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Thoracic Imaging

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sihirlifil's version from 2017-09-26 15:16

Thorax General

Question Answer
Radiographic technique for thoraxFast film screen combination
Short time & high mA (=high mAs)
Sedation!
Radiographic views:DV
Lateral recumbency
Standing lateral (use horizontal beam) (radiation safety issues)
First view you take should be? Why?DV! Avoids artefactual decrease of lung volume from prolonged lateral recumbency
T/F Expiratory studies are best to show thoracic detailF! Lungs need to be aerated for better contrast with soft tissue opacities
Right lateral recumbency: crura of diaphragm look like?Parallel (CVC disappers)
Left lateral recumbency: crura of diaphragm look like?Y-shape
What happens to the cardiac silhouette on VD view?Apex flops backwards, so appears longer
What normal thing can be mistaken for pneumothorax on VD?Skin folds
How does a cat cardiac silhouette look different from a dog w/ lateral view?45 degree angle to sternum
What is this? Area of normal costodiaphragmatic recess in cats
Lung tip peels away from spine (sign of pleural effusion in dog)
Positional radiograpy used for?Move pleural fluid away from area of interest
Maximize lung inflation to look for small lesions
Only for stable patients!
Normal mediastinum should lookLies within width of vertebral column (fat dogs: wider. Greyhound: thinner)
What happened here? LLR view was taken first, animal was recumbent for 20 minutes. So recumbent (left) lung was compressed, didn’t have time to reinflate
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Pleural Cavity

Question Answer
Pleural cavity =? Can we usually see it?Potential space. Not usually ID unless it contains fluid, air, mass
What are the lines indicating? Normal pleural fissure locations
Pleural fluid: radiographic signs?Lungs retract from ribs
Fluid opacity surrounds lung lobes
Scalloping of lung edges
Pleural fissures visible (fluid dissects individual lobes out)
Dorsal displacement of the trachea
(Dogs: fluid in diaphragmatico-lumbar recess)
Pleural fluid
With only small volumes of pleural fluid, you can still see…Rounding of costo-diaphragmatic recess (1st place to ID fluid)
Fluid between accessory & left caudal lung lobe
Diagnostics for pleural fluid?Ultrasound- examine pleural cavity while fluid present
Thoracocentisis (cytology, bact/fungal culture)
Thoracostomy drain if vluid volume not reduced sufficiently
Pyothorax: more common in?Cats
Pyothorax looks like?Unilateral pleural fluid
Chylothorax may result from?Systemic disorders (caridac, hepatic)
Fibrosis can be seen when?Older dogs develop fibrin tags over time
Sequela to pleural infection, hemorrhage
Pneumothorax =Accumulation of air in pleural space with secondary collapse of lung lobes
Types of pneumothoraxUnilateral
Bilateral
Tension
Pneumothorax: radiographic signs?Lung lobes retract from ribs
Air opacity surrounds lung edges
Looks like overexposure
Cardiac shadow separated from sternum
Mediatstinal shift
Pneumothorax (collapsed lung lobe edges, cardiac shadow displaced from sternum)
What is a tension pneumothorax?Air enters pleural cavity but is unable to escape
Radiographic signs of tension pneumothorax?Caudal displacement of diaphragm (if bilateral)
Tenting of costo-diaphragmatic margins, muscular insertions become reversed
SEVERE retraction of lungs from ribs, spreading of ribs
Excess gas in GI tract
Tension pneumothorax
Pneumomediastinum can result from?Trauma to thorax or neck, tracheal/esophageal rupture, alveolar damage, paraquat poisoning
Pneumomediastinum: where’s all the air going?Tracks along pervascular sheath
Mediastinal free air (outlines brachiocephalic trunk, CVC)
Migrates from mediastinum into cervical & thoracic soft tissue
Migrates along aorta into retroperitoneum (makes aorta more visible)
Pneumomediastinum (severe subq emphysema)
Cranial mediastinal mass ddxThymic/esophageal abnormality, lymphadenopathy, neoplasia, infection
Middle mediastinal mass ddxPerihilar lymphadenopathy, heart base tumors, esophageal neoplasia
Caudal mediastinal mass ddxEsophageal abnormality, abscess, granuloma, neoplasia
Mediastinal mass: radiographic signs?Tracheal elevation (can be also deviated L/R/D/V depending on cause)
Obscured cranial cardiac shadow
Mediastinal mass (tracheal elevation, obscured cardiac silhouette)
If on US you see a ST opacity (hyperechoic) that’s homogenous, what are you thinking?It’s probably fluid, not a cyst (need centesis/FNA for cytology)
Hilar lymphadenopathy: radiographic signs?Increased opacity
Displacement/splitting of mainstem bronchi
Trachea can be displaced ventrally, esophagus dorsally
Hilar lymphadenopathy (Trachea makes right-angle bend, LN ventral & caudodorsal)
Normal mediastinum should be how big?No more than 2x the width of the vertebral column
Widened mediastinum could mean…Blood
Blood in mediastinum: VD looks like?Fluid outlines fissures in reverse direction (Christmas tree pattern)
Blood in mediastinum: DV looks like?Fluid pools in sternum, cardiac shadow poorly defined, mediastium looks wide
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Trachea & Hernia

