Hemorrhage
Basic Information 
Epidemiology
Species, Age, Sex
Horses of any age are susceptible to blood loss because of a number of causes; however, vessel rupture and urolithiasis are more common in older horses, and idiopathic hematuria is limited to males.
Genetics and Breed Predisposition
Genetic platelet disorders and coagulation factor dysfunction have been identified in horses, as well as a genetic predisposition to granulomatous gastrointestinal proliferation and urolithiasis.
Clinical Presentation
Disease Forms/Subtypes
Hemorrhage can be classified by location (internal or external), duration (acute or chronic loss), vessel size (capillary and venuole or arteriole versus larger vessel), and cause (coagulation disorder versus traumatic vessel disruption)
History, Chief Complaint
Etiology and Pathophysiology
• Traumatic vascular disruption occurs because of an injury that mechanically opens a vessel or vessels (caused by injury, disease, infection, or neoplasia) with a normal coagulation system that is unable or slow to repair the defect because of vessel size and blood pressure, repeated trauma, or systemic inflammation.
• Hemostatic bleeding disorders may occur by one of two pathways:
Primary hemostatic defects involve either a genetic failure of the platelets to functionally occlude a vascular leak or thrombocytopenia, which reduces effective platelet numbers. Both result in capillary and small vessel hemorrhage (petechia, ecchymosis).
Secondary hemostatic issues are related to coagulopathies caused by congenital defects, vitamin K deficiencies, hepatic disease, drug toxicity, envenomation, poisons, or consumption of coagulation factors (ie, disseminated intravascular coagulation). This results in overt hemorrhage into body cavities or externally.
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