DIC: Diagnosing and treating a complex disorder - Veterinary Medicine
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DIC: Diagnosing and treating a complex disorder
This bleeding disorder, which can develop from multiple conditions, isn't necessarily a death sentence. Depending on the degree of the problem and the timeliness of the diagnosis, patients can be treated successfully.


VETERINARY MEDICINE


DIAGNOSIS

The diversity and complexity of DIC make establishing a diagnosis difficult. Always consider DIC in patients with an unexplained sudden onset of hemorrhage, thrombosis of one or more organ systems, or a disease commonly associated with DIC. It is impossible to differentiate between a patient with an early platelet consumptive process that will soon develop acute DIC and a patient with chronic DIC. So it is important to screen patients that present with disease associated with DIC before signs of organ failure or overt hemorrhage occur. Early recognition facilitates early therapeutic intervention and possibly prevents acute DIC.

Clinical signs and laboratory tests

The clinical features of DIC are nonspecific and depend on the degree of coagulation and organ systems affected. Most patients present for evaluation of the primary disease and are rarely bleeding spontaneously.1 For patients with evidence of hemorrhage, consider other acquired bleeding disorders. Even if you suspect DIC, a definitive diagnosis relies on evaluating laboratory test results.


Table 2. Test Results to Help Differentiate Among Acquired Bleeding Disorders
Not only is there no highly specific test for DIC, but some tests lack sensitivity. In addition to a complete blood count, a serum chemistry profile, and urinalysis, the laboratory tests for evaluating any hemostatic disorder, including DIC, ideally consist of a prothrombin time (PT), an activated partial thromboplastin time (APTT), a platelet count, fibrinogen concentration measurement, fibrin degradation products (FDPs) measurement, a D-dimer assay, antithrombin activity measurement, and a blood smear evaluation (Table 2).10

Clotting times
When evaluating a patient that you suspect has DIC, it is important to remember that thrombin or plasmin may predominate or both may contribute to initiating DIC. If excessive thrombin is driving DIC (peracute form), organ damage secondary to microvascular thrombosis may be evident as renal impairment, pulmonary dysfunction, gastrointestinal dysfunction, or neurologic deficits. Although of uncertain clinical relevance, the APTT and PT may be decreased or normal depending on the chronicity of the primary disease.8 A more sensitive test for acute thromboembolism may be a D-dimer concentration in dogs.9,11 If plasmin is driving DIC (acute form), secondary hemostatic abnormalities are usually present and clotting times are prolonged. The latter is due to plasmin's role in inactivating factors V, VIII, IX, and XI. If both thrombin and plasmin are driving DIC (chronic form), clinical evidence of overt thrombosis and hemorrhage may not be present, so making a diagnosis is challenging.

If a patient's clotting times are normal and an underlying disease is identified that predisposes the patient to DIC, perform serial platelet counts and measure the fibrinogen concentration. In patients with microvascular thrombosis, thrombocytopenia is expected because platelet consumption usually exceeds bone marrow thrombopoiesis (depending on chronicity). And because thrombin converts fibrinogen into fibrin, the fibrinogen concentration is expected to be low in patients with DIC. However, fibrinogen is an acute phase protein, and with chronic inflammation it may be elevated in patients with DIC.5 Furthermore, dogs have a tremendous capacity to replenish fibrinogen.

One study revealed a prolonged APTT in 87% of dogs with DIC, a prolonged PT in 80%, thrombocytopenia in 80%, and a low fibrinogen concentration in 61%.12 Another study revealed a prolonged APTT in 100% of cats with DIC, a prolonged PT in 71%, thrombocytopenia in 57%, and a low fibrinogen concentration in 5%.1 Thrombocytopenia and low fibrinogen concentrations are not specific for DIC.

Platelet count
It is important to evaluate sequential platelet counts. Counts that decrease over time are consistent with a consumptive process. Our clinic evaluates for evidence of megathrombocytosis (increased mean platelet volume). Our clinical impression is that megathrombocytosis is a sensitive indicator of immune-mediated or consumptive coagulopathy even with mild serial decreases in platelet counts.


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Source: VETERINARY MEDICINE,
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