Erythrocytosis

Question 1

Erythrocytosis

Answer 1

an 🡑 in RBC count +/or Hct

2 types:
- Relative Erythrocytosis = secondary to something + not a true 🡑 in circulating RBC mass
- Absolute Erythrocytosis = true 🡑 in circulating RBC mass

absolute further divided into primary + secondary
- secondary divided into appropriate + innapropriate

higher in sighthounds

Question 2

Relative Erythrocytosis

Answer 2

secondary to something + not a true 🡑 in circulating RBC mass
- dehydration (hemoconcentration)
- splenic contraction (physiologic erythrocytosis)
- endotoxemia (d/t fluid shifts)

Question 3

Primary Absolute Erythrocytosis

Answer 3

AKA polycythemia vera

autonomous (EPO-independent) proliferation of erythroid precurors resulting in elevated # of mature erythrocytes in peripheral blood

rare
considered a neoplastic condition

diagnosis of exclusion 🡒 r/o secondary erythrocytosis

Question 4

Secondary Absolute Erythrocytosis

Answer 4

d/t appropriate or inappropriate 🡑 secretion of EPO

Appropriate = hypoxia of normal tissues present + driving EPO release

Inappropriate = hypoxia not present yet EPO being released

Question 5

Appropriote Secondary Absolute Erythrocytosis

Answer 5

🡑 EPO production secondary to hypoxia
- cardiac disease w/ L-to-R shunting of blood
- diffuse lung disease
- moving from low to high altitude
- some cats with hyperthyroidism
- persistent methemoglobinemia

Question 6

Inappropriate Secondary Absolute Erythrocytosis

Answer 6

🡑 EPO production in absence of hypoxia
- EPO-secreting renal tumor or renal lesions (rare)
- non-renal lesions

Question 7

Differentiation of Appropriate v Inappropriate Erythrocytosis

Answer 7

check arterial blood PaO2
- should be low in appropriote

diagnostic imaging to asses for:
- cardiac +/or pulmonary disease
- renal lesions/tumors + other masses

plasma EPO concentration measurement:
- expect 🡑 with secondary
- should be normal/low with primary
- however lots of overlap limits diagnostic usefulness + testing not available