Veterinary Medicine - December 2008 - (Page 665)

1. A peripheral blood smear from an anemic dog reveals that the majority of the RBCs are small, dark, and lack central pallor, which indicates they are spherocytes. Several large polychromatophilic cells are also present, which indicate a regenerative response to the anemia (Wright’s-Giemsa stain; 1000x) 2. A peripheral blood smear from an anemic dog reveals that the RBCs are prominently clumped together, which indicates agglutination. A saline dispersion test should be performed for conﬁrmation. Additional ﬁndings in this smear include moderate polychromasia and rare nucleated RBCs, which indicate a regenerative response, small round cells lacking central pallor suggestive of spherocytes, and a neutrophilic leukocytosis, which indicates inﬂammation (Wright’s-Giemsa stain; 500x). Mycoplasmosis does not cause a clinically relevant anemia in dogs that have not undergone a splenectomy, but it can cause a mild to severe anemia in cats.1 A coagulation panel is justi ed to investigate blood loss as a cause of anemia or as an indicator of disseminated intravascular coagulation (DIC).24 Elevations in coagulation times, however, have not been shown to predict thromboembolism or mortality in patients with IMHA. In one study in dogs with IMHA, no statistical difference was noted in survival times in patients with or without baseline coagulation abnormalities.25 An antinuclear antibody (ANA) test is occasionally performed in patients with IMHA to investigate systemic lupus erythematosus; but to truly have this condition, patients must have high ANA titers and two or more manifestations of autoimmunity (e.g. dermatomyositis, vasculitis, polyarthropathy) in addition to IMHA.26 False positive results can occur with certain underlying infections and neoplastic diseases. A bone marrow aspirate or core biopsy may be helpful in an ongoing nonregenerative anemia to search for underlying diseases such as RBC aplasia or hypoplasia, immune destruction of RBC precursors, or neoplastic in ltration.24 on blood smears in patients with IMHA. As many as 89% of dogs with IMHA have spherocytes; however, dogs with secondary hemolysis from hypophosphatemia, zinc intoxication, or splenic disease can also have them in small numbers.1,14 Imaging Obtain abdominal radiographs to investigate triggers of hemolytic anemia, such as ingestion of zinc-containing foreign objects or abdominal neoplasia. If abdominal radiographs reveal suspicious ndings, an abdominal ultrasonographic examination is warranted. In middleaged to older dogs, it is recommended that routine thoracic radiographs also be obtained to investigate whether primary or metastatic neoplasia may be a cause of IMHA. Direct Coombs test The direct Coombs test, also called the direct antiglobulin test, can be used when IMHA is suspected but autoagglutination is not seen. This test is run on an EDTA blood sample and will identify antibodies or complement on a patient’s RBC surface. A positive result on a direct Coombs test does not distinguish between primary and secondary causes of IMHA.1 False positive results are seen in both dogs and cats and can be a result of concurrent diseases such as neoplasia, infections, in ammatory conditions, or recent drug administration.15 False negative results are also common and can occur in up to 42% of all dogs with IMHA.16 Thus, this test can be prone to errors and is not sensitive enough to detect low levels of clinically relevant antibodies.9 Flow cytometry also detects antierythrocyte antibodies and is more sensitive for detecting IgG than is the Coombs test, but it is not yet widely available to general practitioners.15,17 Other diagnostic tests A thorough search for underlying infection is warranted in cases of IMHA. Chronic infections, such as pyometra, abscesses, urinary tract infections, and discospondylitis, have all been associated with triggering IMHA.1 Transmissible causes of IMHA, such as infection with the hemoprotozoan Babesia gibsoni, are increasingly frequent in the United States.18 A recent study described a breed predisposition to B. gibsoni infection in American pit bull terriers.18 Studies have also described transmission associated with blood transfusions and dog bites.19-21 Other infectious organisms, such as Ehrlichia and Diro laria species, have also been associated with anemia in dogs.22,23 VETERINARY MEDICINE December 2008 665

Table of Contents Feed for the Digital Edition of Veterinary Medicine - December 2008

Veterinary Medicine - December 2008 Contents Letters Thanking Our Valued Reviewers Practical Matters Idea Exchange Why Do Dogs and Cats Eat Grass? Managing Atypical and Critical Cases of Primary Hypoadrenocorticism in Dogs Behaviors Suggestive of Postoperative Pain in Cats What to Consider When Considering Digital Radiography Avoid Common Bandaging Mistakes in Dogs and Cats IMHA: Diagnosing and Treating a Complex Disease CE Form/Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - December 2008

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