AETIOPATHOGENESIS AND DIAGNOSIS OF FELINE HEPATIC DISEASE

Jane began this webinar by comparing some aspects of liver disease in dogs and cats. In dogs, steroid hepatopathy is common both with Cushing’s syndrome and with iatrogenic causes, whereas in the cat steroid hepatopathy does not occur.  Asymmetric deposition of fat occurs in dogs that are obese but does not make them sick. Hepatic lipidosis in cats is common and is associated with anorexia of any cause. Chronic hepatitis is common in dogs and rare in cats.  In dogs it may progress to hepatic fibrosis leading to portal hypertension and a slowly developing ascites representing end stage disease. Ascites in cats is virtually never associated with hepatic fibrosis.

Continuing the comparison. Cholangitis is uncommon in dogs, and common in cats where it can be neutrophilic (bacterial) or lymphocytic (steroid responsive). Gall bladder mucocoeles are recognised in the dog but are very rare in the cat. Congenital portovascular shunts are much more likely to be recognised in dogs than cats. In both cats and dogs hepatic lymphoma is common and both species are susceptible to hepatocellular carcinoma although in the dog it tends to be focal and low grade making it amenable to surgical treatment. In the cat it is more diffuse and often associated with hepatic cysts and is more aggressive.

In summary when it comes to liver disease the cat is, as the saying goes, ‘not a small dog’.

As far as the incidence of types of feline liver disease is concerned statistics compiled over a 10 year period at the University of Minnesota indicate that hepatic lipidosis is the most common problem followed by cholangitis. The webinar concentrated in great detail on these two conditions.

Obese cats are at risk from hepatic lipidosis in particular, but with all cats it is important to maintain food intake in those that become anorexic for more than a few days. In experimental cats there was evidence histopathologically of hepatic lipidosis within 2 weeks of fasting. In clinical cases however this can be much quicker, between 2 and 7 days –although in most cases 4-7 days.

Precipitating causes of anorexia include cholangitis, pancreatitis, which is quite common but represents a challenging diagnosis, irritable bowel syndrome, neoplasia and others. Healthy cats can develop lipidosis if on an overly aggressive weight loss programme, or with a change to an unacceptable diet, unintentional food deprivation or stress,(boarding or travel for example.)

Clinically cats with hepatic lipidosis are typically bright and alert, unless unwell from an underlying disease. There is no age or sex predilection but as had been mentioned obese cats are at a higher risk.  Anorexia of several weeks duration is very suggestive, there may also be vomiting and diarrhoea, and the owner may have observed jaundice. On physical examination there is often hepatomegaly and other signs attributable to an underlying problem

The investigation of these cases includes a complete blood count and blood chemistries, ultrasonography, and measurement of feline pancreatic lipase.  Other tests might include blood ammonia, retroviral serology and serum bile acids) if the cat is not jaundiced.

Typical findings are hyperbilirubinemia, increased ALP (the most consistent) and increased ALT and AST (more variable).Fine needle aspirations and cytology also give valuable information and is far more commonly used due to the risk of haemorrhage from a biopsy.

A suggested treatment plan was:

  • Place a naso-oesophageal tube immediately (day 1)
  • Nutritional support. The cornerstone of therapy and adequate protein is the most important nutrient in reducing hepatic lipidosis. A calorifically dense diet high in protein and fat is optimum. Carbohydrates may be poorly tolerated.
  • Fluids and electrolytes
  • Appetite stimulants such as mirtazadine may be beneficial
  • Some authors recommend supplementation with micronutrients such as l-carnithine, taurine, and S-adenosylmethionine. There is no evidence currently for the benefits of these supplements. However there is some rationale for their use and this was dealt with, for each supplement, in considerable detail.
  • The success rate of therapy in milder cases is very high-in excess of 90% if the underlying problem is also dealt with.

The rest of this webinar dealt with Feline Cholangitis (Skinny yellow cats) and this can be divided into:

  • Neutrophilic Cholangitis (NC), which can be acute or chronic
  • Lymphocytic Cholangitis (LC)
  • Chronic cholangitis associated with fluke infestation in endemic areas

This classification excludes liver inflammation associated with systemic and infectious causes, such as FIP or toxoplasmosis. In feline cholangitis a liver biopsy is required for an accurate diagnosis. Cytology, useful in hepatic lipidosis, is not considered to be as beneficial as biopsy in cholangitis.

The disease is often associated with irritable bowel disease and pancreatitis. This combination is known as Feline Triaditis.  In a University of Minnesota study 83% of cats with cholangitis had concurrent pancreatitis.  In another study 60% of cholangitis cases had pancreatitis, 50% had concurrent IBD and 32% had both pancreatitis and IBD

The clinical signs of cholangitis include lethargy, anorexia, vomiting, weight loss and jaundice. Laboratory findings common to both types of cholangitis include:

  • Increased ALT, AST
  • Increased ALP/GGT
  • Increased bilirubin
  • Liver enzyme activity is a poor predictor of the degree of inflammation
  • With NC there may be an increased white cell count (55% NC versus 32% LC)
  • There may be abnormalities of the gall bladder noted on ultrasonography with triplication or other divisions in the gall bladder. Excellent ultrasound images demonstrating these abnormalities were shown

The treatment of NC is suggested to be: –

  • Supportive care to include fluids, nutritional support, vitamin K given intramuscularly or subcutaneously
  • Vitamin B12
  • Antibiotics for 4-6 weeks. Examples given were clavulanic potentiated amoxicillin, Marbofloxacin +/- metronidazole and cephalosporin
  • Ursodeoxycholic acid. This is likely to be of benefit although more evidence-based research is needed. The rationale for the use of this drug was explored in great detail.

Lymphocytic cholangitis presents most commonly in older cats.  There may be a breed predilection for Norwegian Forest cats and Persians. The disease is clinically silent during the early stages showing slow progression and usually chronically established by the time of biopsy. An immune mediated cause has been suspected but there is a variable response to steroids. Recently Helicobacter pylori have been found in 2 studies, mirroring the findings in human primary biliary cirrhosis and sclerosing cholangitis.  The significance of this has to be established.

LC cases are thin and jaundiced and definitive diagnosis rests on histopathological findings..LC treatment comprises:

  • Supportive treatment as for NC including fluids, nutrition
  • Initial treatment with antibiotics for 7-10 days
  • Prednisolone 1mg/kg for 2 weeks. This may be required long term after tapering the dose with the aim of keeping the bilirubin level in the reference range
  • Micronutrient support as for LC

Finally the key points of cholangitis were summarised as: –

  • Clinically NC and LC look very similar
  • NC likely to be associated with ascending bacteria
  • Aetiology of LC may be immune mediated? Biliary tracts may show bizarre dilatations on ultrasound
  • Prednisolone + Ursodeoxycholic acid is currently the medical treatment of choice
  • Serum bilirubin appears to be the best indicator for monitoring
  • Pancreatitis and IBD occur commonly with either form of cholangitis

The final part of this webinar demonstrated the placing of naso-oesophageal tubes (preferred to naso-gastric tubes as the latter risks reflux of acid from the stomach)

The placements were well illustrated.

Reviewer’ comments

The subject of feline liver disease gets a very thorough airing in these two (part 1 and part 2) veterinary webinars. Both general practitioners wanting to get up to speed on the subject and specialists, including those on the specialist route, will get an enormous amount from the material given.  Throughout, the relaxed style and clear explanation doesn’t falter and neither will your interest.

 

 

 

 

 

 

 

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