DVM Clinical Pathology and Diagnostics 3 — Questions and Answers
Question 1: A cat has a platelet count of 28,000/µL with large platelets on smear and no evidence of bleeding. What should be ruled out first?
- Immune-mediated thrombocytopenia
- Platelet clumping artifact (Correct answer)
- Bone marrow failure
- DIC
Correct answer: Platelet clumping artifact
Feline platelets commonly clump in EDTA samples, causing a falsely low count; smear evaluation for clumps is essential before diagnosing true thrombocytopenia.
Question 2: Which urine sediment finding is pathognomonic for ethylene glycol toxicity in dogs?
- Struvite crystals
- Calcium oxalate monohydrate crystals (Correct answer)
- Cystine crystals
- Ammonium biurate crystals
Correct answer: Calcium oxalate monohydrate crystals
Calcium oxalate monohydrate (hippurate) crystals in urine sediment are characteristic of ethylene glycol metabolism and are highly diagnostic.
Question 3: A dog has an ALT of 850 IU/L and AST of 420 IU/L with normal ALP. Which organ is most likely the primary source?
- Pancreas
- Kidney
- Liver (Correct answer)
- Skeletal muscle
Correct answer: Liver
ALT is highly liver-specific in dogs, and marked elevation with concurrent AST rise points to hepatocellular injury as the primary source.
Question 4: A horse has peritoneal fluid with a total protein of 3.8 g/dL and nucleated cell count of 12,000/µL with 90% neutrophils. What is the diagnosis?
- Normal peritoneal fluid
- Transudative effusion
- Septic peritonitis (Correct answer)
- Chylous effusion
Correct answer: Septic peritonitis
Elevated protein and a predominantly neutrophilic pleocytosis above 10,000/µL in equine peritoneal fluid indicates septic peritonitis.
Question 5: On a blood smear from a febrile dog returning from the southeastern US, you observe morulae within neutrophils. Which organism is implicated?
- Anaplasma phagocytophilum (Correct answer)
- Ehrlichia canis
- Babesia canis
- Hepatozoon americanum
Correct answer: Anaplasma phagocytophilum
Anaplasma phagocytophilum infects neutrophils and forms characteristic morulae (intracytoplasmic inclusion bodies) within these cells.
Question 6: A dog with suspected Addison's disease has a sodium:potassium ratio of 19:1. What is the significance of this finding?
- Normal; no further workup needed
- Suggests hyperaldosteronism
- Supports hypoadrenocorticism; ratio below 27:1 is suspicious (Correct answer)
- Indicates diabetes insipidus
Correct answer: Supports hypoadrenocorticism; ratio below 27:1 is suspicious
A Na:K ratio below 27:1 raises suspicion for hypoadrenocorticism due to aldosterone deficiency causing sodium loss and potassium retention.
Question 7: Which finding on synovial fluid analysis is most consistent with septic arthritis in a dog?
- Nucleated cell count of 2,000/µL with 60% mononuclear cells
- Nucleated cell count >40,000/µL with >90% neutrophils and intracellular bacteria (Correct answer)
- Pink-tinged fluid with increased RBCs
- Highly viscous fluid with low cell count
Correct answer: Nucleated cell count >40,000/µL with >90% neutrophils and intracellular bacteria
Septic arthritis is characterized by markedly elevated nucleated cell counts (>40,000/µL), predominantly degenerate neutrophils, and intracellular bacteria on cytology.
DVM Clinical Pathology and Diagnostics 3
A cat has a platelet count of 28,000/µL with large platelets on smear and no evidence of bleeding.
What should be ruled out first?