NAVLE Canine Medicine and Surgery 6

Question 1

A 7-year-old intact male Golden Retriever presents with a 3-week history of progressive tetraparesis, bilateral pelvic limb weakness, and marked muscle wasting. MRI reveals an intradural-extramedullary mass at T3. CSF analysis shows albuminocytologic dissociation. Histopathology of the mass is most consistent with which diagnosis?

Accepted Answer

Peripheral nerve sheath tumor

Answer

Peripheral nerve sheath tumors (PNSTs) are the most common intradural-extramedullary spinal tumors in dogs, particularly large breeds. They arise from Schwann cells or perineural fibroblasts, and CSF frequently shows albuminocytologic dissociation (elevated protein without significant pleocytosis) due to blood-brain barrier disruption adjacent to the mass. Meningiomas are more common in the intracranial compartment in dogs. Nephroblastomas are typically intramedullary and occur in young dogs (usually <3 years) at T10–L2. Astrocytomas are intramedullary.

Question 2

A 4-year-old female Labrador Retriever undergoes gastropexy during a routine splenectomy following splenic torsion. Three days post-operatively she develops melena, hematemesis, and a PCV drop from 38% to 22%. Endoscopy reveals multiple deep gastric ulcers along the greater curvature. Which mechanism BEST explains this complication?

Accepted Answer

Ischemia-reperfusion injury to the gastric mucosa from prior gastric hypoperfusion

Answer

Splenic torsion is commonly associated with concurrent gastric dilatation-volvulus (GDV) or significant gastric hypoperfusion. Ischemia-reperfusion injury to the gastric mucosa — occurring when blood flow is restored after a period of ischemia — generates reactive oxygen species that disrupt mucosal barrier integrity, leading to ulceration. The greater curvature is particularly vulnerable due to its vascular territory. While portal hypertension and NSAIDs can cause ulcers, ischemia-reperfusion injury is the most physiologically consistent explanation given the surgical context and ulcer distribution.

Question 3

A 9-year-old neutered male Cocker Spaniel is diagnosed with immune-mediated hemolytic anemia (IMHA). Despite 72 hours of prednisolone (2 mg/kg/day), azathioprine, and heparin therapy, his PCV continues to decline from 18% to 12%. He is now dyspneic and tachycardic. Crossmatch reveals no compatible donor. Which transfusion strategy is MOST appropriate?

Accepted Answer

Transfuse with incompatible packed red blood cells, accepting accelerated hemolysis as an acceptable risk

Answer

In life-threatening anemia (PCV <12–15% with cardiorespiratory compromise), transfusion is indicated even when crossmatch-incompatible, because the risk of death from anemia outweighs the risk of accelerated hemolytic transfusion reaction. The transfused cells may survive only hours, but this 'buy time' approach can stabilize the patient while immunosuppression takes effect. Exchange transfusion is not standard of care for IMHA in dogs. Increasing steroids alone or delaying transfusion in a hemodynamically compromised patient is dangerous. hIVIG may be used as an adjunct but takes time to work and does not address immediate oxygen-carrying capacity.

Question 4

A 6-year-old male intact Beagle presents with a 4-month history of recurrent urinary tract infections and intermittent hematuria. Ultrasound reveals a 2.8 cm hyperechoic mass in the prostatic urethra. Biopsy confirms transitional cell carcinoma (TCC). Thoracic radiographs are clear. Which statement regarding treatment and prognosis is MOST accurate?

Accepted Answer

COX-2 inhibitor therapy is indicated regardless of other treatment modality due to documented partial response rates

Answer

Canine TCC (now termed urothelial carcinoma) overexpresses COX-2, and piroxicam (a non-selective COX inhibitor) has documented partial response rates (~17%) and stable disease rates (~57%), making it a cornerstone of TCC management regardless of whether chemotherapy is added. Piroxicam plus mitoxantrone has shown improved response rates over piroxicam alone in studies (not equivalent). Surgical resection is rarely curative due to urethral/trigone involvement and high local recurrence. Urethral stenting is actually used palliatively for urethral obstruction in TCC dogs, with tumor seeding along stent tracts not a documented clinical contraindication.

Question 5

A 5-year-old spayed female Border Collie presents with a 6-week history of progressive right forelimb lameness. Radiographs show a permeative lytic lesion at the distal radius with cortical destruction and a Codman's triangle. Fine-needle aspirate cytology reveals large polygonal cells with marked anisokaryosis. You initiate staging workup. Which finding would MOST significantly worsen the prognosis compared to the baseline expected survival with standard of care?

Accepted Answer

Regional axillary lymph node enlargement confirmed as metastatic on aspirate

Answer

Regional lymph node metastasis (confirmed histologically or cytologically) is a well-established negative prognostic indicator in canine appendicular osteosarcoma and upstages the disease. It is associated with significantly shortened survival times compared to dogs without nodal metastasis, even with amputation and chemotherapy. Elevated ALP is a negative prognostic factor but is common and does not change staging definitively. Pulmonary nodules detected only on CT but not radiographs are of uncertain significance and may be inflammatory. Skip metastasis to the scapula (detected by scintigraphy) suggests polyostotic disease, which is poor, but confirmed nodal spread is the most clearly documented survival-shortening finding listed.

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE Canine Medicine and Surgery 6