21 Petechiae and ecchymoses
Petechiae and ecchymoses represent superficial bleeding into the skin or mucous membranes. Petechiae are small pinpoint haemorrhages and ecchymoses are larger areas. Petechiae are more commonly identified in mucous membranes, especially the buccal and gingival mucosa, the prepuce and the vulva. Ecchymoses may be more evident following venepuncture. Ecchymoses are sometimes difficult to distinguish from cutaneous erythema on inspection; however, this is readily achieved by pressing a glass slide on to the affected area – an erythematous lesion will blanch but an ecchymosis will not. Petechiae and ecchymoses are rare in cats.
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
The possibility of spontaneous haemorrhage is said to arise when total platelet count falls below 30 × 109 platelets/litre. On peripheral blood smear examination, this equates approximately to two platelets per high power (×1000) field. However, it must be remembered firstly that this is only a guideline, and secondly that not all animals with this level of thrombocytopenia will necessarily suffer bleeding.
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.
Platelet function disorders may be inherited or acquired. Inherited thrombopathies have been identified in several dog breeds (e.g. the Bassett hound, the Otter hound, the American Cocker Spaniel) and also a small number of cats. Acquired disorders may potentially occur for example due to uraemia, liver disease or various drug therapies.
Von Willebrand disease (vWD) is the most common inherited bleeding disorder in dogs. This disease most commonly presents with bleeding from mucosal surfaces (e.g. epistaxis, melaena and haematuria) and excessive bleeding following surgery or other trauma. However, ecchymoses (and petechiae) may occasionally occur. Type I vWD (reduced but measurable levels of vWF) is the most common and is seen especially in the Doberman Pinscher.
Signalment may help to raise or lower the index of suspicion for certain differential diagnoses. In particular, ITP is seen most commonly in female dogs and an increased incidence is reported in a number of breeds (e.g. the Cocker Spaniel, poodles, the Old English Sheepdog); this disorder is relatively rare in cats.
The history in animals with petechiae and ecchymoses is variable depending on the underlying cause. Some animals have nonspecific signs such as lethargy and inappetence, and present primarily for investigation of bleeding. In other cases, other clinical signs associated with the primary disorder are more significant (e.g. jaundice with leptospirosis) and petechiae or ecchymoses are identified almost incidentally.
A complete medical history, with particular focus on vaccination, drug administration and travel, is essential, and all current or previous medical problems should be explored. In particular, the owner should be asked about any previous episodes potentially consistent with coagulopathy, as well as whether there is a history of excessive bleeding following surgical or nonsurgical trauma.
Physical examination findings vary in animals with petechiae or ecchymoses, depending on the extent and sites of the bleeding and the underlying disorder. In some cases, evidence of external haemorrhage is the most remarkable finding; in addition to petechiae or ecchymoses, there may also be epistaxis, gingival haemorrhage, subcutaneous haematomas and melaena on rectal examination (see Figure 9.1). Animals with gastrointestinal haemorrhage may suffer severe blood loss and may present with findings consistent with clinically significant anaemia (tachycardia, hyperdynamic pulses, tachypnoea; lethargy, depression). In a multisystemic disorder such as leptospirosis, evidence of bleeding is likely to be only one of the significant abnormal findings on physical examination.
Clinical Tip
An emergency database should be performed in all animals presenting with petechiae or ecchymoses. An indwelling intravenous catheter is likely to be required in most of these cases and the emergency database is therefore usually performed on blood obtained via the catheter at the time of placement. The emergency database must include peripheral blood smear examination as this is the most reliable means of identifying severe thrombocytopenia (see Ch. 3). Reduced serum total solids and manual packed cell volume are suggestive of anaemia secondary to haemorrhage, and a regenerative anaemia (anisocytosis, polychromasia, increase in nucleated red blood cells) may be seen on smear examination in such cases.
Animals with petechiae or ecchymoses primarily as a result of platelet dysfunction may have a normal platelet count or only mild thrombocytopenia. Platelet function is very difficult to assess reliably in routine practice but measurement of buccal mucosal bleeding time (BMBT) is typically used. The results of this test can be quite discrepant depending on the individual performing the test, the technique (including restraint) used, and the patient’s haematocrit. Nevertheless, a severely prolonged BMBT in an animal without severe thrombocytopenia is likely to suggest a clinically significant platelet function disorder, vWD or vasculopathy. Normal BMBT in dogs and cats is generally considered to be less than 4 minutes and less than 2 minutes, respectively.