Diagnostic imaging of the respiratory tract 1 Flashcards
Describe normal lung radiograph
majority of lung radiolucent. most radiodense structures are pulmonary arteries and veins, arteries and veins branch and taper in the periphery. the pulmonary veins are ventral to the principal bronchus on the lateral view and medial to it on the VD and DV views (veins are ventral, veins are central).
What should you consider if there are signs of a pneumothorax?
Other signs of trauma - rib fractures (count ALL ribs), ruptured diaphragm, urinary bladder visible?
What should you consider if there are signs of pleural fluid?
- Tracheal or lobar displacement to suggest a mass?
- Cranial displacement of abdominal viscera?
What should you consider if there are signs of possible cardiac enlargement?
Any signs of cardiac failure? (left sided - pulmonary oedema versus right sided - hepatomegaly and ascites)
What should you consider if there are signs of dialted oesophagus?
signs of aspiration pneumonia
What should you consider if there are signs of ventral lung consolidation?
Look for oesophageal dilatation
What should you consider if there are signs of minimal pulmonary lesions in coughing animal?
look carefully for laryngeal and tracheal lesions
What should you consider if there are signs of an unexpected or puzzling lesion?
examine entire film again
Probable origin - cough that is exercise-induced - 3
larynx, trachea, cardiac disease
Probable origin - cough that is low-grade and persistent
bronchi, pulmonary lesion impinging on bronchi
Probable origin - noisy dyspnoea
Upper airway obstruction (laryngeal mass, tracheal stenosis, mass impinging on trachea)
Probable origin - quiet dyspnoea
SOL in thorax (pneumothorax, pleural fluid, mass, ruptured diaphragm)
Probable origin - cyanosis
Airway obstruction OR right-to-left shunt (ToF)
Probable origin - panting
Probably normal. Possibly cushings.
List the 5 different patterns visible when radiographing the nasal cavities.
- ) Normal
- ) Areas of increased soft tissue opacity superimposed over normal conchal pattern
- ) Areas of increased soft tissue opacity superimposed over areas of conchal destruction
- ) Areas of decreased opacity due to conchal destruction
- ) Mixed pattern
Possible cause - normal nasal passage appearance on radiography
Normal animal OR acute rhinitis
Possible cause - areas of increased soft tissue opacity superimposed over normal conchal pattern - 2
Chronic rhinitis
Nasal FBs
Possible cause - areas of increased soft tissue opacity superimposed over areas of conchal destruction - 2
Conchal destruction indicates aggressiveness - one of two options - aspergillosis (areas of increased and decreased opacity within the same side of the nose)OR neoplasia (more uniform destruction across nose, e.g. adenocarcinoma)
Possible causes - decreased opacity areas due to conchal destruction - 2
Aspergellosis OR neoplasia
Possible causes - mixed pattern (of increased and decreased opacity)
Aspergellosis OR neoplasia
What are the 3 broad manifestations of lesions affecting the upper airway?
- Occupy the airway
- Cause narrowing
- Cause narrowing and displacement
What might occupy the URT? 3
FB
Mucosal nodules due to Oslerus osleri
Neoplasm
What might cause narrowing of the URT? 5
- Tracheal hypoplasia
- Collapsing trachea
- Thickened tracheal membrane (severe tracheitis)
- Submucosal haemorrhage (coumarin toxicity)
- Neoplasm
What might cause narrowing and displacement of the URT?
Retropharyngeal lymphadenopathy mediastinal mass
What age-related changes might be seen in the lung? 3
Pleural lines, mineralised bronchial walls and mild hazy lung appearance.
Why is the non-dependent lung more informative on radiography?
The non-dependent part of the lung is better aerated (so provides a better background).
Do lung changes reflect specific aetiologies?
No - the lung responds to various aetiological factors in very few ways. Furthermore changes seen change over time and indicate disease progression or regression.
List the 5 different lung patterns
bronchial, interstitial, alveolar and vascular
(this is the order of disease progression too, reverse this order for regression either with treatment or spontaneously).
Mixed = where there is alveolar and interstitial patterns identified together.
Define bronchiectasis
a clinical sign, not a disease in itself. all untreated lung diseases end like this. the bronchi diameter are enlarged (i.e. they don’t taper towards the periphery)
How can you distinguish an interstitial from an alveolar lung pattern?
Interstitial - blood vessels are present
Alveolar - blood vessels are absent
Define bronchial pattern
mineralisation of the bronchial walls with age. Also thickening of the bronchial walls and/or increased diameter of the bronchi.
Causes - bronchial pattern - 5
- Bronchial mineralisation (age)
- Allergic bronchitis
- Chronic bronchitis
- Peribronchial cuffing (oedema)
- Bronchopneumonia
Causes - interstitial pattern
- pneumonia
- oedema
- haemorrhage of any cause
- neoplasia
Define interstitium
elements of the lung that do not contain air - alveolar and interlobular septa, microscopic BVs.
How is interstitial pattern characterised?
