Overview of Anemia in Dogs
Anemia is defined as a low red blood cell count and can be caused by a number of different processes, including blood loss, red blood cell destruction, and inadequate red blood cell production.
The aforementioned categories of anemia can be caused by trauma, cancer, immune-mediated disease, which is a disease in which the body attacks its own cells or organs, infectious disease, toxins, genetic defects, inflammatory disease, iron deficiency, drug reactions, kidney failure, and generalized chronic (long term) illness.
Because there are so many different types and causes of anemia, there is no gender or age predisposition for anemia. Individual disease processes may be more common in certain age groups and breeds, so it is important to characterize the type of anemia present.
The impact of anemia on your pet will depend on the cause of the anemia as well as the severity of the anemia. Additionally, animals with a sudden onset of anemia may be clinically sicker than animals with chronic anemia. This is due to the fact that animals can become partially adapted to the anemia over time, and may feel relatively good in spite of the anemia.
What to Watch For
Increased respiratory rate
Episodes of collapse
Evidence of blood loss
Blood in the urine or feces
External blood loss
Yellow discoloration of the skin
Depending on the underlying cause of the anemia, your pet may show some or all of these signs. Some pets may not show any signs at all.
Diagnosis of Anemia in Dogs
History and physical exam
Complete blood count (CBC)
Other possible diagnostic tests based on initial findings:
Abdominal radiographs (x-rays)
Thoracic (chest) radiographs
Coagulation profile (clotting tests)
Bone marrow aspirate
Specific tests for infectious diseases
Tests of immune function/dysfunction
Treatment of Anemia in Dogs
The most important component of treating anemia is treating the underlying disease process that is causing the anemia. If anemia is severe, patients might require a blood transfusion, or multiple transfusions.
Home Care and Prevention
Administer all medications as prescribed by your veterinarian. Monitor your pet for pale gums, extreme weakness, anorexia, increased respiratory rate, or recurrence of any of the original clinical signs.
There are no specific means of preventing anemia, since it can be caused by numerous factors.
In-depth Information on Anemia in Dogs
Anemia can be a primary problem, which significantly affects your pet’s well being, or it can be secondary to other disease processes, in which case it might or might not cause important clinical illness. The most common causes of severe anemia in dogs include blood loss and red blood cell destruction. External blood loss is generally caused by trauma. Significant internal blood loss in dogs most often occurs due to either bleeding into the intestinal tract or bleeding into the abdominal cavity.
Vehicular trauma is a common cause of bleeding into the abdomen. This results from damage to the liver and/or spleen and sometimes the kidneys. This type of blood loss cannot be seen, but can be life threatening and will often result in collapse. Tumors associated with the liver and spleen can also cause significant bleeding into the abdomen. A third common cause of bleeding into the abdomen is rat poison ingestion, which inhibits normal blood clotting.
Bleeding into the intestinal tract will often result in the formation of black, tarry stools. This can be secondary to cancer, severely low platelet counts (platelets are the blood cells that aid in blood clotting), or severe inflammatory disorders of the gut.
Red blood cell destruction commonly occurs in dogs due to an immune-mediated disease in which the body destroys its own red blood cells. This type of anemia is called hemolytic anemia. Hemolysis may also be caused by cancer, exposure to certain drugs, vaccine reactions, heavy metal toxicity (zinc, copper), and infectious diseases, several tick-borne diseases in particular.
Any chronic illness can cause anemia. This type of anemia is usually mild to moderate, and does not significantly impact the pet in most cases.
Causes of Canine Anemia
As discussed, there are many causes of anemia and therefore many different clinical signs. Other diseases that may cause signs of generalized weakness, collapse and increased respiratory rate include:
Respiratory tract disease. Diseases of the lungs and/or airways may cause an increased respiratory rate and possible collapse, if severe.
Cardiovascular disease. Heart abnormalities may result in collapsing or fainting episodes, which may look similar to an animal that collapses due to severe anemia. Additionally, heart disease can cause secondary lung problems, which may result in an elevated respiratory rate. Heart disease may also cause poor circulation, which can result in pale gums, making the animal appear anemic.
