NAVLE Diagnostic Imaging Interpretation 6

Question 1

A 7-year-old intact male German Shepherd presents for progressive pelvic limb ataxia. Myelography reveals an extradural compressive lesion at L7-S1 with a 'golf tee' sign on the lateral view. CT confirms a lateralized, calcified mass with a 'popcorn' mineralization pattern within the intervertebral foramen. Which diagnosis is most consistent with this imaging constellation?

Accepted Answer

Hansen Type I intervertebral disc extrusion with foraminal migration

Answer

Hansen Type I disc extrusion can migrate laterally into the intervertebral foramen, producing the classic 'golf tee' extradural sign on myelography. Calcified disc material from Type I (chondroid metaplasia) produces the 'popcorn' mineralization pattern on CT. Nerve sheath tumors are typically non-mineralized and cause foraminal widening/erosion. Synovial cysts are periarticular soft-tissue densities without calcification in this pattern. Degenerative lumbosacral stenosis shows diffuse stenosis rather than a discrete foraminal mass.

Question 2

On a thoracic radiograph of a 10-year-old DSH cat, you identify a soft-tissue opacity in the caudodorsal lung field that effaces the descending aorta but preserves the diaphragmatic silhouette. The lesion has a sharp ventral border and an indistinct dorsal border. Which anatomic compartment and silhouette sign interpretation is correct?

Accepted Answer

Caudodorsal pulmonary mass in the caudal lung lobe; positive silhouette sign with the aorta indicates the lesion is in contact with the aorta or the periaortic space

Answer

A positive silhouette sign occurs when two structures of the same opacity (soft tissue) are in contact, causing their borders to be indistinguishable. Loss of the aortic silhouette indicates the caudodorsal lung lesion is in anatomic contact with the aorta or periaortic mediastinum — this localizes the mass to the caudal lobe or posterior mediastinum. The preserved diaphragmatic line rules out diaphragmatic hernia. Pleural effusion would cause a diffuse gravity-dependent opacity, not a discrete mass with a sharp ventral border. This pattern is classic for a primary lung tumor (e.g., adenocarcinoma) in the caudal lung lobe abutting the mediastinum.

Question 3

A 3-year-old Quarter Horse presents with right forelimb lameness localized to the foot by perineural anesthesia. MRI (low-field standing unit) shows a hyperintense T2 signal lesion within the lateral lobe of the deep digital flexor tendon (DDFT) at the level of the navicular bone, with a corresponding hypointense T1 signal. The navicular bone shows focal subchondral signal loss on T1 at the flexor cortex. Which combination of lesions is present?

Accepted Answer

DDFT core lesion (longitudinal split tear) with navicular bone flexor cortex erosion

Answer

Hyperintense T2 / hypointense T1 signal within the DDFT substance indicates a fluid-filled cleft consistent with a longitudinal split tear (core lesion). This is distinct from surface fibrillation, which would show signal change only at the tendon margin without intrinsic disruption. The focal subchondral T1 hypointensity at the navicular flexor cortex indicates bone erosion or fibrocartilage loss — a recognized sequela of chronic DDFT pathology compressing the navicular bone. Navicular bursitis alone would show bursal distension with signal change in the bursal recess, not intrinsic tendon signal. Impar ligament desmitis produces signal change at the palmar distal navicular-P3 interface.

Question 4

Abdominal ultrasound in a 9-year-old spayed Labrador reveals a 3.2 cm splenic mass with a heterogeneous echotexture containing multiple anechoic cavities and a hyperechoic rim. Doppler interrogation shows no internal vascularity within the cavities. Fine-needle aspirate of the solid component yields blood only. Which imaging feature most strongly argues AGAINST a diagnosis of splenic hemangioma in favor of hemangiosarcoma?

Accepted Answer

Simultaneous detection of a hypoechoic hepatic nodule with similar internal architecture

Answer

Splenic hemangioma and hemangiosarcoma can appear nearly identical on ultrasound — both produce heterogeneous masses with blood-filled cavities, and non-diagnostic FNA is common in both. The single most distinguishing imaging feature suggesting malignancy (hemangiosarcoma) is multifocal involvement: a synchronous hepatic lesion with the same architecture strongly implies metastatic hemangiosarcoma, as the liver is the most common metastatic site. Anechoic cavities and absent Doppler flow within cavities are seen in both benign and malignant vascular tumors. The hyperechoic rim is a nonspecific finding seen with any expansile splenic mass causing parenchymal compression.

Question 5

A lateral skull radiograph of an 8-month-old Boxer shows a multilocular, expansile radiolucent lesion of the mandible with a 'soap bubble' internal architecture and cortical thinning without periosteal reaction. The lesion is centered on the mandibular premolar region. Which diagnosis is most consistent, and what additional imaging modality would best characterize the lesion before surgery?

Accepted Answer

Canine acanthomatous ameloblastoma; CT with bone algorithm for cortical integrity and tooth root involvement

Answer

Canine acanthomatous ameloblastoma (CAA, formerly adamantinoma) classically presents in young to middle-aged dogs — particularly Boxers — as an expansile, multilocular 'soap bubble' radiolucent mandibular lesion. Unlike osteosarcoma, CAA is locally invasive but rarely metastasizes; its hallmark is bone invasion without distant spread. CT with a bone algorithm is the standard pre-surgical modality because it precisely delineates cortical penetration, tooth root resorption, and the true extent of bone involvement — critical for planning marginal vs. segmental mandibulectomy. Dentigerous cysts are unilocular pericoronal lucencies, not multilocular. MLO (multilobular osteochondrosarcoma) typically affects the calvarium or hard palate with a 'popcorn' mineralized matrix, not a purely radiolucent jaw lesion.

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE Diagnostic Imaging Interpretation 6