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Today's Ve T erinary Prac T ice | s eptember/ o ctober 2016 | tvpjournal.com TH e ye LL o W ca T: dia G nos T ic & TH era P e UT ic s T ra T e G ies Peer r eviewed 44 as hepatomegaly with hepatic lipidosis, cranial abdominal discomfort with pancreatitis, and tachycardia with anemia. The physical examination is often dominated by the color of the cat. Icterus is best appreciated as a discoloration of the mucous membranes, the sclera (Figure 3), and/or the inner aspect of the pinnae (Figure 4). The intensity and actual color may be influenced by the normal tissue color, degree of anemia, and perfusion. The clinical condition and color of the cat are influenced by both the degree of anemia—mild to severe—and the time course of r BC destruction— acute or chronic. Laboratory Analysis Changes on the serum biochemical profile are nonspecific. The degree of elevation in total bilirubin is cited as a nonspecific but generally guides to the most likely location or etiology of the problem: • 3 to 6 mg/dL is associated with prehepatic hemolysis, FIP, pancreatitis, and sepsis • Greater than 12 mg/dL is associated with hepatic lipidosis and EHBO. PREHEPATIC HYPERBILIRUBINEMIA DIAGNOSTICS Blood Analysis The laboratory diagnostic workup for the vast majority of icteric cats starts with determining whether prehepatic hemolysis is present. Complete Blood Count Hemolysis can often be an extravascular antibody- mediated process in which the serum turns icteric. A simple hematocrit tube can be expected to identify a significant degree of anemia and a relatively normal serum total protein. l ess frequently, the hemolysis occurs within the vasculature itself, in which case the serum may appear pink, while both the plasma (hemoglobinemia) and urine (hemoglobinuria) appear red. A complete blood count (CBC) more accurately and completely characterizes the anemia as regenerative or nonregenerative; however, the regenerative process may take up to 5 days to manifest as an appropriate increase in the absolute reticulocyte count (> 40,000–60,000/ mc l , depending on the laboratory). A CBC also identifies other potentially important erythrocyte characteristics. The degree of anemia is cited as a nonspecific but general indictor of the likelihood that feline icterus is the result of prehepatic hemolysis. As a rule of thumb, prehepatic hemolysis usually results in a packed cell volume (PCV) of less than 13% to 20%; however, the cat's baseline or normal PCV, hydration status, and the time frame over which the hemolysis occurred may all impact the clinical signs, measured PCV, and elevation in total bilirubin. Blood Smear Careful examination of the blood smear is a critical step in any attempt to identify infectious organisms or indicators of immune-mediated agglutination. Infectious Disease Infectious disease testing is commonly used for prehepatic hyperbilirubinemia (Table 2, page 42). Mycoplasmosis In addition to hyperbilirubinemia, cats with mycoplasmosis are frequently hyperglobulinemic as a Figure 3. The sclera of the feline immune- mediated hemolytic anemia patient. Figure 4. The pinna of the feline immune- mediated hemolytic anemia patient.