Thoracic imaging 3 Flashcards
Discuss lung patterns further?
- Most lung patterns are mixed – can have a combination, but don’t use this as a cop out
- Identify the predominant pattern(s) and use this to work out the most likely cause(s)
e.g.
- Bronchopneumonia may give bronchial and alveolar patterns
- Congestive heart failure may give vascular and alveolar patterns
Be careful of these common errors?
•Do not over-interpret lung radiographs!!
–consider technical/normal variants first
–if wonder if pattern present, probably not!
•Look for lesions over the diaphragm
–do not stop looking at diaphragmatic line
–Diaphragm is domed – lungs will be superimposed on here caudal to the diaphragm, so don’t look for patterns there
•Beware superimposition shadows
–e.g. blood vessels overlying ribs
•Remember progression of alveolar disease
–Bronchial à interstitial à alveolar (worsening)
–Alveolar à interstitial à bronchial (e.g. treated)
Discuss the mediastinum?
3 main bits – cranial, caudal and middle part where heart is.
What is labelled here?
Yellow arrows: cranial mediastinum
Blue arrows – can see margins between 2 lung lobes as there is a fold of mediastinum going in between the 2 lung lobes and if this margin is transverse whilst doing a lateral view, will see it
What can be seen here?
Cranial mediastinum
Midline, homogenous soft band
Shouldn’t be any wider than twice the width of thoracic vertebrae
What can be seen here?
Caudal mediastinum
Blue – aorta
Yellow – vena cava
Don’t normally see normal oesophagus on radiograph
What can be seen here?
Caudal mediastinum
Reflection of pleura – represents the left part of caudal mediastinum – its not actually in midline, its slightly over to the left – if increased opacity in this caudal mediastinum, this is where increase will be – if its more midline opacity, more likely to be right lung lobe.
What can be seen here?
Mediastinal mass/fluid
Pleural fluid as lung lobes pushed away from spine
There is a mass here – our mass effect can help – trachea is dorsally elevated and compressed, something solid doing this
Pleural fluid and mediastinal mass
Look at this barium swallow of a dog?
Normal appearance of dog oesophogram
- thin, can see longitudinal folds
Look at this barium swallow pattern in a cat?
Change in muscle type in cat leads to this Heringbone pattern
What can be seen here?
Regional megaoesophagus
Vascular ring anomaly
Dilation of oesophagus cranial to this
Discuss pitfalls of mediastinal radiography?
- The thymus is seen in young animals up to approx. 6 months. Dogs often seen in DV view. Cats seen in kittens in lateral view
- Seen as a ‘thymic sail’ on DV/VD views (esp. dogs)
- Seen as a soft tissue opacity cranial to the heart on lateral views (esp. cats)
What can be seen here?
What is the normal size of feline heart in radiographic appearance?
Normal width (DV)
- < 2/3 width of thorax
Normal short axis (lateral)
- cranial R5–caudal R7
Normal long axis (lateral)
- 2/3 height of thorax
Normal heart – roughly ovoid, in middle of thorax
How should cardiac radiographs be interpreted in older cats?
Old cat
- More horizontal heart
- Prominent aortic arch, might see more of a bulge in lateral view
Discuss how heart enlargement appears in cats?
Taller than we would expect and wider in DV view. Also abnormal shape
Enlarged atria
Caudal part relatively normal, wide shoulders – valentines heart, tells us that we have enlarged atria. In cats, cannot really get a good idea about individual chambers
Cardiomyopathy most common cause of heart disease in cats
Hows is dogs heart like a clock face?
Enlargement bulges in specific areas, can relate to individual structure of chamber enlargement in dogs – like a clock face.
In DV left side is slightly more flat
In DV right side is rounded
What is the normal size of a dogs heart?
Normal width (DV)
–< 2/3 width of thorax
Normal width (lateral)
–2.5 – 3.5 intercostal spaces wide
- Significant breed variation
Normal height (lateral – 5th rib)
–2/3 height of thorax
Discuss breed variation in dog heart size?
Deep-Chested
- tall heart, narrow
Shallow-Chested
- Heart much more rounded, much wider and more sternal contact
What is the vertebral heart score?
Add the no. of vertebrae
Suggested normal range
= 8.5 – 10.5
Breed specific values available
•Normal ranges differ between breed so always refer to this
What can be seen here?
Left-sided heart enlargement in dogs
If LHS enlarged, LV will spread caudally and also dorsally to some extent. So caudal aspect will be displaced and straight than usual
Tall heart
Describe this DV view of LHS enlargement?
