Anatomy of the Mediastinum
- Central compartment of the thoracic cavity – located between the 2 pleural sacs
- Contains most of the thoracic organs – acts as a conduit for structures traversing the thorax on their way to the abdomen
- Divided into superior and inferior parts by an imaginary line that runs from sternal angle to T4 (the transverse thoracic plane)
- Superior
- Inferior – anterior, middle and posterior
- Superior
- Aortic arch – brachiocephalic a, left common carotid a, left subclavian a
- Superior vena cava – brachiocephalic v, intercostal v, azygous v
- Vagus nerve
- Phrenic nerve
- Thymus
- Trachea and oesophagus
- Thoracic duct
- Anterior
- Thymus (in children)
- Lymph vessels and lymph nodes
- Middle mediastinum
- Heart and pericardium
- Ascending aorta
- Pulmonary trunk
- Superior vena cava
- Posterior mediastinum
- Descending aorta)
- Azygous veins
- Thoracic duct
- Oesophagus
- Splanchnic nerves
Acute mediastinitis
- Fulminant infectious process that spreads rapidly along the continuous fascial planes connecting cervical and mediastinal compartments
Etiology
- Oesophageal perforation
- Iatrogenic – balloon dilation, sclerothrapy (for variceal bleeding)
- Spontaneous – post-emetic e.g. Boerhaave syndrome
- Straining
- Post surgical – infection, anastomotic leak
- Ingestion of foreign body
- Trauma
- Erosion by cancer
- Deep sternotomy wound infection
- Oropharynx and neck infection
Clinical features
- Fever, chest pain, florid sepsis
- Dysphagia, respiratory distress
- Haemodynamic instability
- Cervical and upper thoracic crepitus; pain on inspiration
- Tachycardia, tachypnoea
Investigations
- Chest CT – shows extent of spread and guidance of drainage
Treatment
- Correct primary problem – oesophageal perforation
- Debridement/lavage
- Drainage of spreading infections
- Antibiotics
- Fluid resuscitation
- Tracheostomy in patients with descending necrotising mediastinitis
Chronic mediastinits
- Sclerosing or fibrosing mediastinitis from chronic mediastinal inflammation
- Originates in the lymph nodes
- Most frequently from granulomatous infection – histoplasmosis or TB
Clinical features
- Chronic low grade inflammation leads to fibrosis and scarring
- Leads to entrapment and compression of low pressure veins (SVC), compression of oesophagus/pulmonary arteries
Investigations
- Bronchoscopy and mediastinoscopy
- Thoracotomy – establishes benign nature of fibrosis
Treatment
- Relieve airway/oesophageal obstruction – dilate and stent airway
- Grafts – achieve vascular reconstruction