Thorax Practical Flashcards
what are the 4 radiographic views that can be used to assess the thorax of dog and cat
- right lateral
- left lateral
- dorsoventral
- ventrodorsal
which views are most commonly used in practice
right lateral and dorsoventral
how is the animal placed for right lateral view
right lateral recumbency and beam passes from left to right
how is the animal positioned in left lateral views
left lateral recumbency and beam passes from right to left
how is the animal positioned in a dorsoventral view
sternal recumbency and beam passes from dorsal to ventral
how is the animal positioned for ventrodorsal views
dorsal recumbency and beam passes from ventral to dorsal
Can you remember what the different options might be for restraining animals for thoracic radiography?
Unconscious – general anesthesia
Conscious – sedation / unsedated is animal quiet or sick
Physical restraint - positioning aids eg sandbags, ropes etc
Manual restraint – held by person in protective lead lined clothing
In the UK, which of these options would only be indicated in the case of an animal with severe dyspnoea / respiratory distress and why is this the case?
Manual restraint – risk to human from ionising radiation should be minimised and permitted dose when performing veterinary radiography is zero so need very good reason to do this in the UK.
How do you think the presence of dyspnoea / respiratory distress would affect the quality of the resulting radiograph?
Poor quality image due to movement blur.
Sedating/anaesthetising animals with respiratory distress may be contraindicated but the converse argument would be that at least you would be more likely to get diagnostic radiographs!
Why is it important to pull the forelegs as far forward / cranially as possible when radiographing the thorax?
To remove the triceps muscle mass from overlying the cranial region of the thorax on the radiograph.
The heart appears to be a different shape in the right and left lateral views? Why do you think this is the case?
The heart is fixed in position at the base by the great vessels but the apex is mobile and so in lateral recumbency the apex of the heart moves with gravity.
The apex naturally sits to the left so when the animal is in right lateral recumbency the apex falls towards midline and is held there so the heart is projected “side on”.
In L Lat views, the apex falls towards the L thoracic wall so the heart is projected more along its length
The heart appears to be a different shape in the Dorsoventral and Ventrodorsal views? Why do you think this is the case?
The heart is fixed in position at the base by the great vessels but the apex is mobile and so in dorsal recumbency (Ventrodorsal view) the apex of the heart falls with gravity towards the vertebral column and so the heart appears elongated.
In ventral recumbency, (Dorsoventral view) the heart has a more natural, upright position in the thorax with the apex located towards to sternum and therefore appears more rounded.
There is also increased contact with the diapgrham in this view
Why do you think the blood within the heart is not visible on radiographs?
Fluid produces the same opacity as soft tissue on radiographs.
The fluid and myocardium are superimposed onto each other.
What is the vertebral heart score in this dog and how would you assess its heart relative to the intercostal spaces and height of the thorax? Is this dog normal?
VHS approx 12. Heart slightly greater than 2/3 height and width of thorax. Suggested slightly enlarged
When assessing a dog with cardiac abnormalities what information does radiography provide about the heart?
Overall Size, Shape, Specific chamber enlargement, Location, Evidence of congestive failure (pulmonary oedema, etc)
What information does radiography not provide about the heart?
Internal structures of heart (valve leaflets, ventricular septum, etc) myocardial function or valve incompetence
Why do the lung lobes appear dark on radiographs?
Air filled therefore do not attenuate the X-Ray bean resulting in increased blackening of the film – described as being radiolucent
Why are the blood vessels in the lung visible?
They are a combination of fluid (blood) and soft tissue (vessel walls) and so are radio-opaque (grey) while the surrounding lung is air filled and therefore radiolucent (dark)
Why do you think the lungs look clearer in the L lateral view of one dog than the R lateral view of the other?
The lungs are better aerated in the L Lat view and therefore there is better contrast between the air filled lung and the vascular structures of the lungs and also the other soft tissue structures of the thorax.
This could be due to a number of reasons – stage of respiratory cycle image was taken at, GA v conscious dog, presence of respiratory disease, breed (eg. Brachycephalic) etc
What anatomical features allow you to recognise this as a cat and not a dog?