Seizures or other neurologic disease. Episodes of collapse may be difficult to differentiate from a seizure.
A thorough history and physical exam are important in order to establish a diagnostic plan. Because there are so many causes of anemia, historical and physical clues are important to narrow down the possible diagnoses. The length of illness may allow estimation of how long the anemia has been present. Travel history, exposure to ticks, current or recent medications, vaccine history, and past medical problems may provide important information. Evaluation of the mucous membranes (gums, anus, vulva or penis) will often reveal pallor, which is suggestive of anemia. Abdominal distension and intra-abdominal fluid can often be palpated by an experienced clinician, which may lead to a diagnosis of blood loss into the abdomen. An enlarged spleen may be present with various types of anemia, and this can often be palpated as well.
Additionally, careful examination for evidence of bruising or bleeding into the gut, eyes, nose, mouth, and ears can all be evaluated by the veterinarian. Yellow discoloration of the membranes or skin can be a marker of red blood cell destruction. This occurs due to rapid production of pigments that are a normal by-product of red blood cells. When cells are rapidly destroyed, the body becomes overwhelmed and the pigment (bilirubin) levels in the blood become elevated, imparting a yellow color to tissues.
Additional tests include:
Complete blood count. The CBC evaluates the red and white blood cells, as well as the platelets. The CBC will confirm the presence of anemia. The white blood cell and platelet counts are also very important, because some diseases affect multiple cell lines. If all counts are low, this may be an indication of disease within the bone marrow. A high white blood cell count may be seen with inflammatory disease, cancer, infectious disease and immune-mediated disease. If the platelet count is severely low, this may be a cause of blood loss. The CBC is also an important means of evaluating red blood cell morphology. Certain cancers and immune-mediated diseases may cause characteristic changes in the red blood cell shape.
Reticulocyte count. This is a measure of the number of immature red blood cells in circulation. This is a crucial test in evaluating an anemic animal, because it allows classification of the anemia. A normal bone marrow will respond to anemia by releasing immature red blood cells into circulation. This is called a regenerative anemia.
Regenerative anemia is caused by either blood loss or hemolyis (red cell destruction). Non-regenerative anemia is seen with either acute (very sudden) anemia of any cause, bone marrow disease, iron deficiency, or bone marrow suppression secondary to chronic disease or kidney failure. Performing a reticulocyte count is therefore very useful in narrowing down the causes of the anemia.
Biochemical profile. The biochemical profile provides important information with respect to overall organ function. For instance, it will aid in the diagnosis of chronic kidney failure, which is a common cause of anemia in older cats. It may also indicate abnormalities of the liver and endocrine organs.
Urinalysis. A urinalysis may reveal either blood in the urine or pigment changes, which are seen in cases of hemolytic anemia. It is important to interpret the urinalysis in light of the CBC and biochemical profile results. It also complements the biochemical profile in assessing kidney function.
Abdominal radiographs. Radiographs will provide good information with respect to organ size, and the presence of masses in the abdomen. Small masses may not be seen with routine radiographs. Fluid accumulation in the abdomen can also be noted on radiographs.
Abdominal ultrasound. Ultrasound often complements the findings on abdominal radiographs. It is a more sensitive means of examining the architecture of the abdominal organs, and pinpointing abnormal areas or masses. Ultrasound may also be useful to guide a fine needle aspirate of abnormal organs or to obtain any fluid present in the abdomen for analysis.
Thoracic radiographs. Radiographs of the thorax (chest) are important in cases where cancer is suspected, as the lungs are a common site of metastasis (spread of cancer) for many tumor types. Although metastatic disease can be present without showing up on the radiographs, the presence of metastasis in the lungs that is noted radiographically indicates that the disease has definitely spread to the lungs. Since all categories of anemia may be caused by cancer, thoracic radiographs are a common part of a work-up for anemia.
Coagulation profile. Tests of clotting function are imperative in animals with evidence of hemorrhage, either external or internal. Animals with hemolytic anemia are also prone to secondary bleeding disorders, so coagulation tests are useful for assessing most cases of regenerative anemia. Additionally, if the tests are abnormal, specific therapy may be indicated.
