What is the top differential diagnosis for Rosie based on the case?

• A. Rodenticide toxicosis
• B. Rat poison infection
• C. Bloat
• D. Heartworm disease

Answer: (A)

Rodenticide toxicosis is the best fit when a patient presents with signs of bleeding or bruising after potential exposure to a toxin. Anticoagulant rodenticides block the vitamin K cycle, depleting vitamin K–dependent clotting factors II, VII, IX, and X. That causes a coagulopathy, leading to spontaneous or easy-to-bleed mucous membranes, petechiae, or internal hemorrhage. The earliest lab clue is a prolonged prothrombin time, since factor VII has the shortest half-life, with possible subsequent prolongation of other clotting times. If Rosie has a history or suspicion of ingesting rat poison and shows bleeding tendencies, rodenticide toxicosis becomes the leading consideration.

Diagnosis combines history and coagulation testing (PT preferred, with aPTT as needed). Treatment focuses on stopping exposure, giving vitamin K1 to restore the vitamin K–dependent factors (with duration tailored to the specific rodenticide, often weeks), and providing blood products if there is active bleeding or severely prolonged clotting times. Monitor PT to guide therapy length. The other options don’t align with a bleeding/coagulopathy presentation: bloat involves abdominal distension and retching; heartworm disease typically shows coughing and exercise intolerance; and “rat poison infection” isn’t a standard diagnosis in this context.