Clavicle, square olecranon, long fine vertebral bodies etc
What is the triangular arrow pointing to and what does this tell you about the cat?
Endotracheal tube – cat was under GA
Why are all the abdominal structures so well delineated in this cat? Which organs can you recognise and what is labelled *?
Presence of intraluminal fat – radiolucent areas between organs.
Falciform fat
Liver, stomach, left and right kidneys, small and largeintestine
what are the lines demonstrating
crura of the diaphragm parallel in right lateral view
heart long and in contact with sternum
what is demonstrated by the lines
crura of diaphragm V shaped left lateral
heart shorter, rounded and less contact with sternum
what are the lines demonstrating
2 bulges to diaphragm
heart rounded
increased contact between heart and diaphragm
what is demonstrated by the lines
3 subtle bulges to diaphragm
heart elongated
less contact between diaphragm and heart
what are the structures shown
- left ventricle
- left atrium
- right ventricle
- right atrium
- aorta
- caudal vena cava
what are the structures shown
- left ventricle
- left atrium
- right ventricle
- right atrium
- aorta
- caudal vena cava
Why does the presence of pulmonary oedema cause an increase in opacity of the lung?
Fluid replaces air in the alveoli therefore lung no longer radiolucent. Fluid attenuates the beam producing areas of soft tissue opacity.
How would you go ab out obtaining more information about the valvular and myocardial function in this dog?
Perform an ultrasound examination / echocardiography
what are the structures
- trachea
- carina
- bronchi
- a. left cranial lung lobe - cranial part
- b. left cranial lung lobe - caudal part
- left caudal lung lobe
- right cranial lung lobe
- right middle lung lobe
- right caudal lung lobe
- accessory lung lobe
- pulmonary blood vessels
what are the structures numbered
- trachea
- carina
- bronchi
- a. left cranial lung lobe - cranial part
- b. left cranial lung lobe - caudal part
- left caudal lung lobe
- right cranial lung lobe
- right middle lung lobe
- right caudal lung lobe
- accessory lung lobe
- pulmonary blood vessels
the trachea is superimposed onto the vertebral column
what structures are numbered
- trachea
- carina
- bronchi
- pulmonary blood vessels
describe the heart shape using the clock analogy and what goes where
12-3: left atrium
3-5: left ventricle
5-8: right ventricle
8-10: right atrium
10-12: great vessels
what is the heart shape locations in the clock analogy
Which view is the mass most clearly visible in? How can you recognise this view?
left lateral view
L marker on radiograph! Also crura of diaphragm divergent , heart upright and less contact with the sternum etc
When a dog is positioned in lateral recumbency for any length of time what do you think happens to the 2 different sides of the lung?
The lower lung becomes compressed and congested therefore is smaller and more opaque. The uppermost lung increases in size and hyperinflates to compensate and so becomes darker.
When a dog is positioned in lateral recumbency for any length of time what do you think happens to the 2 different sides of the lung?
The lower lung becomes compressed and congested therefore is smaller and more opaque. The uppermost lung increases in size and hyperinflates to compensate and so becomes darker.
Bearing this in mind, can you work out which side of the lung this dogs mass is located in?
In a left lateral view the left side of the lung is nearest the table and becomes compressed. It therefore contains less air than normal so soft tissue masses would not be as well delineated.
The right side of the lung is uppermost and so is hyperinflated. This means that there is good contrast between the air filled lung and the soft tissue mass.
The fact that the mass is more clearly visible in the left lateral view therefore means that it is located in the right lung.
Why do you need to clip the dog and apply ultrasound gel before starting the scan?
Remove air from between the transducer and skin surface to allow penetration of the beam and therefore produce good quality images
The heart is located within the bony ribcage. How do you think we can overcome the fact that the ultrasound beam cannot penetrate through bone in order to scan the heart?
Use a transducer with a small face or area of contact with the skin surface and direct the beam through the intercostal spaces between the ribs. Sector and microconvex transducers are both appropriate for scanning the heart.
