Overproduction of Red Blood Cells in Dogs

Red blood cells, also known as erythrocytes, are used to carry oxygen to the tissues where it is used for cellular metabolism.  Too many red blood cells is known as polycythemia and can result in the blood being too thick and therefore, can interfere with the heart’s ability to deliver oxygen throughout the body.  Your veterinarian will need to run a series of diagnostic testing to determine your dog’s condition in order to begin treatment.  The prognosis of recovery from this condition is guarded to poor.

An overproduction of red blood cells can be a life threatening condition for your dog.  If he is lethargic, having trouble breathing or has brick red gums, it should be treated as a medical emergency; you need to get him to a veterinarian immediately.

Symptoms of this condition may include:

• Red mucous membranes
• Increased blood pressure
• Mental dullness
• Dyspnea 
• Thickened blood/increased viscosity
• Increased blood volume 
• Heart unable to deliver oxygen throughout the body
• Decreased oxygenation of the brain
• Congestive heart failure 

Types

A healthy animal should hallways have a constant number of red blood cells circulating in his system.  This means his oxygen carrying capacity should always be constant as well.  When there are too many red blood cells in circulation, it is referred to as polycythemia.  Bone marrow is what produces red blood cells and releases them into circulation.  If there is an overproduction of red blood cells, it is known as erythrocytosis.

There are two different versions of erythrocytosis: a primary version and secondary version each with different causes.  Polycythemia vera is a type of clonal disorder of stem cells thought to results is the overproduction of red blood cells; it is known as a primary form of erythrocytosis. One cause of this condition is thought to be excess secretion of cytokines and stimulatory glycoproteins from tumor cell clones.  Secondary erythrocytosis is typically caused by increased erythropoietin levels.   This type can be seen as lung disease, congestive heart failure, abnormalities of blood circulation and decreased arterial oxygen saturation.

When you arrive at the veterinary clinic, your veterinarian will begin by performing a full physical exam on your dog.  She will want to examine him entirely to note all the symptoms he is experiencing.  She will also collect a verbal history from you about his your dog’s condition.  She will want to know what symptoms he has been experiencing, when they started, if the symptoms have been progressing or worsening, if any other pets in the home are experiencing similar symptoms and related questions. Your veterinarian may need to come to her diagnosis by a rule out process.  There are similar conditions that can cause the symptoms associated with overproduction of red blood cells.  She will need to rule out severe dehydration, hyperadrenocorticism, arteriovenous shunts, and various cardiac and pulmonary diseases. 

For her diagnostic process, she will start with blood work.  A complete blood count and chemistry panel will indicate the increased red blood cells within circulation of the blood stream.  It will also give information on the levels of the internal organ function.  It will indicate if any organs are going into failure.  She will also want to proceed with radiographs of heart and lungs.  This will allow her to view both for changes such as enlargement and for fluids within or around it.  She may also want to look at the heart and lungs with an ultrasound.  This will give her more of a live view of how the heart is pumping.   She may also want to evaluate the kidneys with the ultrasound to rule out the presence of a renal mass.

Your veterinarian will want to continuously check the oxygen content within your dog’s blood with an SPO2 meter.  Additionally, other heart and lung specific tests and tests to evaluate the bone marrow will be performed to evaluate your dog’s status and to differentiate if your dog’s condition is primary erythrocytosis or secondary.

Treatment will be started immediately as this can be an extremely serious condition.  Your veterinarian will need to remove excess red blood cells via phlebotomy until the hematocrit count returns to a normal level.  During this process, she will replace the removed blood with fluids.  This will thin out the blood to a proper level and keep your dog from becoming dehydrated or anemic. 

She may also use medications such as chlorambucil or hydroxyurea for your dog’s treatment.  She may administer other therapies and medication in accordance with your dog’s needs.  For treatment to be as successful as possible, she must diagnose and treat the underlying disease if applicable.

In some cases of dog’s with an overproduction of red blood cells, chemotherapy can be utilized to control the overproduction successfully for months to years.  In other cases, chemotherapy does not have the desired effect on the dog and is therefore not used in treatment.

This condition can be life threatening if not treated immediately.  The sooner your dog receives treatment the better his chances of recovery. Your veterinarian will do what she can to stabilize your dog’s condition as soon as you arrive at the clinic.  However, even with all the treatments available to the veterinarian, your dog’s prognosis of recovery is guarded due to the severity of the condition.