Preliminary Evaluation: The goal of initial examination is to differentiate bleeding caused by injured or diseased blood vessels from that caused by a systemic hemostatic disorder. A combination of clinical signs, history, and screening tests (platelet count, bleeding time, coagulation panel) will help make this distinction.
Blood Vessel Disorders
Blood vessel disorders are primarily diagnosed by inspection, either visually or using ancillary diagnostics (i.e., endoscopy, radiography, ultrasonography, or biopsy). Clinical signs of bleeding from damaged vessels depend on the size of the injured vessel.
- Large vessel disorders are characterized by hemorrhage from a single anatomic site, often with blood loss anemia.
- Small vessel disorders (vasculopathies) rarely cause anemia. Vasculopathies typically cause multisystemic signs including cutaneous ecchymoses, uveitis, glomerulonephritis, and pulmonary or peripheral edema.
Systemic Bleeding Disorders
Systemic bleeding disorders are classified as defects of either primary hemostasis (platelet plug formation) or secondary hemostasis (fibrin clot formation).
- Primary hemostatic disorders are caused by failure of platelet plug formation due to quantitative or qualitative platelet disorders, or due to von Willebrand factor deficiency.
- Clinical signs of primary hemostatic disorders include petechiae, mucosal hemorrhage, prolonged bleeding at sites of injury.
- Specific primary hemostatic disorders and diagnostic tests: Thrombocytopenia: platelet count, platelet estimate from blood smear Platelet dysfunction: in vivo bleeding time, platelet aggregation, drug history and metabolic profile
- Secondary hemostatic disorders are caused by failure of fibrin clot formation due to deficiency of one or more coagulation factors.
||aPTT, PT, vitamin K-dependent factors (II, VII, IX, X)
||aPTT, PT, fibrinogen
||aPTT, factors VIII, IX