Page 562 - Problem-Based Feline Medicine

554 PART 8 CAT WITH ABNORMAL LABORATORY DATA

continued

● Hyperthyroidism** (p 560)
Hyperthyroidism may be associated with a mild increase in PCV, possibly from a direct effect of
thyroxine on erythrocyte precursors. Affected cats are usually older (> 8 years), with a history of
weight loss despite a robust appetite. Associated clinical signs include irritable behavior, tachycar-
dia, sometimes with a gallop rhythm, polyuria, polydipsia and often chronic vomiting.

● Severe obesity (Pickwickian syndrome) (p 568)
Morbid obesity may predispose to tissue hypoxia from inadequate alveolar ventilation because of
fat accumulation in the thorax and compression of upper airways. Blood O saturation levels are
2
low (<92%) and there are slightly to markedly increased circulating levels of erythropoietin.
PHYSICAL

● High altitude (p 568)
Decreased O levels in the atmosphere at high altitudes may stimulate increased renal erythropoi-
2
etin production in response to tissue hypoxia. The cat is otherwise clinically normal, although
there may be mild dyspnea with a fast, shallow respiratory pattern. Circulating erythropoietin lev-
els are elevated.
PSYCHOLOGIC
● Stress-induced splenic contraction (p 567)
The stress response in cats may include splenic contraction, with a resultant infusion of stored
splenic erythrocytes into the circulation. Affected cats usually have an appropriate history and may
have other accompanying signs such as dilated pupils and behavioral changes. Hemoconcentration
caused by stress is usually mild and transient.
IATROGENIC

● Excessive blood transfusion or overdose of exogenous erythropoietin (p 564)
This is a potential, although previously unreported, cause of polycythemia. The diagnosis is made
with an appropriate history and clinical signs of erythrocytosis such as weakness, injected mucous
membranes and neurological signs.
IMMUNE

● Acute systemic anaphylaxis (p 566)
Acute systemic anaphylaxis results from an extremely rapid and overwhelming immune reaction to
a foreign antigen. It may cause hemoconcentration, most likely from a combination of fluid loss
caused by increased vascular permeability, and splenic contraction in response to acute shock.
There should be a history of exposure to a foreign antigen, usually protein. Anaphylaxis may occur
on the first exposure to the inciting antigen. Clinical signs include acute dyspnea, collapse, pale
mucus membranes and other signs of hypotensive shock.
INFLAMMATION
● Chronic pulmonary disease* (p 562)
Chronic pulmonary disease such as feline asthma/bronchitis complex may cause tissue hypoxia,
resulting in increased erythropoietin production and erythrocytosis. There is usually a history of
chronic coughing, with dyspnea and lethargy in more severe cases. Clinical signs include crackles
and wheezes on thoracic auscultation.