Anemia in Dogs

What Is Anemia in Dogs?

Anemia is a common clinical problem that shows a decrease in red blood cells (RBCs). RBCs are produced in the bone marrow and carry oxygen to all tissues in the body.

Dogs show signs of anemia in various ways, based on its cause, severity, and duration. As anemia worsens, dogs show clinical signs of shock and failing cardiovascular and respiratory systems.

Anemia can be severe and life-threatening. Seek veterinary care immediately if your pet has pale gums, is struggling to breathe, is actively bleeding, or has unusual bruising.

In general, there are three ways that a dog can be anemic:

RBC loss: The bone marrow produces normal amounts of RBCs, but they are lost or leak outside the blood vessels.
RBC destruction: The body destroys the RBCs too soon.
RBC decreased production: The bone marrow does not make enough RBCs.

In addition to these general types, anemia may be described by how responsive the bone marrow is.

In regenerative anemia, the bone marrow correctly responds to the decreased RBC count and starts making new RBCs.
In nonregenerative anemia, the bone marrow does not produce enough RBCs.

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Symptoms of Anemia in Dogs

Clinical signs of anemia in dogs vary based on cause, severity, and length of disease. Dogs with chronic conditions may have vague, or no clinical signs until the anemia becomes severe. These dogs can acclimate to lower RBC counts over a longer period, whereas a dog with an acute blood loss may immediately show signs of distress and illness. Common signs of anemia in dogs include:

Weakness
Lethargy
Decreased appetite
Pica (eating non-food items)
Weight loss
Pale mucous membranes (gums)
Increased heart rate
Increased respiratory (breathing) rate
Difficulty breathing
Collapse
Small or large bruising over the body (petechiae and ecchymoses)
Jaundice (buildup of yellow coloring in blood and tissue)
Blood loss from nose, mouth, or urogenital or gastrointestinal systems

Causes of Anemia in Dogs

Anemia occurs in all breeds, ages, and genders of dogs. Some breeds are predisposed to a certain type of anemia, called Immune-mediated Hemolytic Anemia (IMHA) including:

Blood loss, when acute, occurs secondary to trauma, surgery, coagulopathies (poor clotting), rodenticide toxicity, a ruptured spleen, and bleeding cancers (hemangiosarcoma). Chronic blood loss can also lead to anemia in cases of long-term gastrointestinal ulcers, parasites (hookworms and fleas), tumors, lack of nutrition, and some drugs.

RBC destruction occurs when normal RBCs are removed from the system inappropriately and too early. Normally, RBCs last around 110 to 115 days in dogs and are removed by the spleen, liver, or bone marrow when they are old.

Common examples of this type of anemia are:

IMHA occurs when the immune system attacks the red blood cells. This can happen secondary to a trigger, such as some drugs, infections, cancers, or inflammatory diseases. It can also occur with no clear cause.
RBC parasites, such as babesia, can induce anemia.
Oxidative stress causes anemia and occurs in onion/garlic toxicities, acetaminophen and benzocaine toxicities, and zinc toxicosis, for example. Oxidative stress causes the normal oxygen-carrying hemoglobin to change to methemoglobin, which cannot bind or deliver oxygen to cells.
Mechanical damage can occur to RBCs in heartworm disease, vasculitis, cardiac disease, liver disease, disseminated intravascular coagulation (DIC), and in some cancers.
Other causes of RBC destruction include some infections, incompatible blood transfusions, genetic RBC abnormalities and disorders, diabetic ketoacidosis, propofol administration, and hypophosphatemia (low phosphorus).

Decreased RBC production occurs when the bone marrow does not make enough RBCs. This type is, inherently, nonregenerative. The following can all affect the body’s ability to produce RBCs:

Chronic inflammatory diseases
Chronic kidney disease
Hypothyroidism
Addison’s disease
Immune conditions
Infection
Cancer
Bone marrow suppression via infectious agents, drugs, and toxicities such as:
- Infectious agents—Parvovirus, babesia, ehrlichia
- Drugs—Chemotherapy agents, lead, methimazole, phenobarbital, fenbendazole, TMS, albendazole

How Veterinarians Diagnose Anemia in Dogs

Often, veterinarians may suspect anemia based on a patient’s history and clinical exam findings—especially if the dog has pale gums, bruising, or obvious abdominal tumors. However, anemia is only diagnosed by performing bloodwork to assess the RBC count as well other RBC factors such as size, shape, and color, which may help find the severity, chronicity, or cause of the anemia.

Complete blood count (CBC): This test looks at multiple RBC factors. These all help the veterinarian to chart the best plan of treatment for anemia.
PCV/TS: This is a relatively easy and quick diagnostic tool to look at the packed cell volume, which is another way to monitor the RBCs.
Reticulocyte count: This test looks for increased numbers of young RBCs, showing a regenerative response.
Biochemistry and urinalysis: These tests will look at organ function and other parameters that may be causing the anemia.
Slide agglutination test: This simple blood test looks for abnormal clumping of RBCs in IMHA.
Cytology or blood smear: This test evaluates RBCs under a microscope and may help find the cause and the bone marrow’s response.
Bone marrow evaluation: This test can help look for causes of anemia by examining the bone marrow for cancer, signs of regeneration, or infectious agents.
Imaging: Radiographs and ultrasound may help look for underlying causes of anemia, such as bleeding tumors.
Other tests: Serology for infectious agents, fecal tests, coagulation profiles, endocrine testing, organ function tests, and biopsy of tumors are all other possible tests for dogs with anemia.

Treatment of Anemia in Dogs

The primary goal for dogs with anemia is to treat the underlying condition. Treatment varies based on chronicity and severity of the disease. Some common treatment methods for anemia include:

Surgery to remove bleeding masses or repair traumatic wounds
Vitamin K therapy to treat rodenticide poisoning
Antiparasitic drugs to treat internal parasites
Antibiotics to treat tick-borne or other infectious agents
Discontinuing offending drugs
Steroids or immunosuppressing medications to treat autoimmune diseases
Blood products to provide RBCs and other important blood cells
Supportive care, including intravenous fluids

Recovery and Management of Anemia in Dogs

Most veterinarians use serial complete blood count and/or PCV/TS testing to watch the dog’s response to treatment, in addition to watching any other diseases potentially causing the anemia. In general, if the underlying disease is treated, anemia may take multiple weeks for the dog to return to normal, but clinical improvement is usually noted within a few days.

These dogs may require life-long medical management and monitoring for recurrence. Some causes of anemia such as trauma, infectious agents, or parasites, may be cured. However, severe cases of anemia may be too progressed to treat, even with aggressive therapy.

Management varies based on the predisposing factor and may be lifelong. Dogs with IMHA are at risk for flare-ups. Care should be taken whenever administering medications or vaccines in those dogs to decrease the risk of a recurrence.