Diseases of the Mediastinum, Chest Wall and Diaphragm.

Question 1

Describe the anatomical structures that form the mediastinum

Answer 1

• The mediastinum is a true space formed by the reflections of the parietal pleura. It lies between the left and right pleural cavities
• Extends to the thoracic inlet cranially and communicates with the cervical soft tissues
• Extends to the diaphragm caudally and communicates with the retroperitoneal space via the aortic hiatus

Question 2

Mediastinum

List the important organs/structures located within the mediastinum

Answer 2

1. Trachea
2. Oesophagus
3. Heart
4. Aorta
5. Cranial and caudal vena cava
6. Thymus
7. Thoracic lymph nodes
8. Thoracic duct
9. Vagus nerves
10. Other great vessels

Question 3

Pneumomediastinum

List causes for formation of pneumomediastinum

Answer 3

1. Cervical trauma
2. Tracheal trauma (including post ET intubation)
3. Mechanical ventilation
4. Transtracheal aspiration
5. Tracheostomy
6. Central venous catheter placement
7. Oesophageal / pharyngeal rupture / tear
8. Secondary to subcutaneous emphysema
9. Lung trauma/alveolar rupture - dessecting along the pulmonary interstitium
10. Secondary to pneumoretroperitoneum

Question 4

List potential causes of mediastinitis

Answer 4

1. Oesophageal (or tracheal) perforation - mixed bacterial infection
2. Fungal infection - Histoplasma, Cryptococcus
3. Anaerobic infection - Nocardia, Actinomyces
4. Post cervical trauma / deep tissue infection
5. Extension of infection from the pericardium, pulmonary parenchyma or pleural space
6. Secondary to mediastinal neoplasia