Thoracic imaging 3

Question 1

Discuss lung patterns further?

Answer 1

• 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

Question 2

Be careful of these common errors?

Answer 2

•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)

Question 3

Discuss the mediastinum?

Answer 3

3 main bits – cranial, caudal and middle part where heart is.

Question 4

What is labelled here?

Answer 4

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

Question 5

What can be seen here?

Answer 5

Cranial mediastinum

Midline, homogenous soft band

Shouldn’t be any wider than twice the width of thoracic vertebrae

Question 6

What can be seen here?

Answer 6

Caudal mediastinum

Blue – aorta

Yellow – vena cava

Don’t normally see normal oesophagus on radiograph

Question 7

What can be seen here?

Answer 7

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.

Question 8

What can be seen here?

Answer 8

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

Question 9

Look at this barium swallow of a dog?

Answer 9

Normal appearance of dog oesophogram

• thin, can see longitudinal folds

Question 10

Look at this barium swallow pattern in a cat?

Answer 10

Change in muscle type in cat leads to this Heringbone pattern

Question 11

What can be seen here?

Answer 11

Regional megaoesophagus

Vascular ring anomaly

Dilation of oesophagus cranial to this

Question 12

Discuss pitfalls of mediastinal radiography?

Answer 12

• 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)

Question 13

What can be seen here?

Answer 13

Question 14

What is the normal size of feline heart in radiographic appearance?

Answer 14

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

Question 15

How should cardiac radiographs be interpreted in older cats?

Answer 15

Old cat

• More horizontal heart
• Prominent aortic arch, might see more of a bulge in lateral view

Question 16

Discuss how heart enlargement appears in cats?

Answer 16

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

Question 17

Hows is dogs heart like a clock face?

Answer 17

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

Question 18

What is the normal size of a dogs heart?

Answer 18

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

Question 19

Discuss breed variation in dog heart size?

Answer 19

Deep-Chested

• tall heart, narrow

Shallow-Chested

• Heart much more rounded, much wider and more sternal contact

Question 20

What is the vertebral heart score?

Answer 20

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

Question 21

What can be seen here?

Answer 21

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

Question 22

Describe this DV view of LHS enlargement?

Answer 22

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

Question 23

What can be seen here?

Answer 23

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

Question 24

What can be seen on this DV of right sided heart enlargement?

Answer 24

• Expansion of RV, particularly to RHS, increased rounding
• Line between apex and bifurcation, end up with a 3:1 cranial to that line

Question 25

Describe generalised heart enlargement in dogs?

Answer 25

* Generally big * Caudal border is displaced * Small LA bulge * Heart is tall * Wide heart * Increased rounding * Increased sternal contact

Question 26

Discuss generalised heart enlargement in dogs?

Answer 26

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.

Question 27

What is this?

Answer 27

**Microcardia** Can have a small cardiac silhouette. Hypovolaemia is an example of what can cause this

Question 28

Discuss thoracic ultrasonography?

Answer 28

* 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

Question 29

What is POCUS?

Answer 29

Point Of Care UltraSound

Question 30

What is TFAST?

Answer 30

* 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

Question 31

Outline TFAST in more detail?

Answer 31

•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

Question 32

How does a TFAST scan appear?

Answer 32

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

Question 33

Where does Vet BLUE look?

Answer 33

Looking for fluid in lungs US probe at 8 locations

Question 34

How does a normal lung compare to a wet lung on US?

Answer 34

Question 35

What can be seen here?

Answer 35

Fluid around cardiac silhouette. Pericardial effusion.

Question 36

How is US and radiography useful for diagnosing CHD?

Answer 36

* 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.

Question 37

When is further imaging useful?

Answer 37

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

Question 38

Summarise radiography and ultrasonogrophy?

Answer 38

* 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!