7 Equine Liver Disease Short PPT

• Equine Liver Disease is a complex condition requiring careful consideration.

Hepatic Disease

• The liver is highly regenerative.
• Hepatic disease may be present without clinical signs.
• It is possible to have hepatic disease with clinical signs, but without liver failure.
• Hepatic failure is the most severe form of liver disease.

Clinical Signs of Hepatic Disease

• Initially, clinical signs are non-specific, including anorexia, depression, fever, colic, and weight loss.
• Later signs may include icterus or jaundice, indicated by hyperbilirubinemia.
• There are 3 reasons for hyperbilirubinemia: anorexia, hemolysis, and liver disease.
• Anorexia and hemolysis cause an increase in unconjugated or indirect bilirubin.
• Liver disease causes an increase in just unconjugated bilirubin.
• Post-hepatic disease is indicated by an increase in both, with direct bilirubin > 30% of total.
• Hepatic disease clinical signs also include photosensitization, which is a sign of liver failure and related to phylloerythrin.
• Further clinical signs can include hepatic encephalopathy, depression, head pressing, aimless walking, and yawning.
• Progression of hepatic encephalopathy may involve aggressive behavior, stupor, recumbency, unconsciousness, seizures (not always), and coma.

Treatment of Liver Disease

• Treatment is generally supportive.
• Specific treatments include antibiotics for bacterial cholangiohepatitis.
• Antibiotics are often used as a differential diagnosis.
• Fluid therapy is not needed for mild disease, but is often needed for moderate/severe cases, especially in the presence of hepatic encephalopathy.
• It is important to monitor electrolyte and acid-base balances, and watch for hypoglycemia.
• Anti-inflammatory drugs can be included in treatment.
• NSAIDs, DMSO, Pentoxifylline and Steroids are all options, with associated pros and cons.
• Nutritional support is important, with small frequent feedings of easily digested carbohydrates and a low protein diet.
• The goal is to lower glycogen stores, prevent lipolysis and subsequent hyperlipemia.
• Drugs such as Pentoxifylline and Colchicine may be used to inhibit fibrosis.
• Treatment for hepatic encephalopathy aims to reduce ammonia/toxin formation in the gastrointestinal tract.
• Mineral oil and Neomycin/Lactulose may be used, but diarrhea is a concern.

Equine Hyperlipemia/Hypertriglyceridemia

• Hyperlipidemia/Hypertriglyceridemia is defined by an increase in triglycerides (TG).
• A horse is not lipemic if TG < 500 mg/dl.
• There is also no organ failure
• It is common in all horses with systemic disease and negative energy balance.
• Hyperlipemia is defined as increased TG, > 500 mg/dl and opaque plasma.
• It is also associated with fat infiltration and organ dysfunction, especially in the liver.
• Severe hypertriglyceridemia can occur in normal-sized horses with triglyceride concentrations > 500 mg/dl, but the plasma is not opaque and there is no fat infiltration into the liver/kidney.
• Hyperlipemia is more common in minis, ponies, and donkeys, and affects females more often (pregnant, lactation), and is usually associated with overweight animals.
• Clinical signs include non-specific signs of anorexia and weakness.
• Signs of hepatic lipidosis include colic, hepatic encephalopathy, abortion, and renal failure.
• Hormone-sensitive lipase breaks down TG into FFA & glycerol.
• The body either uses oxidation for energy Acetyl CoA or ketones (poor to little).
• TG becomes VLDL, then lipoprotein lipase then FFA for peripheral tissues to use for energy.
• In hyperlipemia, there is an increase in release of VLDL, faster than peripheral tissues can use.
• Excess accumulation of TG in liver, not due to reduced ability to clear VLDL.
• Lipoprotein lipase at maximal activity.
• Overproduction of TG & VLDL.
• Hyperlipemia should be suspected in any mini/pony that is off feed.
• Measure triglycerides.

Hyperlipemia Treatment Aims

• Increase caloric intake by offering palatable feeds like green grass, alfalfa, and grain.
• Assisted Enteral Feeding via Water Soaked Pellets-large NG tube
• Commercial Formulas
• Intravenous or Parenteral Nutrition can also assist with increased caloric intake.
• Partial nutrition involves 5% Dextrose with IV fluids.
• Complete nutrition involves Concentrated dextrose and AA, but is more complicated.
• The main goal is to reverse negative energy balance, which may involve weaning early.
• Consider terminating pregnancy and identify & treat the underlying disease.
• Decrease Fat Mobilization, by using Insulin, as it has antagonistic effects on hormone sensitive lipase.
• Use insulin with dextrose, but monitor for hypoglycemia.
• Increase TG uptake into peripheral tissues by administering Heparin, as it will increase lipoprotein lipase, but activity is already increased.

Theiler's Disease

• Theiler's Disease is characterized by acute hepatic necrosis, serum-associated hepatitis, and serum sickness.
• Biological products such as tetanus antitoxin most common is know to cause liver necrosis.
• Takes weeks to months to develop
• Any antitoxin, plasma products, modified live vaccines can also have this response
• A 2018 publication linked Equine parvovirus-hepatitis, resulting in contamination of these products.
• The virus can also be found in normal horses and has evidence of horizontal transmission.

Tyzzer's Disease

• It is caused by Clostridium piliformis.
• Affects foals aged 7-42 days.
• Suspect this disease with foals with liver disease.
• Diagnosis is confirmed through histopathology, silver stain, PCR ans Culture, however is difficult to grow.
• The source is unknown Feces of healthy horses , possibly the Mare’s.
• Foals ingest feces via Corpophagia (normal).
• Rx- penicillin (and others)
• The Prognosis is poor.

Bacterial Infections

• Bacterial cholangiohepatitis is the most common bacterial infection of the liver.
• In most cases it is an ascending infection of bile duct that is 2ndary to other diseases like Enteritis and Cholelithasis.
• Primary hepatitis is uncommon.
• Diagnosed via Liver Biopsy, Culture & Histopath.
• Treatment includes antibiotics based on bacterial sensitivity.
• Common first use antibiotics include SMZ-TMP and Enrofloxaxin/B-lactam.

Hepatotoxins

• Diagnosis depends biopsy/histopath .
• Chronic Megalocytic Hepatopathy occurs, resulting in fibrosis and cells cant divide.
• Diagnosis can be made via histology.
• Pyrrolizidine alkaloid is the most common cause of chronic liver disease.
• Results from chronic low-level ingestion.
• Clinical signs present 4-12 weeks post ingestion.
• Liver disease & failure (HE) and Poor prognosis.

Cholelithiasis

• Cholelithiasis presents clinically as fever, colic and Icterus.
• Bloodwork results: Bile Acids show Marked increase
• Albumin and BUN is normal
• Direct Bilirubin will be > 30% of total.
• Treatment is long term medical management.
• Antibiotics, NSAID, DMSO are options.
• Surgery reported- difficult
• Prognosis depends on size & number of choleliths.
• Ursodiol or Ursodeoxycholic Acid is Naturally occurring bile salt that’s used to dissolve cholesterol stones
• Was previously contraindicated in horses, but Recent work shows this can actually be helpful