What is the liver?
The liver is the second largest organ in the body after the skin and is located just behind the diaphragm in dogs and cats. It plays many roles in digestion and metabolism including the removal of toxins and pathogens from the blood, taking up nutrients to make amino acids, and storage of dietary energy. The liver is able to use its stores to form glucose and fuel the body when needed.
Liver disease
There are four main types of liver diseases:
- Inflammatory diseases
Dogs are more likely to be diagnosed with chronic hepatitis or cirrhosis whereas cats are more commonly diagnosed with cholangiohepatitis, inflammation of the biliary tree often caused by bacterial infection.
- Storage disorders
Hepatic lipidosis is an acquired problem caused by accumulation of fats within the liver. This condition commonly occurs in cats after periods of fasting, or secondary to other diseases that may cause a cat to stop eating.
Dogs more often have copper storage hepatopathy, and accumulation of copper in the liver. This condition can develop due to a defect in copper metabolism or secondary to chronic liver disease.
- Circulatory diseases
Blood vessel disorders that interrupt nutrient supplies to the liver are more common in dogs but can occur in cats as well. Portosystemic shunts are an example of a circulatory disease that occurs when blood vessels that run from the digestive tract to the liver develop an abnormal route, causing the vessels to bypass the liver. Other examples include microvascular dysplasia and primary portal vein hypoplasia, which cause decreased blood flow to the liver.
- Liver tumours
Liver tumours occur in both dogs and cats and can be benign or cancerous. They can either originate from the liver or infiltrate the liver after spreading from another area of the body. Tumours arising from the liver are more likely to be benign than cancerous.
General symptoms of liver disease
- Decreased appetite
- Weight loss
- Vomiting and/or diarrhea
- Icterus/jaundice
- Fluid accumulation in the abdomen
- Fatty, glistening feces
- Hepatic encephalopathy
- This symptom is most often associated with portosystemic shunts. It occurs due to the liver’s inability to detoxify ammonia that accumulates from undigested proteins. High levels of ammonia are toxic to the nervous system, affecting brain function and causing symptoms such as head pressing, circling, weakness, and incoordination.
The liver can repair itself from most insults, which means liver damage may not be noticeable until 70% of functional capacity has been lost. Appropriate nutritional support is critical for liver regeneration while addressing the root cause of the liver disease.
Nutritional considerations
Energy
Adequate caloric intake is important to avoid the need to break down muscle mass to provide energy for the body.
Protein
To provide the body with the amino acids needed to help the liver recover, feed protein levels within normal recommended ranges. For dogs this is 20-25% on a dry matter basis. Cats have higher protein requirements and can have 30-40% on a dry matter basis. Protein sources that are easily digested and absorbed by the body are important to decrease the ammonia burden. Animal protein sources such as cooked eggs, meat, and fish are more likely to fulfill these criteria.
However, in cases of hepatic encephalopathy vegetable protein sources, specifically soybean meal, have been shown to be beneficial. If symptoms of hepatic encephalopathy continue, then protein intake may need to be restricted.
Fats
Dietary fats help to increase the palatability and caloric density of foods. Fat restriction is not necessary in cases of liver disease unless there is an obstruction inhibiting the release of bile from the liver affecting fat digestion.
Carbohydrates
Complex carbohydrates also help to increase the energy density of the diet and act as a non-protein source of Calories to help reduce the body’s need to use protein as an energy source. This is especially important in pets with hepatic encephalopathy as it helps to reduce the accumulation of ammonia in the body. Complex carbohydrates take longer to digest since they require more work for the body to breakdown before absorption and include starches, legumes, and whole grains. These types of carbohydrates help to avoid overwhelming the liver with lots of sugars.
Vitamins and Minerals
Antioxidants, such as vitamin E can help to protect the liver from inflammatory damage. Even though dogs and cats don’t have a dietary requirement for Vitamin C, providing extra can help to support the activity of vitamin E. Additionally, synthesis of taurine, an essential amino acid important for bile production, is often decreased in patients with liver disease. Supplementing with dietary taurine can help to maintain bile synthesis. Dietary zinc can be helpful in patients with copper hepatopathy to reduce copper absorption.
In cases of microvascular dysplasia and primary portal vein hypoplasia, sodium restriction is required to help control blood pressure and reduce the risk of fluid accumulation in the abdomen. Dietary vitamin K supplementation is recommended to decrease the risk of gastrointestinal ulceration often associated with these disorders.
Feeding Recommendations
Patients with liver disease benefit from multiple small meals spread out over the day. If the animal is not consuming enough food on their own, it may be beneficial to place a feeding tube to ensure the patient is consuming enough Calories.
If your pet is showing symptoms of liver disease and/or you are concerned about their appetite, body weight or body condition, consult your veterinarian.Energy
Adequate caloric intake is important to avoid the need to break down muscle mass to provide energy for the body.
Written by: Alison Ng, BScH, OVC Class of 2027
Reviewed by: Sarah K. Abood, DVM, PhD, Associate Professor, Nestlé Purina Professorship in Companion Animal Nutrition
References (1–5)
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