By Dr. Becker
Anemia is a condition in which there are an abnormally low number of red blood cells called erythrocytes or hemoglobin in the blood.
Hemoglobin is a protein molecule inside red blood cells. Its job is to move oxygen in the blood to all the tissues in the body. As red blood cells age (they have an average lifespan of about two months) or are damaged, they are collected by the spleen and removed from circulation.
Part of the hemoglobin molecule is recycled to the bone marrow to be included in new red blood cells, while other parts are processed by the liver.
Common Causes of Anemia
There are three causes of anemia: blood loss, destruction of red blood cells (hemolytic anemia), and insufficient production of red blood cells (aplastic anemia), which is the cause of about 80 percent of feline anemia.
Anemia caused by blood loss can result from trauma, surgery, or another bleeding disorder that results in a sudden reduction in the overall numbers of circulating red blood cells. However, anemia from blood loss can also be the result of a slower, chronic condition, including bleeding in the GI tract due to ulcers, internal or external parasites, cancer, and a number of other conditions.
Hemolytic anemia is caused by the destruction or shortened lifespan of red blood cells, which means there is a low overall circulating red blood cell volume. This type of anemia can be either immune-mediated or non immune-mediated.
Autoimmune hemolytic anemia is a condition in which an animal’s body sees its own red blood cells as foreign invaders and sets out to destroy them. Non immune-mediated hemolytic anemia is the destruction of red blood cells by other means, including red blood cell parasites, hereditary diseases, toxins, or a low phosphorous level.
Aplastic anemia, which is insufficient production of red blood cells, is caused by several different disorders, including tumors of the bone marrow, chronic kidney disease, and other conditions that affect the production of red blood cells. Infections like parvovirus or Ehrlichia can cause this type of anemia, as well as chemotherapeutic agents, sulfa drugs, estrogens, and sometimes exposure to radiation and toxins.
Symptoms and Diagnosis
When a pet has an abnormally low volume of red blood cells and consequently insufficient hemoglobin to carry oxygen to the body’s tissues, he experiences oxygen starvation.
Symptoms can include weakness, lethargy, exercise intolerance, an elevated heart rate, pale mucous membranes (usually noticed in the mouth – the gums and/or tongue become pale pink to white), mental confusion, loss of appetite, rapid breathing, and collapse. If the animal is passing a large amount of digested blood from the GI tract, there will be a black tarry stool as well.
Anemia isn’t difficult to diagnose. Typical diagnostic tests include a complete blood count, a packed cell volume, and a serum biochemistry panel. A blood smear can be analyzed under a microscope to evaluate the structure of the red blood cells.
A urinalysis may also be performed, as well as a test to check for Ehrlichia canis if the patient is a dog.
Your vet may also do a coagulation panel, as well as a mucosal bleeding time test to evaluate your pet’s clotting ability. A fecal test may also be performed to check for occult blood loss, which is blood loss from the intestines.
A diagnosis of anemia doesn’t identify the underlying problem, however. There are several other tests that often must be run to determine the cause of the low red blood cell volume.
These tests can include an abdominocentesis to check for fluid or blood in the abdomen due to trauma, a bleeding disorder, a problem with the spleen, or a complication from a prior surgery. Other tests might include abdominal X-rays, an ultrasound, or an endoscopy to look inside the abdomen for the presence of tumors or ulcers.
There are also tests that can identify the presence of mycoplasma or Babesia in the blood. Sometimes a DNA test is done to look for genetic defects in susceptible breeds. And of course there are tests to determine if there’s cancer present in your pet’s body.
Treatment for Anemia Depends on the Underlying Cause
If you think your pet may be anemic, you should make an appointment with your veterinarian as soon as possible. Anemia can be life threatening, depending on what’s causing it.
Treatment goals for patients with anemia are to control bleeding, restore blood volume, find and resolve underlying causes of chronic blood loss, and provide supportive care.
Depending on the cause of the anemia, treatment options can include IV fluid therapy to increase blood volume; transfusions of packed cells, whole blood, platelets, or fresh frozen plasma; transfusions of bone marrow; antibiotics if infection is present; vitamin K1 for coagulation disorders or certain poisonings; GI protectants; anti-parasitic medications; potassium phosphate supplementation; or surgery to fix the source of the bleeding.
Rarely is anemia related to iron deficiency in pets, as it is in many women. Iron supplementation should be avoided, unless your pet is one of the very rare cases where actual iron deficiency is present.
Anemic pets must be carefully monitored while undergoing treatment.
Acute aplastic anemia can be reversed within a few weeks once the cause is identified. Chronic aplastic anemia is usually a more serious condition and more difficult to resolve.
Blood loss anemia can be resolved as soon as the source of the bleeding is identified and repaired. Anemia caused by cancer has a less optimistic prognosis and depends on the pet’s response to treatment for the cancer. Many causes of hemolytic anemia can be resolved once whatever is causing the destruction of the red blood cells has been identified.