Page 573 - Problem-Based Feline Medicine

25 – THE CAT WITH POLYCYTHEMIA 565

Serum erythropoietin levels are normal or elevated,
Diagnosis
and blood O saturation levels are normal.
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The diagnosis is made using a combination of an appro-
priate history and clinical signs.
Differential diagnosis
NEOPLASIA Secondary inappropriate polycythemia must be differ-
entiated from relative polycythemia in dehydration,
Classical signs secondary polycythemia due to hypoxia, and from
primary polycythemia.
● Signs are referable to the causative space-
● In neoplastic conditions, there is a normal plasma
occupying mass.
● Mucosae may be dark pink. protein concentration, normal blood O saturation
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and normal or increased serum erythropoietin
● Signs of hyperviscosity, e.g. tortuous
concentration. This differentiates secondary inap-
retinal vessels, seizures, bleeding propriate polycythemia associated with neoplasia
diatheses, polyuria, polydipisia.
from other conditions causing polycythemia.
Pathogenesis Treatment

It is hypothesized that renal and other visceral tumors Treatment should be directed at the tumor, which is the
may secrete erythropoietin or an erythropoietin-like underlying cause of the polycythemia.
substance, resulting in erythrocytosis. While these Polycythemia may reoccur if metastatic foci secrete
tumors have been reported to cause polycythemia in erythropoietin or an erythropoietin-like substance.
humans and dogs, they are yet to be reported as a cause
of polycythemia in the cat.
Prognosis
This kind of polycythemia is secondary to another
pathological condition and inappropriate, since The prognosis depends on the underlying cause of
blood O saturation levels are normal. the polycythemia. The prognosis with neoplasia varies
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according to the tumor type.
Clinical signs

Clinical signs are referable to the underlying neoplasia RENAL SPACE-OCCUPYING MASS
and polycythemia.
Classical signs
Mucus membranes are dark pink.
● Signs are referable to the causative space-
Signs of hyperviscosity include tortuous retinal vessels,
occupying mass.
seizures and other CNS signs, and intermittent bleeding
● Dark pink mucosae.
diathesis.
● Signs of hyperviscosity, e.g. tortuous
retinal vessels, seizures, bleeding
Diagnosis diatheses, polyuria, polydipisia.
● ±Signs of renal insufficiency, such as
Erythrocytosis associated with neoplasia is diagnosed
azotemia, reduced urine specific gravity,
when there is a combination of marked erythrocytosis
polydipsia and polyuria.
(PCV > 60), normal or increased serum erythropoietin
levels, normal plasma protein concentration, and nor-
mal blood O saturation levels. Pathogenesis
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Visceral tumors are diagnosed ideally by abdominal A space-occupying renal mass such as a cyst, hydro-
ultrasound, although intravenous pyelography may nephrotic disease or tumor may induce local tissue
also be a valuable imaging technique for renal masses. hypoxia, stimulating renal oxygen sensors, resulting in