Localised or diffuse
Nodular or unstructured (hazy)
What is the sensitivity of radiology for pulmonary metastasis?
65-90% - right and left lateral view of the thorax are required.
Differentials - pulmonary nodules
- metastatic neoplasia*
- haematomas
- granulomas
- fluid-filled bronchi
- abscesses
How are primary pulmonary masses different?
larger than nodules and may cause displacement of the mediastinal structures to the contralateral hemithorax.
Causes - diffuse unstructured/lazy interstitial pattern - 5
- under-exposed radiograph
- radiograph taken in expiration
- old dog
lymphoma - pneumonia (viral, fungal, parasitic, metabolic, inhalant, toxic, idiopathic)
- diseases in transition (oedema, bronchopneumonia)
Causes - locaslised unstructured/lazy interstitial pattern - 5
- Partial lung collapse
- haemorrhage/contusion
- pulmonary embolism
- bronchial FB
- diseases in transition (bronchofilaria, dirofilariasis, oedema)
Describe the appearance of alveolar pattern in the lung
Characterised by the lack of air in the alveoli of the lung. Uniform increased lung opacity with NO visible pulmonary vessels in the affected area.
Describe how quickly the alveolar pattern can change in distribution and severity.
FAST (hours) - fluid
LONGER (days/weeks) - cellular infiltrate (pneumonia)
What is an air bronchogram? What is it characteristic of?
air-filled bronchi (dark) being made visible by the opacification of surrounding alveoli (grey/white). It is almost always caused by a pathologic airspace/alveolar process, in which something other than air fills the alveoli. Air bronchograms will not be visible if the bronchi themselves are opacified (e.g. by fluid) and thus indicate patent proximal airways.
CHARACTERISTIC of alveolar pattern
Ddx - localised alveolar pattern - 7
- bronchopneumonia
- oedema
- haemorrhage
- neoplasia
- lung collapse/atelectasis
- dirofilariasis
- pulmonary infarct
Ddx - diffuse alveolar pattern - 4
- severe bronchopnemonia
- severe oedema
- near drowning
- smoke inhalation
Characteristics - vascular pattern and causes - 4
- enlarged arteries - pulmonary hypertension
- enlarged veins - congestion from mitral insufficiency
- enlarged arteries and veins - overcirculation
- small arteries and veins - hypovolaemia, ToF
How is vascular size compared?
On the lateral view, the vessels should not have a diameter larger than the width of the proximal third of the 4th rib. On the DV/VD views, the arteries and veins at the level they cross the 9th rib, should not have a diameter larger than the width of the 9th rib.
Do the left and right pleural spaces communicate?
Yes - in most dogs. It is not normally visible radiograpically
What increases the visibility of the pleural cavity?
thickening of the pleural membrane or increased volume of pleural fluid results in widening of pleural fissures which increases their visibilities. Radiography useful for diagnosing pneumothorax or pleural effusion.
Name 3 key signs of pneumothorax
- radiolucent space between the cardiac silhoeutte and the sternum on the lateral thoracic radiograph
- lack of pulmonary vessels in the periphery of the thorax
- increased lung opacity
What suggests tension pneumothorax (i.e. high pressure pneumothorax)? Action?
The combination of a large volume of pleural air, marked pulmonary collapse and flattened diaphragm suggests this. Immediate thoracocentesis indicated.
What are key radiographc signs of pleural fluid? 4
- generalised increased opacity in the thoracic cavity
- loss of clarity of the cardiac silhouette and diaphragmatic outline
- separation of lung lobes from thoracic wall
- widened pleural fissures
What are bullae?
Air filled sacs that may be detected radiographically. No need to treat but record.
What is pulmonary enterotopic bone formation?
AKA bronchial calcification. not clinically significant.
What is the mediastinum?
2 layers of mediastinal pleura, separates thorax into 2 pleural cavities. Containts the trachea, oesophagus, heart, aorta/major branches, thoracic duct, LNs and nerves.
What does the mediastinum communicate with? 2
CRANIALLY: fascial planes of the neck
CAUDALLY: retroperitoneal space.
What size should the mediastinum be? Exception?
On the DV/VD views, the cranial mediastinum should not normally exceed twice the width of the vertebral bodies. The excpetion to this is bulldogs as they have a fat mediastinum.
What are signs of mediastinal shift? 2
- displacement of one or more of the mediastinal organs (e.g. heart) DV/VD view
- displacement towards/away from the affected hemithorax depending on cause
Radiographic signs - pneumomediastinum - 2
- radiolucency in mediastinum with increased visibility of BVs, oesophagus and tracheal wall
- secondary: gas lucency into fascial planes of neck and thoracic wall and pneumoretroperitoneum
Radiographic sign - mediastinal widening
Name 2 broad causes.
cranial mediastinum more than twice the width of vertebral bodies due to accumulation of fat or fluid.
