Overcoming the diagnostic and therapeutic challenges of canine immune-mediated thrombocytopenia - Veterinary Medicine
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Overcoming the diagnostic and therapeutic challenges of canine immune-mediated thrombocytopenia
Determining that the immune system is the cause of a dog's decreased platelet count can be difficult. These clinicians walk you through the diagnostic and treatment process so you can help patients with this life-threatening bleeding disorder.


Clinical presentation

Table 1. Clinical Signs Typical of Primary and Secondary Hemostatic Disorders
Dogs with immune-mediated thrombocytopenia are often not presented for evaluation of bleeding, but rather for nonspecific clinical signs such as lethargy, weakness, or anorexia.1,2,6 Some affected dogs are asymptomatic. In these dogs, a low platelet count on a CBC may be the first indication of immune-mediated thrombocytopenia. Dogs with secondary immune-mediated thrombocytopenia could present for evaluation of clinical signs related to the underlying disease (e.g. peripheral lymphadenopathy with lymphoma or dyspnea with disseminated histoplasmosis).6 Other dogs with immune-mediated thrombocytopenia have signs of hemorrhage with a history of otherwise being apparently healthy.1 Unexpected hemorrhaging after trauma or routine surgery, is also a manifestation of immune-mediated thrombocytopenia.1,7

1. Petechial hemorrhages on the mucous membranes of a dog with immune-mediated thrombocytopenia.
Bleeding related to immune-mediated thrombocytopenia is typical of that expected with primary hemostatic disorders (Table 1). Bleeding from mucous membranes may cause gingival, nasal, conjunctival, preputial, penile, or vaginal hemorrhage.1,6 Petechiae or ecchymotic hemorrhages on the mucous membranes and skin, especially on the ventral abdomen, are typical (Figure 1).1,2,6,7 Mucous membranes may be pale if concurrent anemia is present. Gastrointestinal (GI) hemorrhage can manifest as hematemesis, melena, or hematochezia.1,6,7 Hyphema and retinal hemorrhages may be present, possibly causing blindness.1,2,7 Hematuria may result from hemorrhage into the urinary tract. Often, dogs with immune-mediated thrombocytopenia are otherwise clinically stable.1

Life-threatening hemorrhage can develop when bleeding occurs into the central nervous system, GI tract, or pulmonary parenchyma.2,13-15 Because of the potential for bleeding in any dog with immune-mediated thrombocytopenia, consider each case a serious and potentially life-threatening disorder, regardless of the signs on presentation. Severe GI hemorrhage is the predominant cause of death in dogs with acute immune-mediated thrombocytopenia.1

History and physical examination

Evaluation of patients with immune-mediated thrombocytopenia begins with a thorough history to identify suspected underlying causes such as medications or recent vaccinations (e.g. given within the previous month).8 Identify and discontinue the administration of medications that decrease platelet function (e.g. aspirin). Ask about travel to areas endemic for diseases such as ehrlichiosis and dirofilariasis, and, in endemic areas, inquire about the use of flea, tick, and heartworm preventives and the prior presence of ticks on the animal.8 Signs of other concurrent illness may be identified in the history or during the physical examination. Determine the location, duration, and severity of bleeding episodes. Also obtain a history regarding previous blood transfusions.

Perform a complete physical examination, including an ophthalmic examination. Note any evidence of abnormal hemostasis. A rectal examination may be required to obtain feces to evaluate for melena. Mild fever is present in some dogs with immune-mediated thrombocytopenia.1,13 Splenomegaly may be present,2,13 and some authors suggest that finding splenic enlargement on physical examination increases the likelihood of a concurrent disorder.1,2


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