What Is It, Causes, Treatment, and More

Authors: Nikol Natalia Armata,Kelsey LaFayette, DNP, RN

Editors: Alyssa Haag,Józia McGowan, DO

Illustrator: Jessica Reynolds, MS

Copyeditor: David G. Walker

Modified: 12 Aug 2022

What is empyema?

Empyema, also known as pulmonary empyema, refers to the accumulation of infected fluid (i.e., pus) in the pleural cavity (i.e., the space between the lungs and the membrane that surrounds them). Most frequently, an empyema is associated with bacterial infections, such as bacterial pneumonia, but it may also develop after surgery or trauma to the thorax. 

Illustration of a set of lungs with a collection of pus in the right lower lobe.

What is the difference between effusion and empyema?

In general, an effusion is when fluid builds up in a body cavity. For example, a pleural effusion is a build-up of fluid, of any consistency, between the pleural space. Pleural effusions can be transudative (when fluid leaks into the pleural space as is commonly seen with heart failure) or exudative (when inflammatory conditions, like pneumonia, cause fluid to enter the pleural space). An example of an exudative effusion is a parapneumonic effusion, which occurs when fluid accumulates in the pleural space due to an adjacent pneumonia. Empyema is a subset of pleural effusion and can be considered a parapneumonic effusion if caused by an adjacent pneumonia. 

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What causes empyema?

Empyema will most commonly present as a complication of pneumonia. In fact, at least 20% of individuals with pneumonia will later develop a parapneumonic effusion that may lead to empyema. Empyemas can also occur from thoracic trauma or surgery, esophageal ruptures, or cervical infections. The microorganism causing the infection may differ depending on if the empyema is community or hospital-acquired (i.e., infection contracted outside of a healthcare setting and infection which occurs more than 48 hours after admission to the hospital, respectively). In community-acquired empyema, Gram-positive bacteria, most commonly Streptococcus, are usually identified. Gram-negative bacteria can also be the underlying cause; however, they are usually found in individuals who have other comorbidities, such as diabetes mellitus, gastroesophageal reflux disease (GERD), and alcohol use disorder. On the other hand, hospital-acquired empyema can involve more resistant bacteria, such as Methicillin-resistant S. aureus (MRSA) as well as Pseudomonas. Lastly, postoperatively or in individuals with trauma, empyemas are usually caused by S. aureus. Anaerobic organisms (e.g., Bacteroides fragilis, anaerobic cocci) are additional causes of postoperative empyemas but may be difficult to diagnose due to variations in clinical presentation and negative fluid cultures. Fungal empyemas, mainly caused from the Candida species, are rare, mostly associated with immunocompromised individuals, and tend to have a higher mortality rate.

Less frequently, empyema may occur without having previous pneumonia or interventions; this is known as idiopathic empyema.

What are the signs and symptoms of empyema?

The signs and symptoms of empyema include fever; cough; and pleuritic chest pain that worsens when the individual inhales, coughs, or sneezes. Usually, these symptoms last about 15 days and do not improve even after the administration of the appropriate antibiotic treatment. On physical examination, dullness to percussion on the affected area and abnormal sounds will be observed during auscultation, which can include decreased or absent breath sounds or fine crackles at the affected area.

How is empyema diagnosed?

Empyema is diagnosed after a thorough review of the individual’s medical history and conduction of a physical examination. The healthcare provider may auscultate the chest with a stethoscope in order to identify signs of pneumonia and fluid accumulation. Further diagnostic testing is frequently needed as many conditions may present similarly. Initially, chest X-rays are typically ordered to evaluate the presence of any pleural effusion. This characteristically appears on X-ray as blunting of the costodiaphragmatic angles, which means that the angle created by the diaphragm and rib disappears or has vague borders due to the accumulation of fluid.

If the X-ray is not indicative, an ultrasound can be performed at any time. Empyema may be suspected when the parietal and visceral pleura is thickened and separated by fluid, which appears on ultrasound as a homogenous anechoic accumulation. 

