolves on its own as the pleural lining is able to absorb the fluid. Specific treatment including drainage of the fluid is considered if the patient is severely symptomatic or in case of accumulation of a large amount of fluid.

• Therapeutic Thoracentesis: A needle is inserted into the chest under ultrasound guidance as is done for a regular thoracentesis, but a larger amount of fluid is removed to provide symptomatic relief from breathlessness.
• Chest catheter drainage: A chest tube is left in the pleural cavity to drain out the fluid if a very large amount of fluid is present
• Sclerosing agents: These are substances that when inserted into the pleura, lead to scarring and fibrosis of the pleura eliminating the space between the two pleural layers. This is done in recurrent effusions that are seen with cancers
• Radiation and chemotherapy: These are options in the case of lung cancers to prevent recurrent effusion.
• Surgery: Occasionally a surgery may need to be done to open up the chest and remove excess fluid if they are thick and difficult to drain which is seen with infections
• Antibiotics: These are required for treatment of empyema and for TB, where antibiotics are needed for a longer duration.

Prognosis of Pleural Effusion

The long term course is determined by the underlying disease. In malignant pleural effusion that arises from cancers the effusion is recurrent and difficult to manage. Frequent drainage may help with symptoms, but does not stop progression of the disease. Effusions that occur from underlying infection and inflammation usually resolve completely with treatment of the disease.

References:

• Karkhanis VS, Joshi JM. Pleural effusion: diagnosis, treatment, and management. Open Access Emerg Med. 2012 Jun 22;4:31–52.
• Sahn SA, Huggins JT, San Jose E, Alvarez-Dobano JM, Valdes L. The Art of Pleural Fluid Analysis. Clinical Pulmonary Medicine. 2013 Mar;20(2):77.