RBC Rundown
What is the most immunogenic blood group in dogs?
DEA 1.1 — It’s the most antigenic canine blood type and must be avoided in transfusions.
Name the receptor that allows platelets to adhere to vWF.
GPIb receptor — binds vWF for platelet adhesion.
Which coagulation factor has the shortest half-life?
Factor VII
Which breed is the “poster child” for von Willebrand Disease, and what type of hemostatic defect is this?
Doberman Pinscher — Primary hemostatic defect due to vWF deficiency.
Define hemostasis in one sentence.
Process that halts bleeding via vascular constriction, platelet plug formation, and coagulation.
Which RBC shape change is typically seen with oxidative damage (e.g., onion or acetaminophen toxicity)?
Heinz bodies — Denatured hemoglobin caused by oxidative stress.
What are the top 3 differentials for a primary hemostatic defect?
Thrombocytopenia, vWF deficiency, abnormal platelet function.
List the four vitamin K-dependent coagulation factors.
Factors II, VII, IX, X (“1972”).
What type of hemostatic defect is most often seen in German Shepherds, and which factor is involved?
Hemophilia A — Secondary hemostatic defect involving Factor VIII (intrinsic pathway).
What are the three stages of hemostasis?
Primary (platelet plug), Secondary (coagulation cascade), Tertiary (fibrinolysis).
What type of anemia shows macrocytic hypochromic indices?
Regenerative anemia — Immature RBCs are larger with less hemoglobin.
A Doberman presents with mucosal bleeding but normal platelet count and prolonged BMBT. What disorder is most likely?
von Willebrand Disease (type I)
In which pathway is Factor XII located, and what activates it?
Intrinsic pathway; activated by contact with negatively charged collagen fibers.
Greyhounds are predisposed to delayed postoperative bleeding. What mechanism causes this?
Hyperfibrinolysis — excessive fibrin breakdown due to elevated plasmin activity (tertiary hemostasis).
Which test differentiates between primary vs secondary hemostatic disorders?
BMBT evaluates primary; PT/PTT evaluate secondary hemostasis.
Horses rarely show reticulocytosis. What morphologic sign best indicates regeneration?
Macrocytosis — Increased MCV is the best evidence of regeneration in horses.
List two mechanisms that can cause immune-mediated thrombocytopenia.
Secondary to drugs, rickettsial infection, or neoplasia (triggering antiplatelet antibodies).
How does warfarin cause bleeding disorders?
Warfarin blocks vitamin K epoxide reductase → inactive factors II, VII, IX, X.
What is the most likely cause of bleeding in a cow grazing on moldy sweet clover, and which vitamin is affected?
Vitamin K antagonism — secondary hemostasis defect from inhibited carboxylation of Factors II, VII, IX, X.
What condition affects both primary and secondary hemostasis simultaneously?
DIC — causes both platelet consumption and coagulation factor use.
Describe the key difference between extravascular and intravascular hemolysis.
Extravascular = macrophages remove damaged RBCs → icterus; Intravascular = RBCs lyse in vessels → hemoglobinemia/uria.
Explain why severe thrombocytopenia (< 20,000/µL) causes spontaneous hemorrhage.
Platelet numbers drop below threshold to form plugs, leading to capillary leak and mucosal bleeding.
Name one physiologic anticoagulant molecule and its target.
Antithrombin III — inhibits thrombin and factor Xa (heparin enhances it).
Explain how Disseminated Intravascular Coagulation (DIC) affects multiple stages of hemostasis.
DIC simultaneously activates coagulation (widespread clotting) and consumes platelets/coag factors, leading to both thrombosis and hemorrhage — affecting primary, secondary, and tertiary hemostasis.
Explain why DIC causes both thrombosis and hemorrhage.
Widespread clot formation consumes platelets and factors → then bleeding from depletion