Von Willebrand's disease
Von Willebrand's in dogs results from a lack of functional von Willebrand factor (vWF), a glycoprotein that is involved in platelet adhesion to the vessel wall during formation of the primary hemostatic plug. This leads to abnormal primary hemostasis (platelet plug formation) and prolongation of bleeding time. The release of vWF is stimulated by an assortment of other substances such as histamine, fibrin, estrogen, collagen, platelet-activating factor, thrombin, and adenosine diphosphate. In areas with a high blood flow rate, vWF is necessary for the platelets to adhere to the subendothelium. Platelets subsequently bind to vWF and adhere to the vessel wall.
Clinically, this disease is categorized, based on clinical symptoms, from Type 1 (mild) through to type 3 (severe).
Affected dogs usually present with buccal bleeding, commonly observed in dogs after chewing bones or after removal of deciduous teeth. Incidental signs are comonly observed following routine desexing, with increased bleeding intra-operatively or post-operatively. Other signs include hematemesis and bloody diarrhea.
An abnormal presentation has been reported in the Doberman where increased microvascular bleeding within muscle may lead to heterotopic osteochondrofibrosis, characterized by multiple intramuscular masses composed of osseous, chondrous or fibrous tissue in or around the muscles of the hip.
The classification of VWD is used to recommend therapeutic protocols:
- Type I - most common form
- Type II - primarily in German Short-Haired Pointer and German Wire-Haired Pointer.
- Type III - rare
Emergency treatment of bleeding episodes is accomplished by whole blood transfusion. Long term maintenance of affected dogs involves use of Vit-K oral supplementation.
Vasopressin is an alternative treatment for vWD-associated bleeding episodes, given at 1 µg/kg SQ; however, Type I vWD responds poorly to long-term vasopressin therapy.
Drugs with antiplatelet or anticoagulant effects should be avoided, including nonsteroidal anti-inflammatory drugs, estrogens, cytotoxic medications, heparin, coumadin, plasma expanders and sulfonamide antibiotics.
- Cornell Uni
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