The mediastinum Flashcards
What are the three main parts of the mediastinum?
Three main parts:
- Cranial
- Middle
- Caudal
What are the normal size parameters for the cranial mediastinum?
Normal size:
- No more than 2x width of thoracic vertebral bodies on the VD
- Slightly larger than the trachea
What are the normal cranial mediastinal structures that should be seen?
Seen:
- Trachea should be seen
No seen:
- Oesophagus not seen
- Major vessels should not be seen
- Lymph node silhoutte not seen
- Thymus silhoutte
What is the effect of fat on the mediastinum?
- Fat ⇒ widened diffusely
Evaluate the dimensions of the cranial mediastinum below:
- Normal - it is not more than 2x the width of the thoracic bodies on the VD
What structures are in the middle and caudal mediastinum?
Middle mediastinum:
- Heart ventrally
- Aorta
- Oesophagus
- Caudal trachea and bifurcation
- Lymph nodes
- Ventral spine muscles dorsally
Caudal mediastinum:
- Aorta
- CaVC
- Oesphagus
- Ventral mediastinal deflection
What are the signs that show mediastinal shift?
- Heart shifted to thoracic wall
- Diaphragm cranially displaced
- Decreased volume in hemithorax
****make sure thorax is not rotated ⇒ false interpretations
What are the four main causes of mediastinal shift?
- Displacement
- Dependancy atelectasis
- Adhesions
- Loss of lung volume
Describe the changes in the image below and make a radiographic diagnosis:
- The thorax is not significantly rotated so can proceed with interpretation
- Mediastinal shift to the right
- Right diaphragm is flat and cranially positioned
- Right lung volume is decreased
- Marked increase in soft tissue opacity and a reduction in gas opacity in the affected lungs
Describe the normal appearance of the trachea that is seen:
- Normal tracheal wall is difficult to see - opacity slightly > adjacent soft tissues as cartiladge
- Position enters thoracic inlet approximately 1/3 to 2/3
For the images below - state which view is a right and which is a left lateral:
- Top: R-lateral (more curve in trachea and narrower heart)
- Bottom: L-lateral (less curve in the trachea and heart appears more like a box shape)
What are the normal tracheal range reference sizes for:
- Non-brachycephalic breeds
- Non-bulldog breeds
- Bulldogs
- Non-brachycephalic breeds - 20% diameter/TI
- Non-bulldog brachycephalic breeds - 16%
- Bulldogs - 13% of TI
What are the major diagnostic differentials for a trachea of reduced size?
- Collapsing trachea - dynamic or static regions
- Hypoplasia - diffuse
- Severe tracheitis diffuse
- Focal decrease in size - stenosis, FB, mass
Describe the trachea that is shown below:
Hyoplastic trachea
Describe the change shown in the trachea below and provide three Ddx for this change:
Focal decrease in size:
- Stenosis
- FB
- Mass
What is the most likely cause for the radiographic findings below:
- Tracheal stripe sign
- Increased visibility of the tracheal walls as surrounded by gas
⇒ Probably anaesthesia - only mild
What structure is causing displacement of the trachea in this picture?
The oesphagus is causing displacement (trachea being directly ventrally)
What structure is displacing the trachea in the image below?
- The heart is displacing the trachea in the image below
Name the structures that are shown in the image below and make a diagnosis:
- Purple = the tracheal walls (inner and outer margins)
- Light blue = thoracic aorta
- Yellow = large vessels of the mediastinum
- Green = the longus colli muscle
Diagnosis: pneumomediastinum
Name the two findings that are shown below (two purple arrows) and provide an interpretation:
- Increased opacity of the mediastinum and also trachea has been displaced dorsally
- Possible differentials could include a mediastinal mass (focal) or fluid (diffuse)
Name the structure that is shown below and provide some Ddx for it:
- Minimal amount of gas situated just cranial to tracheal bifurcation (oesphagus)
- Ddx: Excited, aerophagia, dyspnoea (note: mild dilation occurs under a GA)
Is the oesphogram shown below normal or abnormal?
Oesphogram shown below can be considered normal
Comment on the significance of the finding below given that the animal was just under general anaesthesia:
- The oesphagus is mildly distended but quite normal given the animal was just under GA
For the image below:
- Describe the findings
- Make a radiographic diagnosis
- Provide a list of differentials for the presentation
1. Abnormalities:
- Tracheal stripe sign (green)
- Thin soft tissue lines to the diaphragm (walls of the oesphagus)
- Light blue = accentuation of the longus colli muscle
- Yellow = aspiration pneumonia (right middle lung lobe)
2. Radiographic diagnosis:
- Megaoesphagus with secondary aspiration pneumonia (neuromuscular dysfunction) - generalised enlargment with poor motility
3. List of differentials:
- Myasthenia gravis
- Idiopathic
- Myositis
- Polyneuropathy
- CNS
- Oesphagitis
Name the abnormality that is shown in the image below:
- Mass filling defect - caudal thoracic oesophagus
Name the abnormality that is demostrated in the image below:
Vascular ring anomaly - focal enlargement cranial to the heart base
