What causes a low hematocrit? Explore the various factors that can lead to anemia and decreased red blood cell count in dogs. Learn how to diagnose and address the underlying conditions through comprehensive medical tests and analysis.

Defining Anemia and Hematocrit

Anemia is a medical condition characterized by a reduced number of circulating red blood cells (RBCs), hemoglobin (Hb or Hgb), or both. It is not a specific disease but rather the result of an underlying condition or disease process. The hematocrit (HCT) or packed cell volume (PCV) is a measure of the percentage of red blood cells in the total blood volume. A normal dog has a hematocrit ranging from 35% to 55%.

Causes of Low Hematocrit

There are several potential causes of a low hematocrit, which can be grouped into three main categories:

Diseases Causing Blood Loss

The primary causes of blood loss in dogs include trauma or injury to blood vessels, internal organ damage, heavy infestations of blood-sucking parasites (e.g., fleas, ticks, hookworms), and tumors (benign or malignant) in the gastrointestinal tract, kidneys, urinary bladder, or spleen that can cause bleeding.

Diseases Causing Hemolysis

Hemolysis, or the breakdown and destruction of red blood cells, can be caused by autoimmune diseases (such as immune-mediated hemolytic anemia), blood parasites (e.g., Babesia), chemicals or toxins (e.g., zinc, rat poisons, onions, garlic), and certain types of cancer.

Diseases Decreasing Red Blood Cell Production

Conditions that suppress the bone marrow’s ability to produce new red blood cells can also lead to a low hematocrit. These include various types of cancer, infections, and chronic diseases that affect the body’s ability to manufacture sufficient RBCs.

Diagnosing Anemia and Low Hematocrit

To diagnose anemia and determine the underlying cause of a low hematocrit, veterinarians will typically perform a series of tests, including:

Complete Blood Count (CBC)

The packed cell volume (PCV) or hematocrit (HCT) is the most common test used to identify anemia. If the PCV is below 35%, the dog is generally considered anemic.

Reticulocyte Count

The presence of increased numbers of reticulocytes, immature red blood cells released prematurely from the bone marrow, indicates that the body is attempting to compensate for the anemia (a “responsive” anemia).

Blood Smear Examination

A careful study of the blood smear can reveal the presence of blood parasites, abnormal cells, or other signs that may point to the underlying cause of the anemia.

Biochemical Profiles and Urinalysis

These tests evaluate organ function and electrolyte levels, providing important information about the overall health of the dog and potential contributing factors to the anemia.

Imaging Studies

Radiographs (X-rays) or ultrasound may be recommended to help determine the cause of the anemia, such as the presence of tumors or internal bleeding.

Addressing the Underlying Cause

Once the specific cause of the low hematocrit has been identified, the veterinarian can develop an appropriate treatment plan. This may involve addressing the underlying condition, managing blood loss, or supporting the bone marrow’s production of red blood cells.

Treating Blood Loss

If the anemia is due to blood loss, the veterinarian will focus on identifying and addressing the source of the bleeding, such as repairing damaged blood vessels, removing tumors, or treating parasitic infestations.

Managing Hemolytic Anemia

For anemia caused by hemolysis, the treatment may involve immunosuppressive medications for autoimmune conditions, antiparasitic drugs for blood-borne parasites, or addressing the underlying cancer or toxin exposure.

Supporting Red Blood Cell Production

In cases where the bone marrow is not producing enough red blood cells, the veterinarian may prescribe medications or supplements to stimulate erythropoiesis (red blood cell production) or address any underlying conditions affecting the bone marrow.

By understanding the various causes of low hematocrit and following a comprehensive diagnostic approach, veterinarians can effectively identify and treat the underlying condition, restoring the dog’s red blood cell count and improving their overall health and well-being.