Today's Veterinary Practice

SEP-OCT 2016

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tvpjournal.com | September/October 2016 | T O day' S Ve T erinary Prac T ice TH e ye LLOW ca T: dia G n OST ic & TH era P e UT ic ST ra T e G ie S Peer r eviewed 45 result of chronic immune stimulation, and they may have mild to moderate elevations in liver enzyme activity as a result of anemic—hypoxia-induced hepatocyte necrosis. Feline Leukemia Virus There are a variety of technologies available to easily test for the Fe l V p27 antigen, which is present in the majority of infected cats. Cytauxzoonosis Biochemical changes with Cytauxzoon felis are nonspecific, while anemia, pancytopenia, and thrombocytopenia may be seen on the CBC. Immune-Mediated Disease Diagnosing IMHA using persistent r BC agglutination, a positive Coombs' test, r BC characteristics, and reticulocytosis can be challenging in cats; other potential causes of prehepatic hemolysis must be carefully considered. Agglutination can be difficult to distinguish from normal rouleaux formation in the cat, but true r BC autoagglutination can be identified by mixing one drop of potassium ethylenediaminetetraacetic acid (K-EDTA) whole blood with 1 to 4 drops of 0.9% sodium chloride on a microscope slide. Macroscopic slide erythrocyte agglutination is seen in all IMHA cats, although it rarely persists following r BC washing. Biochemical abnormalities are varied and inconsistent, although the majority of cats have a positive direct Coombs' test, further supporting the diagnosis of IMHA. However, Coombs' testing should be interpreted with caution and related to other clinical and hematologic findings. 12 Inherited Erythrocyte Disorders Biochemical and CBC parameters of cats with erythrocyte PK deficiency are nonspecific and inconsistent among patients, although hyperglobulinemia was frequently seen. Genetic testing and responsible breeding are clearly important considerations. HEPATIC HYPERBILIRUBINEMIA DIAGNOSTICS Laboratory Analysis Hepatic hyperbilirubinemia is caused by significant primary hepatic disease. A minimum diagnostic database includes a CBC, serum biochemical profile, urinalysis, and Fe l V/FIV status. Once the cat is icteric, and prehepatic causes have been ruled out, the serum bilirubin is elevated to the point where a bile acids test for liver function is redundant; the results will be abnormal. With mild hyperbilirubinemia (< 2 mg/d l ), a bile acids test may be warranted to assess liver function. Imaging Ultrasonographic imaging of the entire abdomen by a board-certified specialist is an essential step in the assessment of the feline hepatobiliary system. Ultrasound is a powerful tool for assessing the liver parenchyma, visualizing the biliary system, and searching for EHBO. Fine Needle Aspiration Ultrasound-guided fine needle aspiration (FNA) is also a minimally invasive technique for acquiring samples of certain tissue, such as the liver, pancreas, and lymph nodes, and masses for cytology and culture. Coagulation parameters and clotting times should be determined prior to FNA. Hepatic Lipidosis In cats that present with hepatic lipidosis, it is critical to put diagnostic effort into identifying the disease that led to the cat's anorexia in the first place, whether that is as simple as dental disease or as complex as feline pancreatitis. Failure to identify and address the concurrent condition is very likely to result in the cat being presented to the hospital again with the same complaint. Cholangitis The diagnostic effort of feline cholangitis is directed toward identification of the predominant inflammatory cell type present in the cat's hepatobiliary system: acute neutrophilic, chronic neutrophilic, or lymphocytic. FNA of the liver is a relatively simple procedure that may produce a cytologic sample suggestive of cholangitis, but this technique has significant limitations. It may be of low yield, resulting in a nondiagnostic sample, the nonspecific report of hepatocellular vacuolization, or an interpretation that would be different than that obtained by histopathology. 13 Technically more challenging techniques, best performed by board-certified specialists with ample experience, are ultrasound-guided cholecystocentesis and laparoscopy-assisted gallbladder aspiration. For both procedures, samples are collected for cytology

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