Bone marrow aspirate. This test is performed to obtain a sample of bone marrow cells for microscopic analysis. The bone marrow produces most of the red and white blood cells, as well as the platelets. Bone marrow evaluation is most useful in cases of non regenerative anemia, and in cases in which all cell lines are deficient. This test requires sedation or anesthesia for your pet, and is most commonly done at specialty hospitals.
Tests for infectious disease. Depending on the geographic location in which you live, certain infectious diseases may be likely to cause anemia. Infectious diseases implicated in causing anemia in dogs include babesiosis, ehrlichiosis, Rocky Mountain spotted fever, and sometimes heartworm. Additionally, certain fungal and protozoal infections can cause anemia as well.
Tests of immune function/dysfunction. A Coombs’ test looks for antibodies directed against red blood cells. This test can sometimes be used to confirm a diagnosis of immune-mediated hemolytic anemia, although a negative test result does not rule out the disease. An anti-nuclear antibody test also evaluates for the presence of antibodies aimed at one’s own cells and a positive test is another marker of immune-mediated disease.
Iron levels. If a patient has chronic blood loss, this can lead to iron deficiency. Iron deficiency is often suspected based on specific abnormalities seen in the CBC. Iron is important in the production of red blood cells, so iron deficiency will eventually cause a non-regenerative anemia. Various tests of iron stores can be evaluated if iron deficiency is suspected.
Genetic testing. There are rare genetic disorders documented in several breeds of dog that result in increased fragility of red blood cells, and can cause hemolytic anemia. In these cases, special genetic tests can be done to identify the abnormality. The breeds with known red blood cell defects include the English springer spaniel, West Highland white terrier, cocker spaniel, beagle, Alaskan malamute, and basenji.
Blood type. A blood type is not important as a diagnostic tool, but is important information for patients requiring a blood transfusion. Similar to blood types in humans, the type allows the veterinarian to choose the appropriate blood donor so as to avoid an adverse reaction to the transfusion.
Discussing specific therapies for the multiple causes of anemia is beyond the scope of this article. Articles on individual diseases should be referenced for more information. However, treatment in general may include the following:
Treating the underlying disease is the most efficacious way to resolve the anemia. This may consist of antibiotic therapy for some of the infectious diseases.
Suppression of the immune system is indicated for immune-mediated disease.
Removal of ingested toxins, like ingested pennies which contain zinc, whenever possible.
Avoidance of drugs is crucial in cases of suspected drug reactions.
Surgery and/or chemotherapy may be indicated to treat cancer.
Vitamin K therapy is a specific treatment for rat poison intoxication.
Iron supplementation is indicated in cases of iron deficiency.
Severe anemia caused by kidney failure can be treated with hormonal therapy.
Supportive care often consists of whole blood, or red blood cell transfusions in cases of severe anemia. Transfusions must be given at hospitals where close monitoring is available and there is access to an animal blood bank. Alternatively, there is a synthetic product that is available as a blood substitute. This is used in situations where blood is not readily available, or is not compatible with the patient’s blood.
Follow-up Care for Dogs with Anemia
Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your pet does not rapidly improve.
Administer all prescribed medications as directed. Alert your veterinarian if you are experiencing problems treating your pet.
Follow-up diagnostics will vary depending on the specific disease being treated. In most cases, pets need to be carefully monitored following a diagnosis of severe anemia. Your pet will be discharged from the hospital once the red blood cell count is considered stable and the disease process involved is deemed to be under control. A recheck exam in one week, and then every two weeks for the first several months is often indicated.
Frequent monitoring of the CBC will be necessary. Follow-up radiographs and/or ultrasound exam is also sometimes indicated.
It is crucial to keep a close relationship with your veterinarian while your pet is being medicated. As drugs are tapered or discontinued, it is important to make sure the anemia has not recurred.
As an owner, you can learn to monitor your pet’s gums at home. With a little practice, you may be able to tell if your pet is becoming anemic, due to the pallor of the gums. Additionally, you will want to monitor your pet for signs similar to what was seen when the illness was originally diagnosed. Things to watch for include lethargy and weakness, an increased respiratory rate, exercise intolerance, change in urine color, and anorexia.