Primary polycythaemia in a dog

A 7-year-old, crossbred, desexed bitch had a fluctuating illness of more than 6 months duration, with signs of inappetence, reduced exercise tolerance, restlessness, panting, black diarrhoea, and red eyes and ears. Haematological examination disclosed persistent polycythaemia, reticulocytosis, normoblastaemia , and normal total plasma protein concentration when not dehydrated. Splenomegaly was present, but there was no evidence of significant pulmonary, cardiac or renal disease on physical, radiographic or electrocardiographic examination. Further investigations revealed normal arterial Po2 and oxygen saturation, and increased total erythrocyte volume. Primary polycythaemia was diagnosed. The dog was rendered anaemic by bleeding, then treated with a single injection of radioactive phosphorus. The patient has had no recurrence of signs and remains well 50 months later.