NAVLE Diagnostic Imaging Interpretation 5 — Questions and Answers
Question 1: On a lateral thoracic radiograph of a dog, which structure should be used to assess left atrial enlargement?
- Dorsal elevation of the left mainstem bronchus (Correct answer)
- Increased sternal contact of the cardiac silhouette
- Displacement of the trachea ventrally at the carina
- Widening of the right cardiac border
Correct answer: Dorsal elevation of the left mainstem bronchus
Left atrial enlargement causes dorsal elevation and splaying of the left mainstem bronchus (carina angle >60°) on lateral radiographs.
Question 2: Which ultrasonographic finding is MOST consistent with gastric dilatation-volvulus (GDV) versus simple dilatation in a dog?
- Compartmentalization of the stomach into two gas-filled regions on the right lateral view (Correct answer)
- Uniform gastric distension with fluid content
- Inability to obtain gastric images due to gas artifact
- Thickening of the gastric wall with loss of wall layering
Correct answer: Compartmentalization of the stomach into two gas-filled regions on the right lateral view
GDV causes the stomach to rotate, creating a compartmentalized 'double bubble' appearance, whereas simple dilatation shows uniform distension.
Question 3: Acoustic shadowing on ultrasound is caused by:
- Complete absorption or reflection of the sound beam by a highly attenuating structure (Correct answer)
- Bending of the ultrasound beam at curved interfaces
- Amplification of returning echoes beyond the gain setting
- Refraction of sound through soft tissue-fluid interfaces
Correct answer: Complete absorption or reflection of the sound beam by a highly attenuating structure
Dense structures such as calculi or bone absorb or reflect nearly all the ultrasound energy, preventing transmission and creating a shadow distal to the structure.
Question 4: In equine foot radiography, which landmark is used to assess the position of the navicular bone relative to the distal phalanx?
- Palmar angle of the distal phalanx relative to the ground surface (Correct answer)
- Dorsal cortex width of the middle phalanx
- Solar margin of the coffin bone on dorsopalmar view
- Angle of the coronary band to the hoof wall
Correct answer: Palmar angle of the distal phalanx relative to the ground surface
The palmar angle of P3 on lateral foot radiographs is used to assess navicular bone position and the degree of podotrochlear pathology.
Question 5: On CT myelography of a dog, an 'intramedullary' lesion is characterized by:
- Fusiform swelling of the spinal cord with thinning of the contrast column on all sides (Correct answer)
- Extradural deviation of the contrast column to one side only
- Complete block of contrast flow with a concave meniscus
- Widening of the subarachnoid space without cord deformation
Correct answer: Fusiform swelling of the spinal cord with thinning of the contrast column on all sides
Intramedullary lesions expand the cord itself, producing symmetric fusiform cord enlargement that thins the contrast column circumferentially.
Question 6: Which finding on plain thoracic radiographs is MOST suggestive of a cranial mediastinal mass in a cat?
- Loss of the cranial cardiac border and elevation of the trachea (Correct answer)
- Perihilar alveolar pattern
- Caudal mediastinal widening
- Pleural fissure lines
Correct answer: Loss of the cranial cardiac border and elevation of the trachea
Cranial mediastinal masses obscure the cranial cardiac silhouette and displace the trachea dorsally or laterally, a common presentation in cats with lymphoma.
Question 7: On abdominal radiographs, which finding is MOST consistent with uroabdomen (uroperitoneum) in a dog?
- Loss of serosal detail with retrograde urethrogram showing contrast extravasation (Correct answer)
- Increased opacity of the retroperitoneal space only
- Mineralized density within the bladder lumen
- Dilation of the ureters on excretory urogram
Correct answer: Loss of serosal detail with retrograde urethrogram showing contrast extravasation
Uroabdomen presents as loss of intraperitoneal serosal detail (due to urine effusion); a retrograde urethrogram or cystogram confirms contrast extravasation at the rupture site.
NAVLE Diagnostic Imaging Interpretation 5
On a lateral thoracic radiograph of a dog, which structure should be used to assess left atrial enlargement?