Page 561 - Problem-Based Feline Medicine

25 – THE CAT WITH POLYCYTHEMIA 553

blood cell mass. Clinical signs may include dyspnea, lethargy, weakness, a gallop rhythm,
heart murmur and arrhythmia. Mucous membranes may be pale or cyanotic with prolonged
capillary refill time.
ANOMALY

● Congenital heart disease* (p 561)
Congenital cardiac anomalies associated with right to left shunting, e.g. tetralogy of Fallot,
reverse patent ductus arteriosus, and atrial or ventricular septal defects may cause secondary
polycythemia in young cats. There may be a history of lethargy and stunted growth, and on
clinical examination, dyspnea, cyanosis and a heart murmur may be noted. PCV is often
markedly elevated (> 60%).
● Renal space-occupying mass
Renal conditions such as renal cysts and hydronephrosis have been associated with inappropri-
ate erythrocytosis secondary to increased erythropoietin production, but these are very rare.
Kidneys are unilaterally or bilaterally enlarged on abdominal palpation, and there may be asso-
ciated clinical signs of renal disease such as polyuria and polydipsia.
NEOPLASTIC

● Polycythemia vera*(p 563)
Primary polycythemia is caused by a myeloproliferative disorder, similar to polycythemia vera in
humans. There may be a history of bleeding, seizures, polydipsia and polyuria, and physical exam-
ination reveals dark pink mucosa with a PCV often exceeding 60%. Circulating erythropoietin lev-
els are normal or low. This condition is very rare in cats.
● Neoplasia (p 565)
Neoplasia of a wide variety of organs including the kidneys, liver, adrenal gland, female
reproductive tract and central nervous system have been associated with inappropriate poly-
cythemia. The condition is characterized by increased circulating erythropoietin levels without
a hypoxic stimulus. Impaired renal blood flow secondary to a space-occupying mass, or tumor
secretion of erythropoietin or erythropoietin-like substances have been hypothesized as possi-
ble causes of erythrocytosis. Clinical signs relate to the type of tumor involved and its anatomi-
cal location.

METABOLIC
● Dehydration*** (p 557)
Derangement of fluid balance from a variety of causes is the most common cause of poly-
cythemia in cats. Polycythemia occurs most commonly when excessive fluid loss through the
gastrointestinal tract (vomiting or diarrhea) or kidney (diabetes mellitus or renal
failure) is coupled with inadequate fluid intake. Typically there is depression and anorexia,
and signs that relate to the underlying condition such as polyuria, polydipsia, vomiting or diar-
rhea. Skin tents on pinching, mucous membranes are dry, and may have delayed refill.
Accompanying laboratory abnormalities include increased total protein, increased urine specific
gravity and pre-renal azotemia.

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