Hepatic problems

Liver function in brief

The liver is the largest metabolic organ in the canine body and has a number of different functions. The liver plays an essential role in the metabolism of proteins, minerals, fats, and vitamins. It stores glucose, vitamins, and iron, regulates blood sugar, and produces other necessary substances from glucose, such as certain amino and fatty acids. The liver also produces bile acid, a substance essential to digestion, particularly to the absorption of fats and fat-soluble vitamins. Another essential function of the liver is to remove waste products and various toxic substances from the body.

Blood flow to the liver differs from that of other organs. The hepatic artery brings oxygenated blood to the liver, but in addition to this, there is the portal vein, which delivers venous blood to the liver. Blood circulated in the intestinal capillaries goes directly to the liver via the hepatic portal vein before entering systemic circulation. It contains substances absorbed from the intestine as well as various waste products.  Liver cells, known as hepatocytes, are located at the edges of the capillaries. Hepatocytes are responsible for the production of various substances, playing a role in protein synthesis and the formation of bile, fat, and carbohydrates. Stellate macrophages (Kupffer cells) located on the walls of the sinusoids remove and neutralize toxins that have been ingested through food or produced by intestinal bacteria.

Liver disease in dogs

Although liver disease in dogs is not uncommon, the symptoms can be vague and can be easily confused with those of other diseases. Often, liver dysfunction in dogs is detected in a blood test showing elevated levels of liver enzymes. Common symptoms include:

• Weight loss, anorexia
• Excessive drinking and urination
• Gastrointestinal symptoms such as diarrhoea and vomiting
• Ascites
• Jaundice

Jaundice is a visible symptom of liver disease. It can be seen in the sclera of the eyes, on the mucous membranes, and in the skin on the abdomen. Jaundice is caused by the inability of a poorly functioning liver to process bilirubin, a breakdown product of red blood cell haemoglobin. Early liver problems may not be clearly symptomatic, and when jaundice occurs, liver damage has often progressed further. However, the liver has a large capacity and can compensate for dysfunctional parts.

Liver disease can be examined by means of blood and urine tests, X-rays, ultrasound, or by taking a biopsy of the liver. While blood liver enzymes ​​do not provide a prognosis for the disease, monitoring them can determine whether the disease is progressive, curative, or chronic. Ultrasound is used to examine the blood vessels, gallbladder, and bile ducts in particular, and a liver biopsy can be performed to detect the presence of tumour cells.

Chronic or acute hepatitis

Chronic hepatitis is the most common liver disease in dogs. Some breeds have an increased hereditary susceptibility to hepatitis. Examples of such breeds are the Bedlington Terrier, Labrador Retriever, Dobermann, and English Springer Spaniel. The cause of chronic hepatitis often remains unclear, but autoimmune hepatitis, infections, and poisonings are the most common cause. In chronic hepatitis, the inflammatory reaction of the liver becomes chronic, and the destruction of liver tissue gradually leads to liver failure and eventually cirrhosis. The disease can be detected by changes in the liver biopsy. Early detection of the disease improves prognosis. Treatment of the disease aims to slow the progression of liver failure, control hepatitis, and reduce hepatic tissue scarring. Acute hepatitis, or acute liver damage, can occur during sepsis, shock, or intoxication. Liver injuries and traumas can also cause acute liver damage. Liver function disorders are often associated with neurological symptoms or blood clotting problems.

Poisoning

Many drugs and toxic substances can cause changes in liver function that can become chronic and lead to liver failure. Sources of poisoning in dogs include drugs, xylitol, dark chocolate, certain plants, fungi, cyanobacteria, and moulds ingested through food. In case of acute poisoning, the dog should be taken to a veterinarian, and knowing what toxic substance the dog has ingested will increase the chances of successful treatment.

Infections

Many types of infections can affect a dog’s liver, including bacterial, viral, fungal, and parasitic diseases. Viral diseases include infectious canine hepatitis (hepatitis contagiosa canis) caused by canine adenovirus 1 and canine herpesvirus. Clostridium, mycobacteria, and leptospirosis can cause bacterial liver disease. Toxoplasmosis is an example of a parasitic disease that can affect liver function.

Hepatic encephalopathy

Hepatic encephalopathy is a syndrome of various neurological symptoms resulting from impaired liver function and can occur in a variety of liver diseases. The mechanism of development of the syndrome is not yet fully understood, but it is related to the impaired ability of the liver to remove various waste products from the systemic blood circulation as well as to changes in amino acid metabolism due to hepatic dysfunction.

The symptoms of hepatic encephalopathy in dogs are mainly neurological: poor coordination, dullness, head pressing, weakness, dementia-like symptoms, aimless wandering, and behavioural changes such as aggression and incomprehension of basic commands. A dog may also drool excessively, collapse, experience seizures, or fall into a coma. In the acute treatment of hepatic encephalopathy, the aim is to eliminate the ammonia and toxins causing the state of intoxication and correct dehydration and salt imbalances. The diet of a dog with hepatic encephalopathy should be changed to support liver function and decrease the production and circulation of neurotoxins.