DV view
General rounding and sits over the right when it should sit to left.
Line from apex to bifurcation, don’t have 1:1 ration, have a 2:1 ratio
What can be seen here?
Right-sided heart enlargement in dogs
Right ventricle will extend cranially, will increase width of cardiac silhouette and increase sternal contact
Not as much increase in height
What can be seen on this DV of right sided heart enlargement?
- Expansion of RV, particularly to RHS, increased rounding
- Line between apex and bifurcation, end up with a 3:1 cranial to that line
Describe generalised heart enlargement in dogs?
- Generally big
- Caudal border is displaced
- Small LA bulge
- Heart is tall
- Wide heart
- Increased rounding
- Increased sternal contact
Discuss generalised heart enlargement in dogs?
It is big but don’t have straight caudal border of cardiac silhouette, its very rounded
DV view – unlike generalised enlarged heart, there is no shape to it at all. This is because we aren’t looking at heart, it’s the pericardium with fluid in it.
What is this?
Microcardia
Can have a small cardiac silhouette.
Hypovolaemia is an example of what can cause this
Discuss thoracic ultrasonography?
- Useful to complement radiography or if radiography not appropriate, e.g. emergency or large animal
- Findings should always be related to clinical signs to see that they make sense.
- Limitations:
–Access – ribs can get in the way
–Air in lungs – bounces sound back
What is POCUS?
Point Of Care UltraSound
What is TFAST?
- TFAST (Thoracic Focused Assessment with Sonography for Trauma)
- Vet BLUE (Veterinary Bedside Lung Ultrasound Exam)
- Principle that you can use US in an emergency situation to get critical info
Outline TFAST in more detail?
•Five probe positions on the animals
–Chest tube site (L&R)
–Pericardial site (L&R)
–Diaphragmatico-hepatic
- Optimise probe orientation for “glide sign”
- Looking for pleural fluid of pneumothorax as a consequence of trauma usually
How does a TFAST scan appear?
Normal dog – will see ribs and shadowing deep to them
Bright lines and parallel hyperechoic lines going down – represents most peripheral part of the lung with air going in it. Bat sign – that kind of shape. Represents eyes and the most peripheral surface of the lung
With normal lung – will have pleural membrane attached to thoracic wall and lung and air in the lung, as animals breathes – these slide over each other and will see movement at peripheral hyperechoic line
No movement or gliding will happen if there is a pneumothorax for example – will NOT see the movement. You DO see this gliding in a normal dog or normal healthy parts of the lung
Where does Vet BLUE look?
Looking for fluid in lungs
US probe at 8 locations
How does a normal lung compare to a wet lung on US?
What can be seen here?
Fluid around cardiac silhouette.
Pericardial effusion.
How is US and radiography useful for diagnosing CHD?
- Plain radiographs inaccurate for diagnosis
- Angiocardiography invasive
- Ultrasound provides specific, non-invasive diagnosi
- Difficult to diagnose from plane radiographs, but you can only definitively know what is going on using echo.
–> Pictured the dog has a ventricular septal defect. Turbulent blood flow across septum to right hand side of the heart.
When is further imaging useful?
Useful where radiography and ultrasonography fail to identify cause and extent of disease, e.g.
- Surgical planning for thoracic wall lesions
- Differentiation of pleural and mediastinal masses from fluid
- Localisation of air leaks from respiratory tract
- Excellent modality for further evaluation of lung pathology, e.g. screening for metastases, bronchial foreign bodies
Summarise radiography and ultrasonogrophy?
- Radiography and ultrasonography are key modalities for the thorax and are complementary
- Good diagnostic quality radiographs are very important for the thorax, particularly positioning and phase of respiration
- Border obliteration and mass effect are important radiographic signs
- All regions of the thorax should be systematically examined
- Don’t forget peripheral structures
- Lung patterns are very useful to diagnose lung disease – even when mixed
- Remember that some lung markings are normal
- Don’t forget the mediastinum
- Remember breed variations when evaluating dog’s hearts
- Ultrasonography is a useful screening tool in acute thoracic disease, e.g. trauma, (and large animals)
- Echocardiography is very useful to diagnose heart disease, but radiography is needed to diagnose congestive heart failure
- All imaging findings should be put together to produce coherent and realistic differential diagnoses
- Don’t forget to sense check your differentials with the clinical signs!
