Cholangiohepatitis (Proceedings)

Classification of feline inflammatory liver disease(s)

Inflammatory disease has been reported to be the second most common category of liver disease in cats in the US (after hepatic lipidosis). However, within this category, there are a number of different pathologic patterns that may represent different stages of disease or even potentially separate disease conditions. This has resulted in considerable confusion about whether these various conditions should be lumped together in a broad category (cholangitis), or whether subtypes of inflammatory disease could be separated out to provide more specific and individualized information about etiology, diagnostic testing, therapeutic options, and prognosis.

Recently, the World Small Animal Veterinary Association (WSAVA) sponsored an international group of pathologists and clinicians tasked with standardizing histopathologic classification of liver disease in small animals. Among the recommendations of the WSAVA Liver Standardization Group (LSG) was that the term cholangitis be used in preference to cholangiohepatitis in cats. This recommendation was made because although inflammatory changes may occasionally extend into the hepatic parenchyma, the primary inflammatory changes are typically centered around the bile ducts. This is in contrast to dogs, in which the primary inflammatory liver disease, chronic hepatitis, directly involves the parenchyma.

Under the category of cholangitis, The WSAVA LSG recognizes three distinct forms: neutrophilic, lymphocytic, and fluke-associated. Of course, in clinical practice it can't be quite that simple. Although there are now criteria for separating these three categories based on histopathology, there is significant overlap in the clinical presentation and results from common clinical tests. There is also a further division of the neutrophilic form into acute and chronic forms (thought to represent different ends of a spectrum or progression of a single disease). Finally, there is a separate entity called lymphocytic portal hepatitis which has unknown clinical significance. Even though this scheme is not as simple as we might wish, it is still an improvement over the old system of just calling everything cholangiohepatitis. A roughly outlined comparison of the subcategories of cholangitis is presented in Table 1.

Table 1. Characteristics of different forms of feline cholangitis

Neutrophilic cholangitis

This is the most common of the feline inflammatory liver diseases and the most common biliary tract disease in cats. As the name implies, there is significant neutrophilic inflammation centered on the bile ducts.

In the acute form, the inflammation is exclusively neutrophilic and the inflammation is seen within the walls and lumen of the bile ducts and surrounding the portal areas. Degeneration and necrosis of the bile duct epithelium and extension of neutrophils through the limiting plate into the peri-portal hepatic parenchyma may also be seen in some cases.

In the chronic form, which is thought to represent a progression from the acute form, the inflammatory response includes variable numbers of neutrophils, lymphocytes and plasma cells. Inflammation is still centered on the bile ducts and changes to bile duct epithelium and extension of inflammation to the parenchyma may be seen in some cases. More commonly, however, there is evidence of bile duct epithelial proliferation/hyperplasia in these cases. Peri-ductal or bridging fibrosis may also be seen in some of these cases.

Both types of neutrophilic cholangitis are thought to result from bacterial infection of the biliary tract, although in the chronic form this may be additional self-perpetuating mechanisms responsible for the inflammation. Many cats with neutrophilic cholangitis also have concurrent diseases such as inflammatory bowel disease or pancreatitis, or secondary problems such as hepatic lipidosis.

Lymphocytic cholangitis

This condition is characterized by moderate to marked infiltration of small lymphocytes in portal areas, centered on and often extending into the walls of the bile ducts. Other changes such as biliary epithelial proliferation, bile duct dilation, or obliteration of bile ducts, or portal fibrosis may also be found.

This condition is recognized more commonly in Europe than in the US (although the reason for this is not understood). This is considered to be a very chronic condition which typically progresses over a period of months or years. The etiology is unknown, but is postulated by some to have an immune-mediated basis, while others have suggested a bacterial infections component.

Liver fluke associated cholangitis

Liver fluke infestations cause variable degree and type of inflammation of the bile ducts and commonly also cause marked thickening and cystic dilation of the bile ducts as well as periductal or portal fibrosis. Definitive diagnosis in made by identification of eggs or flukes.

Lymphocytic portal hepatitis

This condition is characterized by mild lymphocytic infiltration, as well as small numbers of neutrophils and plasma cells, limited to the portal areas and without evidence of bile duct involvement. The clinical significance of these changes in unknown at this time and it is thought to most likely represent a normal aging change, a non-specific repose to extra-hepatic disease, or a subclinical form of a specific liver disease.

Clinical Features of cholangitis in cats

A simplified comparative summary of the different forms of feline cholangitis is presented in Table1. In the majority of cases, diagnostic recommendations will include evaluating a serum chemistry, CBC, and urinalysis. Evaluation of liver function is also recommended (most commonly utilizing serum bile acids testing). Fecal examination(for fluke eggs) should also be performed if this is a reasonable differential for the patient's problem. Abdominal radiographs and ultrasound may also provide additional supportive evidence for the diagnosis or help to rule out other differential diagnoses, especially when combined with ultrasound guided fine needle aspiration and/or ultrasound guided percutaneous cholecystocentesis to collect samples for cytology and culture. As noted above definitive diagnosis requires biopsy and culture (or identification of flukes/fluke eggs).