Question Answer
Possible pathologies relating to the trachea?Tracheal collapse
Perforation
Foreign body (usually end up in lungs)
Filaroides Osleri parasite (form nodules, plques in lumen)
Tracheal stricture (compression, avulsion)
Tracheal neoplasia (condrosarcoma)
Ventral displacement of the trachea can indicate? Dorsal?Ventral: dilated esophagus
Dorsal: Enlarged cardiac silhouette, mediastinal mass
Where does the trachea usually bifurcate?At 5th thoracic vertebra over the heart base (origin of R cranial bronchus seen end-on)
Tracheal collapse: ___ trachea collapses in expiration, ___ trachea collapses in inspirationIntrathoracic during expiration
Extrathoracic during inspiration
Signs of tracheal collapse:Narrowing of tracheal lumen NOT due to normal narrowing at thoracic inlet or head hyperextension/flexion
A dog with tracheal collapse presents how?Goose-honk, open mouth breathing
What is helpful to treat tracheal collapse?Stents
Tracheal collapse usually diagnosed byFluoroscopy
Often have to take inspiratory AND expiratory lateral radiographs
Tracheal collapse
Common causes of tracheal perforationTrauma (HBC/RTA)
Stick injuries
Bites
Tracheal perforation: radiographic signs?Subcutaneous air
Interruption of tracheal rings (disrupt symmetry)
Narrowing of tracheal lumen
Tracheal stricture following perforation (inflammation, soft tissue mass both sides of trachea)
Tracheal foreign body (at bifurcation)
Tracheal hypoplasia common signalmentBrachycephalic (Bulldog)
How does tracheal hypoplasia present?Exercise intolerance, persistant infections
Tracheal hypoplasia: What is the diameter like?Less than 1/2 that of larynx or less than the width of proximal 3rd of the 3rd rib
Tracheal hypoplasia: radiographic signs?Grossly narrowed lumen throughout length
Tracheal hypoplasia
Before anesthesia, if you don’t measure the ET tube length correctly, what can happen?Bronchial intubation
How does bronchial intubation (anesthesia) look on radiographs?VD: Intubated side is obstructed, no longer aerated
Lateral: CAN LOOK NORMAL!
What’s going on here?
ET tube is malpositioned, so less of anesthetic gas is getting down to the lungs (patient probably not staying under too well)
What can happen with a non-reinforced ET tube?Kinks when neck is flexed
Diaphragmatic hernia: radiographic signs?Trachea elevated
Cardiac shadow obscured & elevated, can also be displpaced L/R
+/- intestinal contents in thorax
Diaphragm looks abnormal in abdomen
Diaphragmatic hernia: how do CS develop?Diaphragm contracts around small piece of liver/intestine/etc that comes through, the piece in the chest becomes congested, leaks fluid through here. Gradually patient develops dyspnea, fluid builds up, CS get worse & worse
If there’s pleural fluid and you suspect a hernia, how do you radiograph?Post thoracic drainage (get rid of the fluid hen re-radiograph to see abnormal ST opacities better)
If the stomach herniates into the thorax…EMERGENCY! It inflates, compromises the lungs and compresses CVC
Perioneo-pericardial hernia: happens in who? Is it serious?Cats. Congenital abnormality (incomplete separation of thorax & abdoment during fetal development)
Often incidental finding
Perioneo-pericardial hernia (intestines in pericardial sac)
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Ribs & Sternum

Question Answer
Rib neoplasia: what types? Common?Uncommon
Chondrosarcoma, sometimes osteosarcoma or fibrosarcoma
What is the “iceberg effect?”Minimal mass externally, but large expansile mass internally
Owner notices little lump, but tumor is much bigger in chest cavity
Rib neoplasia: radiographic signs?Displaced pleura and lung
Curved convex extrapleural sign
(Rib expansion, periosteal proliferation, bone proliferation/lysis)

(what are short arrows pointing to? Long?)
Rib neoplasia (short arrow = extrapleural sign. Long = erosion, lysis of rib)
Possible pathologies relating to the ribs?Fractures (simple/multiple)
Subcutaneous air (when skin lacerated)
Soft tissue swelling
Pneumothorax (pulmonary contusion)
Pleural fluid
Mediastinal shift (away from site of fracture)
What happens with flail chest?Fractured segment has paradoxical movement- fracture segment moves inward during inspiration (opposite direction to other ribs)
Flail chest: what happens with the isolated part of ribs?Presses into lungs, causes massive subq emphysema (need to pull out of chest and wire into place)
Possible pathologies relating to the sternum?Congenital anomaly- Pectus excavatum
Fracture/dislocation
Sternal inversion secondary to tracheal avulsion
Pectus excavatum (sternum completely everted)
Feline asthma looks like?Patient is dyspneic with hyperinflated lungs, diaphragm pushes back (can go all the way to L2) and concave (not convex like normal
Flexible sternum gets pushed up
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