Chest CT scans are also necessary for individuals with empyema, preferably with an intravenous (IV) injection of contrast. Both ultrasound and CT scans are useful diagnostic tools with great sensitivity at revealing the empyema. Similarly, on CT, the pleura may be thickened, separated, and enhanced by the contrast. Additionally, the CT also offers better imaging of the lung parenchyma to evaluate for other pathologies. 

After all the necessary preliminary imaging, a thoracentesis (i.e., minimally invasive procedure during which a needle is inserted between the pleural space to drain the pus) is usually performed in order to drain the fluid and send it for analysis and culture. Notably, all pleural fluids should be cultivated and sent for further analysis. However, negative cultures do not exclude the diagnosis as some bacteria are more difficult to cultivate.

How is empyema treated?

Treatment of empyema usually requires both medical and surgical treatment. Most important is the rapid initiation of antibiotics to control the infection. Antibiotics are chosen empirically, depending on if the infection is community or hospital-acquired and can be altered later based on the result of the analysis and the culture. In community-acquired empyema, a third or fourth-generation cephalosporin (e.g., cefepime) is preferred. Metronidazole or ampicillin with a beta-lactamase inhibitor may be added in order to also cover the anaerobic microorganisms. Hospital-acquired, trauma-related, and surgery-related empyema may be treated with vancomycin, cefepime, and metronidazole or piperacillin-tazobactam. Antibiotics aimed at anaerobic bacteria may be added to the treatment regimen as they are very difficult to isolate. Antibiotics are usually given for two to six weeks, depending on the individual’s infection and response to treatment. There is not a proven benefit of intrapleural infusion of antibiotics.

Additionally, the collection of pus must be drained in order for the empyema to completely resolve. Tube thoracostomy refers to the insertion of a chest tube into the pleural cavity and is the most common type of drainage. The position of the tube is confirmed with an X-ray or CT scan. Blockage of the chest tube can be prevented with frequent flushing with saline. If the fluid accumulation persists, more drastic treatment options should be initiated with the insertion of larger tubes or even surgery. Chest tubes are usually removed when the daily drainage volume falls below 50 to 100 ml/day for more than two consecutive days (assuming there is no blockage in the tubes), reduction of the pleural effusion is confirmed by imaging, and the individual has resolving or no signs of infection.

Surgically, the goal of treatment is to evacuate the pus from the pleural cavity and help the lungs expand properly. In individuals requiring surgical intervention in acute empyema, video assisted laparoscopic thoracotomy (VATS) is typically the treatment of choice. It is a minimally invasive procedure that results in very little blood loss, less pain, better respiratory outcomes, decreased hospitalization, and better survival outcomes. If major complications cannot be controlled laparoscopically, the surgery may be converted to an open-thoracotomy (i.e., a major surgical procedure requiring an incision into the pleural space). 

After the acute phase of infection, some individuals may develop fibrosis at the site of the empyema and lung restriction that can cause dyspnea. Decortication, which is a surgical procedure performed to remove a fibrous tissue that has abnormally formed on the surface of the lung, chest wall, or diaphragm, may help to alleviate these symptoms. This procedure may be considered when pulmonary restriction and symptoms persist six months after the resolution of the infection and are affecting the individual’s quality of life.

What are the most important facts to know about empyema?

Empyema refers to the accumulation of infected fluid within a body’s cavity, especially the pleural space. It is commonly caused by bacterial infections and pneumonia as well as after trauma or surgery in the chest area. Signs and symptoms include fever, cough, and pleuritic chest pain. Diagnosis of an empyema usually requires a physical examination followed by imaging (e.g., chest X-rays, ultrasound, and CT scans) and minimally invasive procedures, like thoracentesis. Treatment usually consists of antibiotics and incisions into the pleural space to remove the collection of pus. 

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Related links

Anatomy clinical correlates: Pleura and lungs
Pleural effusion

Resources for research and reference

Bell, D. J. (2021, June 16). Blunting of the costophrenic angle. In Radiopaedia. Retrieved February 3, 2022, from

Garvia, V., & Paul, M. (2021). Empyema. In StatPearls. Retrieved from