Determining the cause in a patient presented for excessive bleeding can be a diagnostic challenge. In addition to a thorough physical examination, a recent and prior history or any relevant family history should be obtained. If the animal has been neutered or undergone some other type of surgery without evidence of abnormal bleeding, this points towards a recent acquired cause of hemorrhage rather than a congenital or hereditary problem. Breed experience [e.g. Doberman pinschers with their high prevalence of von Willebrand’s disease (vWD)] is also important. Use of drugs that impair hemostasis, potential toxin exposure such as to rodenticides, or vaccinations within the previous 30 days may be inciting causes. Pre- existing liver or kidney disease could play a role as well. Asymptomatic carriers of bleeding diseases such as vWD can express the trait if some other precipitating stress event or exposure occurs. Animals of mostly white coat color or dilutional pigmentation may be at increased risk to bleed excessively when hemostatically challenged because of their relative platelet dysfunction.

The character of bleeding presents valuable diagnostic clues. Petechial or ecchymotic hemorrhages are typical of thrombocytopenia; mucosal surface bleeding and excessive hemorrhage or oozing from surgical sites is seen in platelet defects (quantitative and/or qualitative) and vWD; whereas, large surface hematomas and protracted bleeding characterizes congenital disorders like the hemophilias and severe acquired problems such as rodenticide toxicosis and disseminated intravascular coagulation (DIC).

Diagnostic evaluation begins with a basic coagulation profile (platelet count, PT and APTT, fibrinogen level and test for FDP) to which a vWD assay can be added as needed. The bleeding time may also be a valuable tool and can be measured by the mucosal (buccal) method with a template device or by transecting a toe nail (see below). The buccal bleeding time primarily measures platelet function and can therefore be normal in patients with unstable primary hemostatic plugs or defects in fibrin formation. The toe nail method offers a more complete assessment of hemostasis, although it can be difficult to standardize.

When significant thrombocytopenia is present (platelet counts < 50,000/pl), the laboratory can assess platelet size and volume. Predominantly small platelets (MPV < 5.0 fl) are characteristic of immune-mediated platelet destruction, whereas mostly large platelets (MPV > 9.2 fl) signify active thrombopoiesis and tend to be more adhesive. Please indicate on your Test Request Form or by phone request that you wish to have platelet size evaluated, if the platelet count is very low.

With the animal in lateral recumbency, either awake or anesthetized, cut one or more toe nails too short with a sharp guillotine-type toe nail clipper. Make a clean transection of the nail just into the quick (becomes reproducible with practice). Let the nail bleed freely undisturbed and time until bleeding stops. Normal bleeding times are up to 5 minutes in dogs and 2 1/2-3 minutes in cats. A prolonged bleeding time or rebleeding once it has stopped is considered abnormal. Bleeding times measured by this technique are sensitive to defects in vascular contraction, platelet function and coagulation. This test can be useful for:

• pre-surgical assessment of bleeding potential;
  
• evaluation of response to therapy in bleeding animals;
  
• determination of degree of bleeding risk (e.g. slight prolongation of 1-3 minutes may be manageable conservatively without transfusion; moderate to severe prolongation of 3 or more minutes usually requires treatment before surgery or to alleviate clinical signs; bleeding time endpoints over 10 minutes are significantly prolonged and require transfusional therapy).