Empyema

What is Empyema?

Empyema is a condition where pus accumulates in the pleural cavity, the area between the lungs and the chest wall. This pus can be identified by tests that identify culture or gram-positive matter from the fluid in the cavity. Empyema typically occurs as a complication of pneumonia but can also happen after chest surgery or trauma. In the U.S., approximately 32,000 people develop empyema each year.

This condition is serious, with about 20% to 30% of those affected either dying or needing additional surgery within a year of diagnosis. Therefore, early detection and treatment of empyema are incredibly important.

What Causes Empyema?

Around 20% of pneumonia patients may experience a condition called parapneumonic effusion which can sometimes progress into empyema – an infection of the fluid in the space surrounding the lungs. About 70% of empyema cases stem from this fluid buildup, while the remaining 30% can be linked to injuries, post-chest surgery, ruptures in the esophagus, infections in the neck, and a few cases occur independently from any prior issue – this is called primary empyema.

The types of bacteria causing empyema can differ based on whether the infection was acquired in the community (outside a hospital setting) or within a hospital. It’s also crucial to consider the patients’ existing health conditions. For empyema caught outside the hospital, gram-positive bacteria, especially those from the Streptococcus species, are most commonly found. In these cases, the presence of gram-negative bacteria is usually linked to patients with issues like alcohol abuse, acid reflux, and diabetes. On the other hand, hospital-acquired empyema often involves Staphylococcus aureus bacteria, including the drug-resistant type known as MRSA, and Pseudomonas. Also, Staphylococcus aureus is the usual culprit in empyema cases following trauma and surgery.

When advanced DNA testing is used, almost 70% of the cases may show the presence of anaerobes – organisms that can live without oxygen. But using regular testing methods, this figure might drop to 20%. This huge variation reminds doctors to treat for anaerobes, even if test results don’t show their presence.

Fungal empyema is rare but deadly when it occurs, with Candida species being the most frequently associated fungus.

Risk Factors and Frequency for Empyema

People who are more likely to get pneumonia are also more susceptible to a condition called empyema. However, some factors are specifically connected to the increased likelihood of developing empyema. These include:

• Having diabetes mellitus.
• Engaging in intravenous drug abuse.
• Being immunosuppressed, or having a weakened immune system.
• Having gastric acid reflux.
• Engaging in alcohol abuse.

Signs and Symptoms of Empyema

Empyema is a condition that can have symptoms similar to pneumonia. These symptoms include cough, fever, chest pain, and production of sputum. Patients with empyema often experience these symptoms for a pretty long time, with studies showing that on average, patients go to the doctor about 15 days after these symptoms start. During a physical exam, doctors may notice a dull sound when they tap the patient’s chest, increased vibration when the patient speaks, and a crackling sound when listening to the patient’s lungs.

However, these symptoms and exam findings are not exclusive to empyema, making it a bit hard to diagnose. That’s why if patients aren’t getting better with antibiotics, doctors should check if empyema might be the cause of their symptoms.

Doctors use a scoring system called the RAPID score to predict the likelihood of mortality within 3 months in patients with empyema. This system considers:

• The patient’s kidney function (Renal)
• The patient’s age
• Whether pus is present or absent
• Whether the infection was caught in a hospital or in the community
• The patient’s albumin levels (related to diet)

Patients with a score higher than 5 typically have worse outcomes.

Testing for Empyema

When doctors suspect empyema, a condition where pus gathers in the pleural space in the chest, they need to conduct a series of tests for a better diagnosis. Since it’s hard to identify this condition based only on symptoms, these tests are vital.

The initial test usually involves a chest x-ray, which is a straightforward and widely accessible test that can potentially show any abnormal fluid in the chest. However, it requires a significant amount of fluid to detect anything, typically around 75 ml for a side-view and approximately 175 ml for a front-view. In the x-ray images, pleural effusion (fluid in the chest) may show up as a dull area near the lung edges, depending on the size of the effusion.

If the chest x-ray hints at a possible fluid accumulation, the next step is often an ultrasound. Ultrasounds have several advantages; they are widely available, can be performed at the patient’s bedside, are more sensitive than x-rays, and can distinguish between tissue and pleural fluid. They can also guide the doctor during treatment procedures, such as inserting a chest tube. Certain signs like consistent image patterns, clear fluid with bright lines, thickening of the pleura (the membrane that surrounds the lungs), and separation of layers of the pleura by fluid, may point to empyema.

A CT scan is another useful step, particularly for patients with suspected empyema. While it can be the next step after an x-ray or ultrasound, it can also be used to help guide the doctor during treatment procedures. A contrasting agent injected into the veins can make the images clearer. Some characteristics seen on a CT scan could include thickening of the pleura, enhancement of the pleura, pockets of fluid without a drainage tube, and compartments within the fluid. The CT scan can also help assess the condition of lung tissue and position of a chest tube.

Once the thoracentesis process (removing fluid from the space between the lungs and chest wall with a needle) is complete, the fluid should be sent for analysis and culture. This helps detect the type of bacteria that may be causing the infection, although this method may not always be effective. If possible, fluid should be obtained from the thoracentesis, chest tube placements, or surgical intervention, but not from pre-existing drains.

Although pleural fluid analysis is not compulsory for diagnosing empyema, since pus, gram-positive bacteria, or cultures can confirm the diagnosis, it is still recommended to carry out an analysis on all pleural fluids.

Treatment Options for Empyema

Just like any other infection, it is crucial to immediately begin antibiotics and try to control the root source. For empyema, a type of lung infection, treatment typically includes both medications and sometimes surgery. A specific mixture of antibiotics is used to provide broad coverage against the possible bacteria causing the infection.

For draining the buildup of pus in the lungs, the common method is tube thoracostomy. This involves inserting a tube into the pleural cavity, the area around the lungs. The size of the tube doesn’t impact the patient’s outcome or survival rate, but larger tubes often cause more pain, so doctors generally prefer using smaller tubes. The correct positioning of the tube is crucial and is usually checked by an X-ray or CT scan. If the patient doesn’t show signs of improvement within 24 hours, it often means that the tube was poorly positioned or is blocked.

A special medication has been used for about 60 years to help break down and drain the pus from within the lungs. However, the usage of this medication, alone or in combination with others, hasn’t shown improved survival or reduced need for surgery. Therefore, it’s not typically a part of standard treatment.

Surgery is usually a last option. Its primary aim is to drain the pus from the lungs and help them expand properly. The first step in surgical intervention is usually video-assisted thoracotomy (VATS), a minimally invasive procedure with several benefits including less blood loss and pain for the patient, improved lung function, shorter hospital stay, and reduced chances of mortality after a month. However, in some cases, such as uncontrolled bleeding or failure in evacuating the cavity or lung expansion with VATS, a more invasive open-thoracotomy might be needed.

After the acute phase, some patients may develop fibrosis or scarring in the lungs, leading to breathing issues and limited exercise capacity. In such cases, decortication, a surgical procedure to remove the fibrous layer, may help alleviate these symptoms. Nevertheless, this consideration is made after carefully evaluating the patient’s condition.

What else can Empyema be?

• Pneumonia
• Heart failure
• Pulmonary infarction (blockage of blood flow to the lungs)
• Sequestration (lung tissue becomes isolated from the rest of the lung)

Possible Complications When Diagnosed with Empyema

Fibrothorax and respiratory distress are two major health concerns. In simple terms:

• Fibrothorax: A condition in which the space between the lung and chest wall gets filled with fibrous tissue, making the lung unable to fully expand.
• Respiratory distress: A state of difficult or labored breathing, which often signals a serious health problem.