Anemia/Erythrocyte Disorders Laboratory Procedures 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→ RBC • 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. Hemorrhage Anemia - Continued • 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. 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. Female Tick Laying Eggs 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.