|
|
| Comparative Coagulation |
|
|
|
Clinical Topics - Diagnostic Approach
|
| |
| 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. |
-
Clinical signs of secondary hemostatic disorders include subcutaneous
or intramuscular hematoma formation, hemoperitoneum, hemothorax,
prolonged bleeding at sites of injury.
-
Specific secondary hemostatic disorders and diagnostic tests:
-
| Rodenticide toxicity: |
aPTT, PT, vitamin K-dependent factors (II, VII, IX, X) |
| Liver failure: |
aPTT, PT, fibrinogen |
| Hemophilia: |
aPTT, factors VIII, IX |
|
|
