This week there were some great cross-sectional imaging cases. One of the main points was to apply the same principles of interpretation to CT and MR images, regardless of which one you are more used to seeing at your practice for a particular lesion.
9 year old female neutered German Shepherd with polyuria/polydipsia.
On post-contrast CT images, there is a large, contrast-enhancing mass involving the pituitary. The mass is slightly asymmetric with a non-contrast enhancing region on the dorsolateral right side. The primary differential diagnosis is pituitary adenoma or adenocarcinoma. Differentials that could mimic a pituitary tumor include meningioma, granular cell tumor, and lymphoma (tends to be more diffuse). Diagnosis: Pituitary mass. Note: In human literature, pituitary adenocarcinomas are only diagnosed if there is intracranial metastatic disease. Non-metastatic tumors are termed adenoma or invasive adenoma.
12 year old Boxer with vestibular signs.
Post-contrast CT images of the brain are available. There is atrophy of the temporalis muscle and digastricus muscle on the right side. There is a broad-based, contrast-enhancing area on the left side of the brain adjacent to the tympanic bulla. It is in the region of the vestibulocochlear nerve and appears to be extra-axial with a dural tail. The tympanic bulla is normal, however mineralization of the external ear canal indicates chronic otitis externa. The primary differential diagnosis is meningioma; less likely differentials include lymphoma, peripheral nerve sheath tumor, and inflammatory disease. Diagnosis: Meningioma.
3 year old QH gelding with grade 4/5 right front lameness after trauma.
On ultrasound images, the superficial digital flexor tendon is enlarged from 19-23 cm distal to the ACB. There is a hypoechoic region with irregular fiber pattern at the caudal margin which becomes normal at 27 cm distal to the ACB. There is also moderate digital sheath effusion. There is hypoechoic relaxation artifact in the inferior check ligament which may indicate rupture of the check ligament or the deep digital flexor tendon. Differential diagnoses – superficial digital flexor tendon desmitis and check ligament rupture or rupture of the deep digital flexor tendon with secondary check ligament relaxation. Recommendation: scan the pastern to evaluate the deep digital flexor. There is a large anechoic, irregular region in the deep digital flexor tendon at the level of the pastern with severe fiber disruption. The margins of the deep digital flexor is difficult to define. Diagnosis: Superficial digital flexor tendon desmitis and deep digital flexor tendon rupture.
2 year old gelding with a mass on left mandible.
CT images of the skull are available. There is an expansile mass with irregular internal mineralization associated with the right caudal mandible. There is no evidence of cortical lysis. The mass surrounds M3 and is cauding abnormal shape and eruption of M3. M2 is also surrounded by the mass but has a normal shape. The oral cavity is narrowed by the mass. The main differential diagnosis is a congenital mass of dental origin such as ameloblastoma or cementoma, odontoma, or benign tumor such as fibroma. Note: ameloblastomas are radiolucent. Diagnosis: complex ameloblastic odontoma.
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