Today's Veterinary Practice

JAN-FEB 2016

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

Issue link: http://todaysveterinarypractice.epubxp.com/i/619503

Contents of this Issue

Navigation

Page 66 of 139

tvpjournal.com | January/February 2016 | Today's VeTerinary PracTice aHs HearTWorM HoTLine Peer reviewed 65 cause this clinical fnding (Figure 2). other clinical fndings include: • Proteinuria, bilirubinuria, and hemoglobinuria (usually measured as hemolyzed blood) • sediment casts that indicate tubular disease and may occasionally reveal the presence of microfilaria. Heartworm Test Pets with cs typically have a heavy heartworm burden; therefore, infection confrmation is not usually diffcult. 2,3,8 as previously noted, microflaria may be found during evaluation of urine sediment, but more commonly, specifc testing is required: • direct evaluation of a single drop of blood may reveal microfilaria • Heartworm antigen test results are usually interpreted as "positive." if test results are negative, but history and clinical fndings suggest the possibility of cs, additional steps must always be taken to defnitively confrm or rule out this disease (see When Tests Say No but Other Findings Say Yes ). Cardiac Ultrasonography cs is confrmed by ultrasonography when a mass of adult heartworms is identifed within the right atrium, ventricle, and tricuspid orifce. Because the cuticular wall of the adult worm is refective, it can be easily visualized as parallel, hyperechoic lines (Figure 3 , page 66); a mass or tangle of worms is represented as numerous short, white, parallel lines (Figure 4 , page 66) and, when observed, confrms the diagnosis. i intentionally use the term cardiac ultrasonography rather than echocardiography because: 1. a c omplete assessment of the heart is not necessary; rather, the practitioner simply needs to identify the presence of adult heartworms in the right side of the heart to confrm cs Table. Caval Syndrome: Clinical Findings • Easily visualized bounding jugular pulse • Jugular distension • Lethargy and weakness • Mild icterus • Mild to severe ascites • Mild to severe hepatomegaly and/or splenomegaly • Mild to severe respiratory distress • Normal or harsh lung sounds, with crackles sometimes noted • Pale mucous membranes with delayed capillary refll time • Pronounced tricuspid murmur • Tachycardia • Weak peripheral pulses When Tests Say No but Other Findings Say Yes Interestingly, I have diagnosed pets with CS when both microflaria and antigen tests have yielded "negative" results. This can be confounding when history and clinical fndings make CS the most likely diagnosis. It also seems counterintuitive given the presence of a high population of mature adult worms typically composed of both sexes. However, even in heavily infected animals, "negative" test results do not confrm the absence of heartworms. They simply indicate that: • Microfilaria numbers are below detectable limits • No adult heartworm antigen is detected. Much has been written about possible reasons for "false-negative" results in heartworm-infected pets, but no specifc explanation has been given for such fndings in dogs with CS. Nonetheless, in my opinion, it makes sense that the role of the immune system and production of antibodies to various stages of heartworms can result in the arrested production or elimination of circulating microflaria, and formation of antibody complexes with adult worm antigen, rendering them unavailable for detection by routine tests. W h e FIGURe 2. Hemoglobinuria depicted as a dark red to black, coffee-colored urine (A); urine can be collected via cystocentesis (B). This fnding is often considered pathognomonic for CS. Courtesy Merial a b

Articles in this issue

Links on this page

Archives of this issue

view archives of Today's Veterinary Practice - JAN-FEB 2016