The heart is also surrounded by the air filled lungfield which again the ultrasound cannot penetrate through. What anatomical feature of the lungs can we use to allow the ultrasound beam to reach the heart without air filled lung getting in the way?
The cardiac notch
Echocardiographic image quality is best when the dog is in lateral recumbency and the transducer is placed against the dependent thoracic wall. Why do you think this might be the case?
The cardiac apex is mobile and falls under gravity towards the dependent thoracic wall. It falls into the cardiac notch and pushes the lung out of the way. The lower lung also becomes congested and reduces in size so the size of the cardiac notch becomes bigger and there is less interference from the lung.
Do you think we would we be able to image the heart from the uppermost thoracic wall? Explain your answer
It is possible but image quality is poor because the heart falls away from the transducer. The uppermost lung also hyperinflates therefore the cardiac notch becomes smaller and there is more interference from the lung.
How do you know where to place the transducer to start the scan?
Feel for the apical beat and place the transducer over it
The orientation of the heart is different in the images taken from the right and left sides of the thorax. Why do you think this is the case?
In right lateral recumbency the apex of the heart that usually sits to the left falls towards midline and this allows the beam to image the heart from the side.
In left lateral recumbency the apex of the heart falls further to the left (towards the transducer) so the heart becomes more vertically orientated and this allows the beam to image the heart along its length from apex to base.
Which side of the heart is in the near field (top) of the ultrasound image in the right thoracic views?
Right side – the nearer to the transducer a structure is the further up the image it is displayed and when imaging from the right thoracic wall the right side of the heart is nearest to the transducer.
When assessing a dog with cardiac abnormalities what information does echocardiography provide about the heart?
Chamber size, Myocardial Function, Blood flow and leakage through valves, Disease of internal cardiac structures
What information does it not provide in cases with left sided cardiac failure?
Evidence of congestive changes in the lungs (pulmonary oedema, etc)
In cases with right sided cardiac failure, which abdominal organ might you find changes in on ultrasound examination?
Liver – enlargement of hepatic veins due to congestion within the caudal vena cava (back pressure from right atrium)
In the left thoracic views in which direction is blood flowing relative to the transducer? Do you have any idea why these views are therefore ideal for measuring blood flow through the heart?
Flow through the atrio-ventricular valves is directly TOWARDS the transducer and flow through the aortic valve is directly AWAY FROM the transducer.
Doppler ultrasound most accurately records the speed of flow when it is directly towards or away from the transducer - this is why speed cops will try to position themselves either in front of or behind the flow of traffic and not to the side.
identify the structures of right short axis view
- left ventricle
- left atrium (2* left auricular appendage)
- right ventricle
- right atrium
- left ventricular free wall
- papillary muscles
- interventricular septum
- interatrial septum
- mitral/bicuspid/left atrio-ventricular valve
- tricupsid valve/right atrio-ventricular valve
- aorta
- aortic/semilunar valve
- pulmonic trunk
- pulmonic valve
- chordae tendinae
what are the numbered structures shown in the right short axis view
- right ventricle
- left ventricular free wall
- interventricular septum
- mitral/bicuspid/left atrio-ventricular valve
what are the structures shown in right - short axis view
- left atrium (2* left auricular appendage)
- right ventricle
- aorta
- pulmonic trunk
- pulmonic valve
what are the structures on the right long axis
- left ventricle
- left atrium (2* left auricular appendage)
- right ventricle
- right atrium
- left ventricular free wall
- interventricular septum
- interatrial septum
- mitral valve
- tricuspid valve
what are the structures in the right - long axis
- left ventricle
2*. left auricular appendage
- right ventricle
- right atrium
- left ventricular free wall
- interventricular septum
- tricuspid valve
- aorta
what are the structures on the left -4 chamber view
- left ventricle
- left atrium
- right ventricle
- right atrium
- interventricular septum
- mitral valve
- tricuspid valve
This radiograph was obtained by injection of radio opaque fluid into the arterial system (post mortem).
Distinguish between the Common carotid a. and the Vertebral a. in this angiogram.
