Causes of Mediastinal Shift Flashcards
How much of the heart is normally right of the midline?
A third
What is the mediastinum?
Consists of blood vesselsm trachea, oesphagus, thoracic duct, phrenic nerves and the thymus
How can you tell if the mediastinum has moved?
The heart may also move, so that a third is no longer on the right hand side of the midline
What parts of the lung that can normally be seen on X-Ray can be obliterated by disease?
Fissures - major and minor
Hila - left is higher than the right
Junction lines
Paraspinal lines should be less than 10mm
Which hila is higher?
Left - superior to the heart
Name some causes of bilateral adenopathy.
Sarcoidosis
Lymphoma
TB
Malignancy - most likely
What is the distinctive feature of mediastinal adenopathy?
Mediastinal nodal masses
Does lobar collapse normally cause mediastinal shift?
No
Name a cause of upper lobe collapse.
Tumour presence - should be the primary suspect
How can right upper lobe collapse be identified on an X-Ray?
Opacification of the right upper zone
Displacement of the horizontal fissure superiorly
Bulging of fissures medially - Golden’s reverse sign
Trachea deviated towards the affected side (the right)
When a lobe collapse (upper or lower) is identified, what further investigation should be done?
History Examination Blood tests CT Bronchoscopy
How can left upper lobe collapse be identified on an X-Ray?
Opacification in the left upper zone
Displacement of the oblique fissure superiorly
Bulging of fissures medially - Golden’s
reverse sign
Trachea deviated towards the affected side (the left)
May see a veil like opacification of the left hemithorax and aerated left apex due to expanded left lower lobe
- may see elevated left hemidiaphragm
What is the most important cause of lower lobe collapse?
Tumour - although other causes are possible
How can left lower lobe collapse be identified on an X-Ray?
Wedge shaped, triangular opacification behind the left heart border (sailing boat sign)
Displacement of the left hilum inferiorly
Obliteration of the left hemidiaphragm
Hyperlucent remaining left lung
What are the causes of a hyperlucent lung?
Technical causes (rotation) Chest wall/pleural abnormalities Vascular problems (PTE) Surrounded by ring shadows (bullae)
If you see a hyperlucent lung with mediastinal shift, what is the diagnosis?
Tension pneumothorax
How can a pnuemothorax be diagnosed on X-Ray?
Identification of the pleural line (visceral) - it will be folded into the lung area
Bullea
Most easily seen on an expiratory film
Deep costophrenic angle
Increased clarity of the mediastinal border
Depression of the diaphragm and visualisation of the undersurface of the heart
How can a left tension pneumothorax be identified on a chest X-Ray?
Depression of the left hemidiaphgram (increased pressure in chest cavity)
Tracheal displacement to the right
Hyperlucency of the left hemithorax
Small left basal pleural effusion (loss of the costophrenic angle)
Displacement of the heart to the right (more than a third is visible to the right of the midline)
Pleural line can be seen
What are the possible complications of a pneumothorax?
Haemothorax
Tension
Adhesions - slow re-expansion or bleeding if they tear
Delayed expansion adhesions lead to airway obstruction
Re-expansion oedema
What is a pleural effusion?
Fluid in the pleural space
- fluid is normally generated by the parietal layer and absorbed by the visceral layer
What are the types of fluid that can cause pleural effusion?
Transudate Exudate Blood - haemothorax Chyle - chylothorax Mixed
How can a pleural effusion be recognised on an X-Ray?
Blunting of the costophrenic angle
Some of the lung has become white
Massive effusion
- there is mediastinal shift away from the white lung
- diaphragmatic inversion (more common on the left)
What are the possible causes of a pleural effusion?
Hypoproteinaemia - cirrhosis, nephrotic syndrome
Cardiovascular - CCF, constrictive pericarditis or SVCO
Neoplasm - bronchial, metastases, lymphoma or mesothelioma
Infection - bacterial, fungal or viral
Trauma
Thromboembolism
Inhalation - asbestos
Collagen vascular disease - SLE, rheumatoid arthritis
Subdiaphragmatic disease - pancreatitis, subphrenic abscess
What is the most common cause of a massive pleural effusion?
Malignant disease Heart failure Cirrhosis TB Empyema Trauma
What are the most common causes of opacification of the hemithorax?
Pleural effusion Consolidation Collapse Massive tumour Fibrothorax Combination Pneumonectomy Lung agenesis
How does mediatstinal shift occur after a pneumonectomy?
The heart moves into the space where the lung was, taking the mediastinum with it.
The heart can’t be seen as it is oscured by the opacification of the pneumonectomy
How can a subpulmonary effusion be recognised on a chest X-Ray?
Free fluid collects under the lung
- becomes generalised around 250mls
Hemidiaphragm is high and appears opaque
Best seen on a lateral decubitas film
How can fluid accumulation in the fissures of the lung be caused and identified on X-Ray?
Most commonly caused by heart failure or a phantom
tumour
The lung will have sharp margins, with a biconvex tail along the fissure
What are the causes of a white lung with mediastinal shift towards the dense side?
Collapse
Post pneumonectomy
Lymphangitis carcinomatosa
Pulmonary agensis and hypoplasia
What are the causes of a white lung with a central mediastinum?
Consolidation
Pleural effusion - small
Mesothelioma
What are the causes of a white lung with mediastinal shift away from the dense side?
Pleural effusion - large
Diaphragmatic hernia