Causes - mediastinal masses - 6
- neoplasia
- abscesses
- granulomas
- cysts
- sternal lymphadenopathy
- oesophageal dilatation secondary to vascular ring anomaly
Radiograhic signs - mediastinal masses
- soft tissue opacity superimposed on mediastinal area
- displacement of adjacent structures (esp. trachea)
- thymus normally visible in young animals
Why is the abdominal diaphragm rarely seen?
‘silhouetting’ with the adjacent liver
What is the normal point of intersection of diaphragm and spice?
between T11 and T13 normally but can be between T9 and T11.
Is the caval hiatus in the right or left crus of the diaphragm?
Right crus
Causes - cranial diaphragmatic displacement
ABDOMINAL - obesity, ascites, abdominal pain/masses, organomegaly
THORACIC - expiration, pleural adhesions, lung lobe atelectasis, lung lobectomy, diaphragmatic paralysis
Causes - caudal diaphragmatic displacement - 7
- Tension pneumothorax
- pleural effusion
- intrathoracic masses
- severe dyspnoea
- emphysema
- feline bronchial asthma
- emaciation
Causes - loss of outline of thoracic diaphragm surface
bilateral pleural effusion diaphragmatic hernia acquired diaphragmatic rupture alveolar pattern of adjacent lung caudal mediastinal masses
Causes - change in diaphragmatic contour/shape
Thoracic masses adjacent to diaphragm, small diaphragmatic ruptures/ hernias, pleural reaction on the diaphragmatic surface, diaphragmatic neoplasia, hemiparalysis of the diaphragm, unilateral tension pneumothorax, hypertrophic muscular dystrophy in cats (scalloped appearance)
Ultrasound signs - pleural effusion
displacement of echogenic lung surface away from transducer
Ultrasound sign - pleural mass
may appear as pleural thickening or as regular or irregular masses/nodules. variable
Is pneumothorax best assessed with xrays or ultrasound?
xrays
When can pulmonary consolidation/collapse be identified with ultrasound?
if the consolidation/collapse is in the cranial part of the lung, may also assist in identifying the cause
When can a pulmonary mass be identified with ultrasound?
when it is located int eh lung periphery
Can ultrasound be used to ID diaphragmatic hernia?
Yes
What are the 2 types of lung hyperlucency?
Diffuse and focal
Causes - diffuse lung hyperlucency - 6
- overexposure
- weight loss
- hypovolaemia
- overinflantion
- air trapping
- emphysema
Causes - FOCAL lung hyperlucency - 6
- bulla
- lobar emphysema
- pulmonary embolism
How can calcified lung lesions be classified?
Focal/multifocal OR diffuse
Causes - focal/multifocal calcified lung lesions - 6
Bronchial calcification
PHBF (pulmonary heterotopic bone formation)
Granuloma
Osteosarcoma mets
Primary lung neoplasm
Aspirated barium sulphate (contrast study)
Causes - diffuse calclified lung lesions - 4
- HAC
- HPTH
- Chronic uraemia
- Idiopathic
Define pneumothorax
Radiolucent space between cardiac silhouetter and sternum on the LATERAL thoracic radiographic. Lack of pulmonary vessels in the thorax periphery. Increased lung opacity.
What should you determine from a DV/VD radiograph of pneumothorax?
Is it unilateral or bilateral?
Causes - mediastinal shift
Unilateral pneumothorax/pleural effusion Diaphragmatic hernia Collapsed lung lobe(s) Chronic pleural diseases with adhesion Sternal and vertebtral abnormalities
Oblique projection may give the impression of mediastinal shift*
Causes of widened mediastinum - 7
- Obesity
- Thymic sail
- Haemorrhage
- Mediastinitis/abscess
- Oedema
- Chylomediastinum
- Mediastinal masses
How do air and fluid affect ultrasound for the respiratory tract?
Air is bad for ultrasound
Fluid increases detail in ultrasound.
What do you always think if you can’t see cranial diaphragm?
diaphragmatic hernia
Causes - diaphragmatic hernia - 4
- Enlarged cardiac silhouette with peritoneal pericardial diaphragmatic hernia (PPDH)
- Caudal mediastinal mass - P mediastinal diaphragmatic hernia (PMDH)
- Extrapleural mass
- Cranial/displacement/malposition of abdominal viscera
Pleural effusion?
Why are forelimbs pulled forward to take a lateral radiograph?
so that most of the tricpes musculature is not superimposed on the cranial aspect of thorax
Where is the xray beam centred for the VD view?
at level of 5th ICS (same as for the DV view)
Where is the xray beam centred for the lateral view?
caudal border of the scapula
Why is the lung normally radiolucent?
majority of lung is composed of air-filled structures - airways and alveoli
Where are pulnonary veins located on a normal radiography?
LATERAL VIEW: ventral to the principal bronchus
DV/VD VIEW: medial to the principal broncus
List some age-related changes of lung - 3
pleural lines
mineralised bronchial walls
mild hazy lung appearance
In what way can a normal diaphragm appear like on a VD view?
Mickey mouse appearance
In what way can a normal diaphragm appear like on a DV view?
British Policeman’s hat
