Diagnosis
A complete blood count may reveal mild non- regenerative anemia and variable leukocytosis. In one study, 33 % of the cats with lymphocytic CCH had leukocytosis, a lower percentage than for cats with neutrophilic CCH (Marolf et al.
2012). Cats with neutrophilic CCH tend to show neutrophilia with a left shift and/or toxic neutrophils, while cats with lymphocytic CHH may have lymphocytosis (Weiss, Armstrong, and Gagne 1997). Other laboratory findings seen in all types of CCH include elevated serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyltransferase (GGT), alkaline phosphatase (ALP) and hyperbilirubinemia. Many cats may show liver enzyme activities within reference range (Twedt et al. 2014). Hyperglobulinemia is sometimes seen in cases with lymphocytic CCH (Center 2009). Fasting and postprandial bile acids are often increased (Weiss et al. 1997). Coagulation tests may also be abnormal (Zoran 2012).Most cats with CCH often have a normal ultrasound examination, including liver size, echogenicity and biliary systems (Marolf et al. 2012). When abnormalities were present, they included hepatomegaly, hyperechogenic appearance of the liver, dilated common bile duct, and echogenic gall bladder contents. Ultrasound changes in the liver and biliary system are similar for both neutrophilic CCH and lymphocytic CCH, but lymphocytic CCH cats are less likely to have concurrent pancreatic changes detected ultrasonographically (Marolf et al. 2012).
Definitive diagnosis of neutrophilic CCH requires a liver biopsy or biliary cytology and positive culture, obtained via a percutaneous ultrasound-guided gallbladder aspirate. If suppurative inflammation and bacteria are observed on bile cytology, a diagnosis of neutrophilic CCH can be confirmed (Twedt et al. 2014). Enteric bacteria, most often Escherichia coli, but also other species such as Enterococcus sp., Bacteroides sp., Clostridia sp., Staphylococcus and α-hemolytic Streptococcus sp. may be cultured from the bile or liver of cats with acute neutrophilic CCH.
Most reported organisms are aerobic, but anaerobic organisms may also be found, therefore both aerobic and anaerobic cultures should be requested. Unfortunately, the rate of positive bile cultures tends to be low in neutrophilic CCH, even in untreated cats (Twedt et al. 2014). Using a florescence in situ hybridization (FISH) assay, a recent study observed intrahepatic bacteria in 33 % of cats with inflammatory liver disease examined (Twedt et al. 2013).Cytologic examination of fine-needle aspirates from the liver showing neutrophilic or lymphoplasmacytic inflammation may help support the diagnosis. However, liver aspiration cytology has a poor correlation with histopathology, especially in inflammatory liver disease (Twedt et al. 2014). Fine-needle aspirates of cats with CCH may also reveal marked hepatocellular vacuolation if secondary hepatic lipidosis is present (Zoran 2012).
Definitive diagnosis of any form of CCH requires a liver biopsy with histopathology and identification of the cellular infiltrate (neutrophilic, mixed, or lymphocytic). Additional changes described with neutrophilic CCH include periportal hepatocellular necrosis and bile duct dilation and proliferation, while additional changes in lymphocytic CCH include periductal fibrosis, diminished bile duct number, and sclerosing cholangitis (Center 2009). In some cases, it may be difficult to differentiate lymphocytic CCH from lymphoma - in these cases additional diagnostic tests including polymerase chain reaction for T-cell receptor gene rearrangement may be helpful (Center 2009). Techniques for liver biopsy include ultrasound-guided needle biopsy and wedge biopsy via laparoscopy or laparotomy. The latter two techniques have the advantage that it allows examination of the extrahepatic bile system, pancreas, and other intraabdominal structures (Twedt et al. 2014).