POLYCYTHEMIADefinition: An abnormal increase in the amount Haemoglobin in the circulatory system eit

POLYCYTHEMIA

Definition: An abnormal increase in the amount Haemoglobin in the circulatory system either due to loss of plasma volume or increased numbers of erythrocytes.

THE THREE TYPES: 

1. Relative - In this type of Polycythemia the actual number of RBC’s within the circulatory system is not abnormal, however due to dehydration there is a loss of plasma volume increasing the haemoglobin concentration.
   
2. Transient - This is more common in horses and is caused by splenic contraction where concentrated RBC’s are ejected into the circulatory system from the spleen. Splenic contraction occurs in response to Epinephrine release which is a hormone response to anger, stress and fear.
   
3. Absolute - This is caused when the Bone marrow produces increases amounts of RBC’s. It is separated into primary and secondary. 
   

• Primary - Known as Polycythemia rubra vera. This is a myeloproliferative disorder and caused the bone marrow to produce an uncontrolled number of RBC’s.
• Secondary - Secondary polycythemia occurs in response to either an overproduction of EPO i.e. due to kidney cysts or overactive adrenals or in response to a physiologically appropriate release of EPO i.e. due to hypoxaemia. 

CLINICAL SIGNS:

Polycythemia is asymptomatic but with an increase PCV/haemaglobin concentration comes an increase in blood viscosity. This can cause weakness, lethargy and dyspnea, in addition splenomegaly and heptamegaly is common. Oxygen saturation should also be checked. Lastly patients with this condition can be at risk of thrombus and symptoms associated with this should closely monitored for. 

DIAGNOSIS

Through blood work should be carried out to establish the patients PCV, and to allow for underlying causes such as Liver disease to be found. Diagnostic imaging such as radiography and ultrasound are recommended again to establish any underlying disease.  

TREATMENT

The aim is to treat the disease which is causing the polycythemia. For example if there is a 100% accurate diagnosis of primary absolute then Myelosuppressive therapy is recommended. However in many patients ‘blood letting’ the removal of blood every few days is enough to control the condition. 

PROGNOSIS

A shortened life expectancy is common in these patients. But most live a good quality of life with regular phlebotomy and regular PCV checks.