Bleeding disorders in dogs 1. Inherited disorders

BLEEDING disorders are common in dogs, can be inherited or acquired, and are associated with either single or multiple defects in the haemostatic response. The clinical nature of the bleeding can sometimes be helpful in differentiating between primary (platelet or vascular) and secondary (coagulation) defects. In addition, laboratory testing aids in the detection and differentiation of bleeding disorders. Tests such as the buccal mucosal bleeding time (BMBT) and the activated clotting time (ACT) can be performed in-house by the veterinary surgeon, and provide a rapid means of assessing the integrity of the primary and secondary haemostatic responses, respectively. Other haemostatic screening tests such as the platelet count, partial thromboplastin time (PTT), prothrombin time (PT) and thrombin clotting time (TCT) are readily available through veterinary diagnostic laboratories, and are often useful in identifying the nature of the haemostatic defect; these tests are performed on citrated plasma harvested from a carefully collected blood sample submitted according to the laboratory's directions. This article reviews the pathogenesis, clinical and laboratory diagnosis, and treatment of the major inherited haemostatic disorders that have been described in the dog. The more common acquired causes of excessive bleeding in the dog will be discussed in the next issue.