Posterior Mediastinum
The posterior mediastinum is an anatomical region between the lungs in the chest that can sometimes be mentioned in radiology reports. When your doctor orders imaging of this region, they’re looking for specific information that could explain your symptoms or monitor existing conditions. Understanding what the posterior mediastinum is and how it appears on imaging can help you better understand your radiology reports.
What Is the Posterior Mediastinum?
The mediastinum is the central compartment of the chest cavity, situated between the lungs. It contains the heart, major blood vessels, esophagus, trachea, thymus, and lymph nodes. This area is divided into anterior (front), middle, and posterior (back) sections. The posterior mediastinum specifically refers to the area behind the heart and in front of the spine.
This region houses important structures:
- The descending thoracic aorta
- The esophagus
- The azygos and hemiazygos veins
- The thoracic duct
- The sympathetic chain
- Lymph nodes
- Nerves, including the vagus nerve
Why Doctors Order Posterior Mediastinum Imaging
Doctors may request imaging of the chest and posterior mediastinum for various reasons:
- Persistent chest pain or discomfort
- Difficulty swallowing (dysphagia)
- Unexplained cough or hoarseness
- Abnormal findings on chest X-rays
- Suspected tumors or masses
- Monitoring known conditions like aortic aneurysms
- Evaluation after trauma or injury
- Follow-up for previous surgeries in the chest area
Common Imaging Techniques for the Posterior Mediastinum
Several imaging modalities can visualize the posterior mediastinum, each with specific advantages:
CT Scans (Computed Tomography)
CT scans are the most commonly used imaging technique for the posterior mediastinum. These scans produce detailed cross-sectional images that clearly show the anatomical structures.
CT scans of the posterior mediastinum can:
- Identify masses or tumors
- Detect enlarged lymph nodes
- Visualize aortic aneurysms or dissections
- Show abnormalities in the esophagus
- Evaluate abnormalities in soft tissue structures
CT scans are quick, widely available, and provide excellent detail of both bone and soft tissue structures, making them ideal for evaluation of posterior mediastinal abnormalities.
MRI (Magnetic Resonance Imaging)
MRI provides superior soft tissue contrast compared to CT scans, making it particularly useful for examining certain posterior mediastinal conditions. An MRI may be ordered when:
- More detailed evaluation of soft tissues is needed
- Neurogenic tumors are suspected
- Vascular abnormalities require further investigation
- The patient cannot undergo CT scanning
- Doctors need to distinguish between fluid, blood, and solid masses
MRI scanning of the posterior mediastinum takes longer than CT but can provide valuable additional information in complex cases.
PET-CT (Positron Emission Tomography)
PET-CT combines structural imaging from CT with functional metabolic information. This combination is particularly useful for:
- Detecting and staging cancers
- Evaluating lymphoma involvement in the posterior mediastinum
- Helping to determine if a mass is malignant or benign
- Monitoring response to cancer treatment
- Identifying areas of infection or inflammation
PET-CT is especially valuable in oncology settings where doctors need information about both the location and metabolic activity of abnormalities. Higher levels of metabolic activity are found in inflammation and cancer.
Common Findings in the Posterior Mediastinum
Radiologists may identify various abnormalities in the posterior mediastinum that require attention:
Neurogenic Tumors
The most common posterior mediastinal masses are neurogenic tumors, which develop from nerve tissue. On imaging, they typically appear as well-defined, round or oval masses adjacent to the spine.
In my practice, these findings often indicate the need for further evaluation with MRI, as this imaging modality can better characterize the relationship between the tumor and surrounding nerve structures, which is important for surgical planning.
Esophageal Abnormalities
The esophagus runs through the posterior mediastinum, and imaging may reveal:
- Esophageal cancer
- Hiatal hernias
- Achalasia (a motility disorder)
- Diverticula (pouches in the esophageal wall)
- Varices (enlarged veins)
These findings are often better evaluated with specialized techniques like barium swallow studies in conjunction with CT or MRI.
Vascular Abnormalities
The posterior mediastinum contains major blood vessels that can develop abnormalities such as:
- Aortic aneurysms (bulging of the aortic wall)
- Aortic dissection (tearing of the inner layer of the aorta)
- Aberrant blood vessels
- Azygos vein enlargement
Some of these vessel abnormalities usually require urgent treatment, especially in cases of dissection or rapidly expanding aneurysms.
Lymphadenopathy
Enlarged lymph nodes (lymphadenopathy) in the posterior mediastinum may indicate:
- Infections
- Cancer that has spread from elsewhere in the body
- Lymphoma
- Inflammatory conditions like sarcoidosis
The pattern, size, and distribution of enlarged lymph nodes can provide important diagnostic clues about the underlying condition.
Understanding Your Radiology Report
When reading a radiology report that mentions the posterior mediastinum, you might encounter terminology like:
- “No posterior mediastinal masses” – This is good news indicating no abnormal growths were found.
- “Posterior mediastinal lymphadenopathy” – This indicates enlarged lymph nodes requiring further investigation.
- “Descending thoracic aortic aneurysm” – This describes an abnormal bulging of the major artery in the posterior mediastinum.
- “Neurogenic tumor in the right posterior mediastinum” – This suggests a growth arising from nerve tissue.
Radiologists typically note the posterior mediastinum when evaluating for potential sources of chest symptoms or when following known conditions. Their descriptions of this area help guide treatment decisions and surgical approaches if intervention is needed.
Conclusion
The posterior mediastinum is an important area within the chest that contains structures like nerves, blood vessels, lymph nodes and the esophagus. When this region appears on your radiology report, it can mean that an abnormality is either detected by the interpreting radiologist or is being followed by your doctor.
Imaging tests like CT, MRI, and PET-CT help with making an accurate diagnoses and to develop appropriate treatment plans. If you have questions about findings in your posterior mediastinum, don’t hesitate to discuss them with your doctor. Your doctor can best explain the significance of these findings in the context of your overall history and suggest appropriate next steps.
References