Empyema is a severe infection within the chest cavity. It is defined as a collection of pus in the pleural space, which is the thin area between the lung and the inner surface of the chest wall. This pus is a thick fluid composed of white blood cells, dead tissue, and bacteria, reflecting a significant localized infection. Because of its location, this infected material cannot be expelled through coughing and requires medical intervention for drainage.
What Empyema Is and How It Develops
The pleural space is normally a narrow, fluid-filled gap bordered by two membranes: the visceral pleura covering the lung and the parietal pleura lining the chest wall. This small amount of fluid acts like a lubricant, allowing the lungs to slide smoothly against the chest wall during breathing. Empyema begins as a complication of another infection, which causes fluid to accumulate in this space, a condition known as a parapneumonic effusion.
The progression of empyema occurs in a continuous three-stage process. The first is the exudative stage, which involves the rapid accumulation of thin, sterile or near-sterile fluid in the pleural space as a result of increased capillary permeability. This stage typically lasts for a few days before bacteria begin to invade the fluid.
The second stage is the fibrinopurulent phase, where the infection becomes established, and the fluid thickens into pus due to the high concentration of bacteria, white blood cells, and cellular debris. Fibrin, a protein involved in clotting, is deposited on the pleural surfaces, creating fibrous strands that divide the fluid collection into pockets, a process called loculation. The organizing stage, which can take weeks to develop, is characterized by the growth of fibroblasts into the fibrin deposits, forming a thick, inelastic layer known as a pleural peel. This dense peel encases the lung, preventing it from fully expanding and leading to restricted breathing.
Primary Causes and Who Is At Risk
Empyema is almost always a secondary condition, arising as a complication of another infection or medical event. The most frequent cause is bacterial pneumonia, where the infection spreads directly from the lung tissue into the adjacent pleural space. Empyema is a direct result of complicated bacterial pneumonia in up to 70% of cases.
Other initiating factors include recent thoracic surgery, chest trauma or injury, and lung abscesses, which can directly introduce bacteria into the pleural cavity. In rare instances, an infection may spread to the chest from a distant site in the body via the bloodstream.
Individuals with underlying chronic lung diseases, such as Chronic Obstructive Pulmonary Disease (COPD) or bronchiectasis, are more susceptible. Conditions that compromise the immune system also increase vulnerability, including diabetes, alcoholism, and immunocompromised states. Advanced age is also a risk factor, as patients over 70 may have a less robust immune response and a higher likelihood of recent hospital stays.
Identifying the Symptoms
The symptoms of empyema often overlap with those of the initial infection, like pneumonia, but they tend to be more persistent and severe. A high fever and shaking chills are common signs of a significant bacterial infection. Patients frequently experience pleuritic chest pain, which is a sharp, stabbing discomfort that worsens noticeably with deep breaths or coughing.
Shortness of breath, or dyspnea, is a prominent symptom, occurring because the accumulating pus puts pressure on the lung, restricting its ability to fully inflate. Other symptoms of severe infection include excessive sweating, particularly night sweats, and a pervasive feeling of fatigue (malaise). If a patient is already being treated with antibiotics for pneumonia, the developing empyema may be difficult to recognize, as the medication can partially mask or alter the typical progression of symptoms.
Diagnostic Procedures and Staging
Confirming a diagnosis of empyema and determining its stage requires a combination of imaging and fluid analysis. The initial step typically involves a Chest X-ray, which can confirm the presence of an abnormal fluid accumulation, called a pleural effusion. To better delineate the fluid and guide procedures, an ultrasound is often used next, as it can distinguish between free-flowing fluid and loculated, pocketed collections.
A Computed Tomography (CT) scan with intravenous contrast is the most definitive imaging study, especially in complex cases, as it provides detailed visualization of the pleural space. The CT scan helps identify loculations and the “split pleura” sign, which is the thickening and separation of the pleural membranes by the fluid, a highly specific sign of empyema. The definitive diagnostic procedure is thoracentesis, where a needle is inserted into the pleural space to aspirate a sample of the fluid.
This collected fluid is sent for a detailed pleural fluid analysis, which is essential for confirming the infection and guiding treatment. Empyema is confirmed if frank, visible pus is aspirated, or if the fluid shows specific chemical markers. Key indicators of a complicated infection include a low pleural fluid pH, typically below 7.2, and a low glucose level, often less than 60 mg/dL, reflecting the high metabolic activity of the infecting bacteria and inflammatory cells. The fluid is also analyzed for Gram stain results and culture to identify the specific organism causing the infection, which is crucial for tailoring antibiotic therapy.
Step-by-Step Treatment Options
The treatment of empyema is staged and aggressive, focusing on two main goals: eradicating the bacterial infection and completely draining the accumulated pus. Initial management begins with empiric broad-spectrum antibiotics, chosen to target the most likely pathogens. This choice is later refined to a more specific antibiotic once the pleural fluid culture results are available. Prompt drainage of the infected fluid is a mandatory intervention, as antibiotics alone are insufficient to clear the pus.
Drainage Procedures
For early-stage, free-flowing effusions (the exudative stage), a simple needle aspiration (thoracentesis) may be attempted. However, complicated effusions and frank empyema require the insertion of a chest tube (tube thoracostomy). The tube, often a small-bore catheter, is placed into the pleural space, ideally under ultrasound guidance, to allow continuous drainage.
Fibrinolytic Therapy
If the empyema is in the fibrinopurulent stage with loculations, the thick pus and fibrous strands can impede drainage through the chest tube. In these cases, intrapleural fibrinolytic agents, such as tissue plasminogen activator (tPA) combined with deoxyribonuclease (DNase), may be injected through the tube. This enzymatic therapy breaks down the fibrin and septations, improving fluid removal and attempting to avoid surgery.
Surgical Intervention
Surgical intervention is the next step if chest tube drainage and fibrinolytic therapy fail to resolve the infection or if the empyema is in the advanced organizing stage. The preferred minimally invasive procedure is Video-Assisted Thoracoscopic Surgery (VATS). VATS allows for the direct breakdown of loculations, removal of pus and debris (debridement), and stripping away of the thick pleural peel (decortication) to permit the lung to re-expand fully. For chronic or highly advanced cases, an open thoracotomy and decortication may be necessary to fully clear the infection and restore lung function.