Posterior Mediastinum Anatomy – Contents, Mnemonic, and Clinical Relevance

The mediastinum is the central compartment of the thoracic cavity, located between the two pleural sacs. It contains the heart, great vessels, esophagus, trachea, thoracic duct, lymph nodes, and nerves. Anatomically, it is divided into four compartments:

1. Superior mediastinum
2. Anterior mediastinum
3. Middle mediastinum
4. Posterior mediastinum

The posterior mediastinum lies behind the pericardium and anterior to the vertebral column. It contains vital structures that pass between the thorax and abdomen, making it an essential region for both anatomy and clinical medicine.

To remember the main structures in this space, the mnemonic DATES is widely used.

Boundaries of the Posterior Mediastinum

Anterior: Pericardium and diaphragm.

Posterior: Vertebral bodies of T5–T12.

Superior: Continuous with the superior mediastinum (above the sternal angle).

Inferior: Diaphragm.

Lateral: Mediastinal pleura (lungs on both sides).

Contents of the Posterior Mediastinum (Mnemonic: DATES)

The mnemonic DATES helps recall the structures within the posterior mediastinum:

D – Descending Aorta

• Runs along the left side of the vertebral bodies.
• Gives off bronchial, esophageal, pericardial, and posterior intercostal arteries.
• Clinical relevance: Aneurysms in the descending aorta can compress nearby structures like the esophagus, causing dysphagia.

A – Azygos and Hemiazygos Veins

• The azygos vein runs on the right, draining the thoracic wall and emptying into the superior vena cava.
• The hemiazygos and accessory hemiazygos veins run on the left, crossing over to join the azygos vein.
• Clinical relevance: Provides collateral circulation between superior and inferior vena cava in cases of obstruction.

T – Thoracic Duct

• The largest lymphatic vessel in the body.
• Begins at the cisterna chyli in the abdomen, ascends through the posterior mediastinum, and drains into the left venous angle (junction of left subclavian and internal jugular veins).
• Clinical relevance: Injury to thoracic duct can lead to chylothorax (accumulation of lymph in pleural cavity).

E – Esophagus

• Muscular tube carrying food from pharynx to stomach.
• Runs posterior to the trachea and heart, passing through the diaphragm at T10.
• Clinical relevance:
• Compression by enlarged left atrium (seen in mitral stenosis).
• Carcinoma of esophagus.
• Achalasia and esophageal strictures.

S – Sympathetic Trunks and Ganglia

• Located along the vertebral bodies.
• Contain thoracic sympathetic ganglia and splanchnic nerves (greater, lesser, and least) that innervate abdominal viscera.
• Clinical relevance: Overactivity may contribute to hypertension; sympathectomy can be used for hyperhidrosis or pain management.

Clinical Correlations of Posterior Mediastinum

1. Aortic Aneurysm – Can cause chest pain, hoarseness (recurrent laryngeal nerve compression), or dysphagia.

2. Esophageal Disorders – GERD, strictures, cancers present with swallowing difficulty.

3. Thoracic Duct Injury – Leads to chylothorax, requiring drainage.

4. Azygos System – Provides collateral circulation in SVC obstruction.

5. Posterior Mediastinal Tumors – Neurogenic tumors, lymphomas, and metastasis often arise here.

Lingula: A Quick Note

The poster mentions lingula location:

• The lingula is part of the left upper lobe of the lung.
• Functionally, it is the left-sided equivalent of the middle lobe of the right lung.
• Clinical importance: Pneumonia, bronchiectasis, and aspiration often involve the lingula due to its anatomical position.

Summary Table: Posterior Mediastinum Contents (DATES Mnemonic)

Letter	Structure	Clinical Significance
D	Descending Aorta	Aneurysm, compression of esophagus
A	Azygos & Hemiazygos Veins	Collateral circulation in SVC/IVC obstruction
T	Thoracic Duct	Chylothorax if injured
E	Esophagus	Dysphagia, carcinoma, GERD
S	Sympathetic Trunk & Ganglia	Sympathectomy, splanchnic nerve pain syndromes

Frequently Asked Questions (FAQ)

Q1. What is the easiest way to remember the posterior mediastinum contents?

Use the mnemonic DATES – Descending Aorta, Azygos veins, Thoracic duct, Esophagus, Sympathetic trunk.

Q2. Which part of the lung is the lingula?

The lingula is part of the left upper lobe, functioning as the anatomical equivalent of the right middle lobe.

Q3. Why is the azygos vein important clinically?

It provides collateral circulation between the superior and inferior vena cava, particularly in cases of blockage.

Q4. At what level does the esophagus pierce the diaphragm?

At T10 vertebral level, remembered by the mnemonic “I 8, 10 Eggs At 12” (IVC – T8, Esophagus – T10, Aorta – T12).

Q5. What happens if the thoracic duct is injured?

It leads to chylothorax, where lymphatic fluid accumulates in the pleural cavity.