PLEURAL EFFUSION


GENERAL FEATURES


• A pleural effusion is defined as an abnormal accumulation of fluid within the pleural space.


• There are two major types of pleural effusions: transudates (watery fluid) and exudates (protein-rich fluid).


– Transudative effusions are typically caused by systemic factors that affect pressures and fluid balance, such as heart failure, cirrhosis, or nephrotic syndrome. 


– Exudative effusions are most commonly caused by an increased capillary permeability or decreased lymphatic clearance, typically from inflammation, infection, or cancer.


• Other potential types include empyema, hemothorax, and chylous.


• Heart failure is widely accepted as the most common cause of pleural effusions.


CLINICAL ASSESSMENT


• History


– Frequently reported symptoms include dyspnea, cough, and respirophasic chest discomfort. 


– Patients with smaller effusions are likely to be asymptomatic. 


– Weight loss and weakness may suggest a malignant cause.


• Physical examination


– Diminished breath sounds over fluid collection


– Dullness to percussion


– Decreased tactile fremitus


DIAGNOSIS

• Chest radiography should be 
ordered in frontal and lateral views.


• Chest CT should be considered to rule out malignancy or tuber­culosis (TB) and to further eval­uate the location and degree of effusion.


• Chest ultrasound is becoming increasingly valuable in the evaluation of effusions and is typically 
obtained in conjunction with potential thoracentesis.


• Thoracentesis can be both diagnostic and therapeutic. Aspirated fluid can be sent for analysis of protein, glucose, lactate dehydrogenase, WBCs, cytology, and culture.


– Exudates should meet at least one of the following criteria (Light's criteria): 


· pleural fluid protein to serum protein ratio >.05


· pleural fluid LDH to serum LDH ratio >0.6


· pleural fluid LDH greater than two-thirds the upper limit of normal serum LDH 


– Transudates typically do not meet any of the above criteria.


– If evaluation supports an exudative effusion, fluid should also be sent for Gram's stain, culture, and cytology.


– Frankly purulent fluid supports the diagnosis of an empyema; sputum and blood cultures should be ordered. A pleural fluid LDH level >1,000 IU/L is also suggestive.


– Elevated WBC count suggests infection or parapneumonic 
effusion.


– Elevated protein suggests 
TB-related effusion or, if very elevated, Waldenstrom's 
macroglobulinemia.


– Low glucose suggests effusion from autoimmune disease (rheumatoid arthritis, lupus), para­pneumonic effusion, TB, malignancy, or esophageal rupture.


– Gross blood suggests a hemothorax.


– Milky translucent fluid suggests a chylothorax.


TREATMENT

• Treatment should be directed at the suspected underlying cause. 


– Diuretics for heart failure, antibiotics for pneumonia, and chemotherapy or radiation for malignancy


• Thoracentesis is a viable option for symptomatic relief of all types of pleural effusions.


• A tube thoracostomy (chest tube) should be placed for continued drainage.


• Pleurodesis and thoracostomy are indicated mainly for palliation when treating effusions related to malignancy.


• Fibrinolytic agents injected through chest tubes have been reported to improve drainage in patients with loculated effusions. 


• Tunneled catheter placement is considered for patients who require long-term drainage in special circumstances.


• Surgical management, in the form of decortication, may be necessary in treating empyema.