Anticoagulant rodenticide toxicity: PT and aPTT
3-year-old Labrador with epistaxis, subcutaneous haematomas and lethargy for 24 hours. Lives in a house with a garden and a storeroom.
| Parameter | Result | Reference |
|---|---|---|
| Prothrombin time (PT) | > 100 s | 6–9 |
| aPTT | 38 s | 10–16 |
| Platelets | 210,000/µL | 200,000–500,000 |
| Fibrinogen | 250 mg/dL | 150–400 |
What is the most likely diagnosis?
chevron_right Show answer and explanation
A. Disseminated intravascular coagulation (DIC)
DIC presents with thrombocytopenia, fibrinogen consumption and raised D-dimers, and there is always a severe underlying disease. Here platelets and fibrinogen are normal.
B. Haemophilia A
Haemophilia A (factor VIII deficiency, intrinsic pathway) prolongs only the aPTT, with a normal PT, and usually shows in young males.
C. Von Willebrand disease
It is a primary haemostasis defect: normal PT and aPTT (or a minimally altered aPTT), with a prolonged buccal mucosal bleeding time and mucosal haemorrhage.
D. Anticoagulant rodenticide toxicity
Correct. Vitamin K antagonists block factors II, VII, IX and X. PT prolongs first and most because factor VII has the shortest half-life. Treatment: oral vitamin K1 for 3–4 weeks or longer, and plasma if there is active bleeding.
lightbulb Key takeaway
If ingestion is recent (< 2–4 h), induce emesis. Without signs, measure PT at 48–72 h. After finishing vitamin K1, recheck PT 48–72 h later: second-generation rodenticides persist for weeks.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.