6 – Thoracic Radiography 2 Flashcards
Mediastinum
- Space b/w right and left pleural sacs
- Bounded on each side by mediastinal parietal pleura
- From thoracic inlet to the diaphragm
- Contains all thoracic structure BUT the lungs
Cranial mediastinum: what can you see?
- Cranial aorta
- Multiple important vasculature
- Some lymph nodes
- Soft tissue band: cranioventral mediastinal reflection (multiple pleura that surround the lung lobes)
- At front: L cranial slightly extends to right side
Middle mediastinum: what can you see?
- Caudal portion of thoracic trachea
- Cardiac silhouette
- Lymph nodes (tracheal-bronchial)
Caudal mediastinum: what can you see?
- Not many structures
- Descending aorta
- Caudal vena cava
- Caudal mediastinal reflection (can only see in DV/VD view)
o Accessory lung lobe pushes It to the left side
o Multiple pleura’s=normal structure
What is one of the most common mediastinal disease?
- Mediastinal lymphoma
o Displaces many structures (ex. trachea displaced)
Trachea in normal conditions
- Lumen is radiolucent (filled with air)
- Sligh angle relative to axis of thoracic spine rather than parallel (lateral views)
- May be slightly to the right of thoracic spine on VD/DV views
What are some normal variations that might happen with the trachea?
- Dorsal displacement secondary to changes in head positioning
- Redundant dorsal tracheal membrane
Redundant dorsal tracheal membrane
- Broad based soft-tissue opacity protruding from the dorsal tracheal walls
- Can be incidental OR may be associated with collapsing airway
o Present in large breed dogs
Collapsing trachea
- Disease process, toy/small breeds
- Airway collapse
- ENTIRE lumen being narrowed (not just the walls)
- Honking cough and respiratory distress
Normal esophagus
- NOT visible
Generalized esophageal dilation
- May occur due to hypomotility secondary to sedation/GA OR disease processes
- Congenital megaesophagus
- Acquired megaesophagus
o Hypothyroidism
o Myasthenia gravis
o Paraneoplastic (thymoma)
o Dysautonomia
o Polyneuropathy
o Toxicity
- Acquired megaesophagus
Esophagram: dogs and cats
- Use static barium esophagram
o *Contraindicated for esophageal perforation! - Dogs: linear mucosal folds
- Cats: ‘herringbone’ appearance of mucosa at caudal esophagus due to obliquely oriented smooth muscle
What are the clinical relevant lymph nodes located in the mediastinum?
- Sternal lymph nodes=usually the only one that can be visualized (R. lateral)
- Cranial mediastinal lymph nodes
- Tracheobronchial lymph nodes
Sternal lymph node
- Only one that is visualized in right lateral view above the 2nd or 3rd sternebrae
- DRAINS the CRANIAL ABDOMEN, ribs, sternum, thymus, adjacent muscles and mammary glands
Cranial mediastinal lymph nodes
- Lie just ventral to trachea
- Superimposed by the vasculatures
Three tracheobronchial lymph nodes
- Right and left lie abaxial to the carina
- Middle is just caudal to tracheal bifurcation
Diaphragm
- Left crus
- Right crus
- Cupula
Pleural space in normal conditions
- Not visualized
- Occasionally, solitary interpleural fissure ID due to tangential X-ray beam or pleural thickening
Pleural space: abnormal conditions
- Multiple and easily identifiable interpleural fissures
- Fluid or air filling the pleural space
Thoracic walls
- In some dogs as cats (older), costochondral degeneration
o Osseous proliferation may be present=incidental
o Do NOT confuse with lung nodules or with aggressive bone lesions (infection or neoplasia)
Thymus
- Young animals (<4months)
- “looks like a ‘sail’
- Cranioventral mediastinal reflection
Cranial mediastinal fat deposition
- Obese dogs
- Opacity is in between the lungs and cardiac silhouette opacity=fat
Why might you use non-standard radiographic views?
- Aid in diagnosis of small volume of pleural effusion or pneumothorax
- Reduce effacement of a thoracic mass by pleural effusion
- Complex diaphragmatic hernias
- Unstable patients (ex. respiratory distress): standing patient
Left lateral recumbency horizontal view
- Detection of small volume of pleural effusion
Standard orthogonal views: see a soft-tissue opacity in right ventral hemithorax
- Differentials
o Pleural effusion
o Diaphragmatic hernia - *use dorsal recumbency horizontal beam
Dorsal recumbency horizontal beam: when see a soft-tissue opacity in right ventral hemithorax
- Detection of diaphragmatic hernia
- If there was pleural effusion: it would accumulate in dorsal thoracic region (gravity dependent aspect) rather than ventral
Equine thorax
- Patient standing: horizontal X-ray beam
- Equipment
o Large, stationary x-ray tube
o High output
o Large plate
o Portable in foals
What are the 4 quadrants for equine thoracic radiographs?
- Craniodorsal
a. Heart, aorta, main bronchi, caudal vena cava, diaphragm - Caudodorsal
- Caudoventral
a. Heart, aorta, main bronchi, caudal vena cava, diaphragm, carina - Cranioventral
a. Trachea, hear, lungs and cranial mediastinum
Thoracic ultrasound
- Abnormal ‘wet’ lung: B-lines
o DDx: pulmonary edema OR pneumonia - Lung consolidation: “shred sign”
- Lung nodule
- Intra-thoracic mass
- Pleural effusion
