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Knowledge of the mediastinal contents can aid in your differential diagnosis.

Anterior mediastinum

Borders the sternum anteriorly, and the ventral cardiac surface posteriorly. Contents include the thymus, the ascending aorta, lymph nodes, internal mammary artery and vein, fat and adjacent bony structures (ribs and sternum).

Middle mediastinum

Borders the anterior mediastinal compartment anteriorly, and the anterior surface of the spine, posteriorly. Contents include the heart, proximal pulmonary arteries and veins (hila), superior and inferior vena cava, esophagus (usually not visible), vagus nerve, recurrent laryngeal nerve, trachea and proximal bronchial tree.

Posterior mediastinum

Borders the anterior surface of the spine posteriorly to the ribs. Contents include the descending aorta, the azygous and hemiazygous veins, adjacent bony structures (the spine and ribs) and spinal cord with nerve roots.

Superior mediastinum

Lower border is a horizontal line drawn from the angle of Louis posteriorly to the spine. Contents include the thyroid gland, aortic arch and great vessels, proximal portions of the vagus and recurrent laryngeal nerves, the esophagus and trachea.

Superior mediastinal (thyroid) mass


Signs of pneumomediastinum include lucencies around the great vessels, the medial border of the superior vena cava, and the azygos vein. Air may also be seen outlining the aortic arch, descending aorta, or the pulmonary arteries.

Pneumopericardium appears as a lucent area around the heart extending up to the main pulmonary arteries. A lucent line running along the inferior border of the heart and crossing the midline is diagnostic for pneumopericardium.


© Gavin Joynt, June 2005

©Charles Gomersall, January, 2018 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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