Anemia Defined: A condition of reduced oxygen carrying capacity of erythrocytes
Erythrocyte disorders May be associated with : Decreased production of RBC’s Increased destruction of RBC’s Inappropriate loss of RBC’s
Diagnosis A systemic, diagnostic approach to anemia is necessary and should include: Good history Physical exam CBC Blood film/slide analysis
Treatment Should be aimed at correcting the primary disorder and supporting the patient. IMPORTANT to establish whether the anemia is REGENERATIVE or NON-REGENERATIVE. Reticulocyte counts are used to evaluate if the anemia is regenerative or non-regenerative. WHY??? Remember that regenerative anemias are usually the result of hemorrhage or hemolysis and non-regenerative anemias may involve the bone marrow.
Treatment Continued Remember that regenerative anemias are usually the result of hemorrhage or hemolysis and non-regenerative anemias may involve the bone marrow. (Remember Myeloproliferative Disorders???)
Regenerative v. non-regenerative Regenerative Anemia: Increased reticulocytes, nRBC’s, anisocytosis, polychromasia and Howell-Jolly bodies. Indicates the bone marrow has responded to a demand for RBC’s by increasing production and releasing into circulation adequate numbers of immature RBC’s (aka polychromatophils)
Polychromatophils Bluish to reddish-blue cytoplasm Slightly larger than mature RBC’s (why?) When stained with New Methylene Blue = Reticulocytes
Erythrocyte Life Span Stem Cell → Rubriblast → Prorubricyte → Rubricyte → Metarubricyte → Reticulocyte → RBCStem Cell → Rubriblast → Prorubricyte → Rubricyte → Metarubricyte → Reticulocyte → RBC Metarubricyte- nucleated RBC released in severe anemia.Metarubricyte- nucleated RBC released in severe anemia.
Reticulocytes Remember these??? Irregular net-like structures in polychromatophils when stained with New Methylene Blue. These structures are called reticulum. Reticulum is irregular clumps of ribosomal RNA and organelles like mitochondria. Most species only have one form of reticulocyte. Which species has two NORMALLY?
Reticulocytes - continued Non-regenerative anemia Decreased production of erythrocytes caused by inadequate production of RBC’s by the bone marrow. Canine reticulocytes when stained with New Methylene Blue are AGGREGATE only. Will appear as hyperchromatocytes and as macrocytes in comparison with normocytes.
Feline Reticulocytes Punctate v. Aggregate The aggregate reticulocytes mature into the punctate form within 12 – 24 hours. Punctate reticulocytes circulate for ~7 – 10 days before all RNA is lost. Reticulocyte counts of feline blood should only include the percentage of aggregate reticulocytes as punctate reticulocytes are not counted since they don’t reflect the most recent bone marrow response. e.g. An anemic cat with only punctate reticulocytes is NOT actively regenerating RBC’s at this time, but has shown some bone marrow regneration in the last 7 – 10 days.
HemorRhage anemia Blood loss anemias are associated with acute, sub-acute and chronic hemorrhage. Hemorrhage – Defined as the escape of blood from a ruptured vessel. May be external or internal. Acute: Extremely sudden onset. Usually follows trauma or surgical procedures Sub-acute: Recent or rather sudden onset. May take hours-days for clinical signs to appear. Chronic: A continuous, constant loss of blood. Parasitism is most common cause of chronic anemias.
Most common cause of hemorrhage related anemia is trauma. Can also be caused by thrombocytopenia which is characterized by petechial hemorrhages on ear pinna(e), mucous membranes, and other non-haired areas like the abdomen. Treatment: Includes steroids, plasma or whole blood transfusions, and avoidance of trauma. Hemorrhage Anemia - Continued
Iron-deficiency anemia Iron is important in the body because it is the main constituent of hemoglobin. Caused by chronic external blood loss. Note: severe flea infestations, GI parasites, gastric ulcers and bleeding tumors can cause significant blood loss over time. The iron and hemoglobin lost with this external bleeding result in the formation of altered RBC’s and decreased life span. Treatment includes correcting the cause of the blood loss and iron supplements.
Hemolytic Anemia Defined: The increased destruction of erythrocytes. (aka, hemolysis) Caused by immune components attaching directly or indirectly to the RBC membrane, altering its structure. The body, attempting to regain homeostasis, begins to remove these altered cells. In cats, the most common cause of hemolytic anemia is Mycoplasma haemofelis, a blood born parasite. Feline Leukemia can also stimulate an immunohemolytic anemia. Treatment is aimed at suppressing the immune system w/ steroid therapy. In dogs, the most common cause is an underlying inflammatory process.
Blood-Borne Parasites Several commonly seen blood parasites can produce anemia through hemolysis. The parasite attaches to the erythrocyte membrane, causing an increased destruction of the cells. Animals having non-specific signs such as weight loss, anorexia, fever of unknown origin (FUO), hepatomegaly and splenomegaly should have blood films examined for the presence of blood parasites.
Toxin-induced anemia/Heinz body anemia Drugs can be a source of anemia in small animals. Hemoglobin will denature and form Heinz Bodies. Cats are considered to be more susceptible to Heinz body formation due to the structure of their hemoglobin. One of the most common Heinz body anemias seen in the dog is onion toxicity. Acetaminophen toxicity can cause anemia in cats and dogs.
Ehrilichiosis Ehrlichia is a rickettsial disease spread by the brown dog tick. First recognized in the US in 1963 and gained prominence because of the large losses among working military dogs stationed in Vietnam. Infection occurs when the organism is transported via the tick saliva during a blood meal. Infection is initially in WBC’s. Can be transmitted from infected animal to non-infected animal. Infected circulating cells can infect other organs and may result in platelet consumption and erythrocyte destruction.
Von Willebrand’s Disease Canine vWD is the most common inherited blood disorder. In healthy dogs, von Willebrand’s factor (vWF) promotes platelet clumping. Decreasing amounts of the factor causes a bleeding disorder. Has been identified in 54 breeds, with Doberman Pinschers, German Shepherds, and Labrador Retrievers being the most common. Dogs with this disorder should not be bred and special care must be taken at times of surgery to ensure hemostasis.