21 Petechiae and ecchymoses
Causes of Petechiae and Ecchymoses
Petechiae and ecchymoses are typically the result of severe thrombocytopenia, platelet function disorders, or a localized or systemic vasculopathy. Thrombocytopenia is the most common cause in companion animals, and there may be other signs of haemorrhage such as epistaxis, melaena (see Figure 9.1), haematuria and active gingival bleeding.
Clinical Tip
• Traditionally petechiae and ecchymoses were said to be the result of disorders affecting so-called primary haemostasis, while conditions involving coagulation factor deficiencies (e.g. anticoagulant rodenticide intoxication, liver failure) were said to cause disorders in secondary haemostasis.
• Coagulation factor disorders typically present differently from platelet or vascular disorders, with bleeding occurring more commonly into body cavities or as haematomas rather than as mucosal or cutaneous haemorrhage; these animals are also more likely to bleed excessively following venepuncture.
• Although in recent years it has been shown that the traditional classification of coagulation is too simplistic in vivo, the distinction remains very important to avoid misdiagnosis and inappropriate investigation. In particular, the author is aware of many dogs with petechiae that have been erroneously investigated or treated for anticoagulant rodenticide intoxication that is extremely unlikely to present in this way.
Thrombocytopenia
In the author’s experience, clinically significant haemorrhage associated with thrombocytopenia is most commonly the result of primary (idiopathic) immune-mediated thrombocytopenia (ITP) (see Ch. 33). It is also noteworthy that thrombocytopenia secondary to haemorrhage is extremely unlikely to be sufficiently severe as to induce further bleeding.
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