Portosystemic shunts and other vessel abnormalities

A portosystemic shunt, or liver shunt, refers to a vascular malformation in the liver. In a shunt patient, the portal vein, which normally carries venous blood to the liver from the intestinal capillaries, bypasses the liver and connects directly to the systemic bloodstream through the shunt vessel. The shunt may be congenital, but in some instances it develops as a result of an illness, in which case it is referred to as an acquired shunt. Dogs can have intrahepatic (inside the liver) or extrahepatic (outside the liver) shunts. Certain breeds have an increased susceptibility to congenital portosystemic shunts. A portosystemic shunt causes small body stature, neurological symptoms, increased drinking and urination, and gastrointestinal symptoms. The condition can be diagnosed by a liver function test examining ammonia and bile acid. The shunt vessel may be visualized with ultrasound, and imaging can also assess liver size, enlarged kidneys, and the presence of bladder stones, which occur frequently in shunt patients. A portosystemic shunt can lead to hepatic encephalopathy. Depending on the location of the shunt, attempts can be made to treat it surgically. A special diet to support liver function should be initiated to decrease the neurological signs of hepatic encephalopathy.

Copper storage disease

In copper storage disease, copper accumulates in the liver. Copper storage disease is hereditary especially in Bedlington Terriers. Copper storage disease renders a dog’s liver unable to break down copper, which begins to accumulate in the liver cells, causing damage and leading to chronic hepatitis.

Things to consider in your dog’s diet

Protein restriction

When proteins break down, they produce ammonia. Excessive protein in food increases the production of ammonia in the body, and that puts extra strain on the liver. The amount of protein in the diet of a dog with liver disease should be low. There must be some protein in the food, but only enough to prevent the body from trying to break down muscle tissue, which in turn leads to muscle catabolism and the formation of ammonia. Because bacteria in the colon produce ammonia when they break down proteins, the source of protein in the diet should have high bioavailability for easy absorption in the small intestine.

Fats and energy

A dog suffering from liver disease often has increased energy demands. Because dogs with liver disease cannot consume large quantities of protein, they need a diet with a higher content of fat. In fact, they should get most of their energy from food containing high-quality fats. The diet should also provide plenty of omega-3 fatty acids, which have beneficial anti-inflammatory properties.

Limiting the amount of copper

Copper may accumulate in the liver of a dog with liver disease, which is why the copper content of the diet should be low. The accumulation of copper can further damage liver cells.

Vitamins and trace elements

The liver is involved in the synthesis of several vitamins in the body, and liver disease can cause disturbances in vitamin production. Important vitamins are B, C, and K but also vitamin E, which acts as an antioxidant for fats. The trace element zinc can help neutralize ammonia. The diet of liver patients should be low in salt, which can raise blood pressure and cause fluid to accumulate in the abdominal cavity.

Probiotics and prebiotics

The probiotic E. faecium and prebiotic fibre promote the growth of beneficial bacteria in the gut, which support the liver by binding ammonia. Certain types of prebiotic fibre can reduce the amount of ammonia produced by bacteria. Probiotics and prebiotics also improve the integrity of the intestinal wall.

Silymarin

Silymarins are flavonolignans obtained from the seeds of the milk thistle (Silybum marianum). Of these, the most important compound for liver function is silybin. The antioxidative properties of silymarins have been shown to protect and enhance liver function; for example, they increase levels of the body’s most important antioxidant, glutathione, which helps with liver reactions that convert fat-soluble compounds to a water-soluble form for elimination from the body. Many toxins are initially fat soluble. Silymarins also protect liver cells and stimulate liver cell metabolism.

Brit VD Hepatic

Brit VD Hepatic is a dietary food for dogs with impaired liver function or established hepatic impairment. It is suitable for dogs with hepatic encephalopathy due to impaired liver function as well as for dogs suffering from portosystemic shunt disease. It is also an effective supporting diet to improve liver function during recovery from poisoning. Brit VD Hepatic is indicated for dog breeds with a predisposition to copper storage disease, such as the Bedlington Terrier, Dobermann, West Highland White Terrier, Labrador Retriever, and Sky Terrier.

The source of protein in Brit VD Hepatic is highly absorbable and digestible egg protein, which naturally contains a larger proportion of essential amino acids than many other animal protein sources. The low protein content and excellent digestibility help reduce the formation of ammonia in the colon. Taurine and L-carnitine help prevent muscle catabolism and promote fat metabolism. The gluten-free and chicken protein-free composition of Brit VD Hepatic helps reduce the risk of AFR, while the high energy and fat content help maintain adequate energy intake if the dog’s appetite is reduced. Brit VD Hepatic is rich in both soluble and insoluble prebiotic fibre. The optimal concentration of fibre increases intestinal motility, slows the absorption of ammonia back into the bloodstream, and relieves nausea in anorexic dogs. The live probiotic E. faecium promotes healthy intestinal bacterial flora and the integrity of the intestinal wall.

Probiotics and prebiotics can reduce gastrointestinal symptoms because of their ability to bind uremic toxins and ammonia. Omega-3 fatty acids have anti-inflammatory properties and can prevent inflammation of liver tissue. The antioxidants selenium, vitamin E, and vitamin C promote normal immune system function. Silymarins have been shown to have hepatocellular protective properties and can help slow the destruction of liver tissue and even cure mild changes in liver cells. The reduced copper content prevents the accumulation of copper in the liver. Transitioning to the Brit VD Hepatic diet should be a gradual process.