Empyema is a serious chest infection characterized by the accumulation of pus within the pleural space, the thin area between the lungs and the chest wall. Computed Tomography (CT) scans offer a powerful imaging technique to visualize these complex chest conditions. This article explains how CT scans are utilized in identifying, diagnosing, and guiding the management of empyema.
Understanding Empyema and CT Imaging
This infection often arises as a complication of pneumonia, though it can also result from chest trauma or surgery. The accumulating infected fluid, sometimes a pint or more, can press on the lungs, leading to symptoms like shortness of breath and chest pain.
A CT scan is a medical imaging method that uses X-rays and computer processing to create detailed cross-sectional images of the body. Unlike traditional X-rays, which produce a single flat image, CT scans generate multiple “slices” or views, offering a comprehensive look at internal structures. This capability makes CT scans particularly helpful for examining chest conditions, allowing healthcare providers to visualize organs, bones, soft tissues, and blood vessels.
How CT Identifies Empyema
CT scans provide specific visual characteristics that aid in identifying empyema. One common finding is the presence of fluid collections within the pleural space, which may appear with high attenuation values, indicating pus or debris. The pleura, the membranes lining the lungs and chest cavity, often appear thickened and show increased enhancement after the injection of contrast material.
A highly suggestive sign of empyema on a CT scan is the “split pleura sign,” where both the visceral (lung-covering) and parietal (chest wall-lining) layers of the pleura are thickened and separated by the fluid collection. The fluid itself can be loculated, meaning it is divided into smaller pockets by fibrous septations. The presence of air-fluid levels or gas bubbles within the pleural collection strongly indicates an empyema caused by gas-producing organisms. These distinct features help differentiate empyema from other types of pleural effusions.
The Role of CT in Empyema Management
Beyond initial diagnosis, CT scans are important for the management of empyema. The imaging helps assess the extent of the infection, providing information on the size and location of the pleural fluid collection. It can also reveal complications like a bronchopleural fistula, an abnormal connection between the airways and the pleural space.
CT scans are used to guide interventional procedures, such as the placement of drainage catheters. By precisely identifying the optimal site for drain insertion, CT guidance helps ensure effective removal of pus from the pleural space. Repeat CT scans can monitor the effectiveness of treatment, showing whether the fluid collection is decreasing and if any new complications are developing. This allows healthcare providers to adjust treatment strategies as needed.
What to Expect During an Empyema CT
You may be asked to avoid eating or drinking for a few hours before the scan, especially if a contrast dye is used. Before the scan, you will likely change into a hospital gown and remove any metal objects or jewelry that could interfere with the images.
A technologist will start an intravenous (IV) line, usually in your arm, through which a contrast material may be injected. This contrast helps highlight certain structures on the scan, making findings clearer. During the injection, you might feel a warm sensation throughout your body or a metallic taste in your mouth, which are normal and temporary effects. You will lie still on a table that slides into the CT scanner, a large, doughnut-shaped machine. The technologist will provide instructions, including brief breath-holds, to ensure clear images. The actual scanning usually takes only a few minutes, though the entire appointment may last around 20-30 minutes, allowing for preparation and post-scan observation.