Both the Common carotid a.a and the Vertebral aa. supply arterial blood to the head region
A: common carotid
B: vertebral artery
identify the vessels
1= aortic sinuses
2 = aortic arch
3= brachiocephalic trunk
4= left subclavian a.
5= common carotid aa.
6 = vertebral a.
7= superficial cervical a.
8a= right subclavian a.
8= axillary a.
9= internal thoracic a.
10= costocervical a.
11= descending aorta
12 = intercostals aa.
13.= celiac artery
14= Cranial mesenteric
Which major arteries arise from the brachiocephalic trunk in the dog?
Right and left common carotid aa and the right subclavian a. The left subclavian a. Arises independently from the aorta just distal to the origin of the brachiocephalic trunk. Note that in some of the larger species all four arise directly from the brachiocephalic trunk.
Which four major arteries arise from the Right Subclavian artery in the dog before it continues as the axillary artery into the forelimb?
In order these are 1.vertebral a. Costocercial a. Superficial cervical a. And directly opposite this in the internal thoracic a.
identify the vessels
- Brachiocephalic Trunk
- Left Subclavian Artery
- Right Axillary Artery
- Right Vertebral Artery
- Right Common Carotid Artery
- Deep Circumflex Iliac Artery
- Caudal Mesenteric Artery
Which of these arteries if any is/are unpaired?
Caudal mesenteric artery
identify the vessels
- Vertebral a.
- Costocervical a.
- Int thoracic a.
- Superficial cervical a.
- Common carotid a.
- Cranial thyroid a. (supplies larynx and pharynx)
- Coronary a. (left)
- Bronchioesophageal a.
- Celiac a.
- Cr mesenteric a.
- Ext. iliac a.
- Int. iliac a
- Median sacral a.
identify the vessels
- Cranial mesenteric artery
- Renal arteries
- External iliac arteries
- Internal iliac arteries
- Common carotid arteries
identify the vessels
- Cranial vena cava
- Azygos vein
- Internal thoracic vein
- Cephalic vein
- External /internal maxillary veins
- Subclavian vein
- Costocervical/vertebral trunk
What criteria might you use to differentiate between this venogram and angiogram?
The external jugular vein are very large and are superficial compared to the common carotid aa. The vertebral aa’s. are clearly distinguishable in the angiogram
List the contents of the umbilical cord at the umbilicus (foetal body wall) and give their function.
Umbilical arteries (paired) blood form foetus to placenta (deoxygentated)
Umbilical vein (single) blood form placenta to foetus (oxygenated)
Urachus - the excretory fluid/waste from the developing bladder via umbilical cord to the allantoic sac where it is stored
The ductus arteriosus is particularly prominent in this specimen. Name the two vessels this arterial structure link and what is its functional significance?
The pulmonary trunk and the aorta.
Blood diverted away from non-functioning lungs
list the contents of the umbilical cord at the umbiliculs (fetal body wall) and give their function
Umbilical arteries (paired) blood form foetus to placenta (deoxygentated)
Umbilical vein (single) blood form placenta to foetus (oxygenated)
Urachus - the excretory fluid/waste from the developing bladder via umbilical cord to the allantoic sac where it is stored
identify the structures of fetal circulation in the calf
identify the structures of fetal and postnatal circulation
branching of aorta in dog
canine arteries of the thorax
vessels on the floor of the thorax
equine structures within mediastinum
thoracic cavity of the dog
right lateral view of thorax
where does the vagus nerve arise from and run
arises from the vagosympathetic trunk to form part of the cardiac plexus
The left vagus continues over the base of the heart, gives rise to the left caudal recurrent laryngeal nerve (which curves around the aortic arch before ascending the neck) then splits into dorsal and ventral branches which follow the oesophagus towards the oesophageal hiatus.
The left dorsal and ventral vagal branches subsequently unite with the right dorsal and ventral vagal branches to form a single dorsal and ventral branch which accompany the oesophagus through the oesophageal hiatus of the diaphragm.
right lateral view of thoracic cavity
left lateral view of thorax
right lateral thorax
