The Most Common Liver Diseases in Dogs

To understand the causes of liver diseases, we should first clarify that liver diseases can be divided into four major groups:

• Alterations in the liver parenchyma: both inflammatory (hepatitis with or without cirrhosis) and non-inflammatory (hepatic amyloidosis, hepatic lipidosis, and steroid liver disease).
  
  
• Tumor diseases: Lymphoma, hepatocellular carcinoma, cholangiocarcinoma, or liver metastases.
  
  
• Alterations in the biliary system: cholangitis, cholecystitis, or mucocele.
  
  
• Disorders of the hepatic circulation: portosystemic shunts and hepatic congestion.

After identifying the different groups of liver diseases, we will elaborate on the causes of each group.

Congenital alterations

These are defects that are present from birth. One of the liver diseases caused by congenital alterations is congenital portosystemic shunts (PSS). Dogs born with this alteration have an abnormal connection between the portal and systemic circulations.

Portal hypertension

Portal hypertension is increased pressure in the portal venous system, which is responsible for transporting blood from the intestines to the liver. The most common cause of portal hypertension is cirrhosis (scarring) of the liver.

Endocrine diseases

Some endocrine diseases can secondarily lead to hepatic alterations. Here are some of the most common examples:

• Cushing's syndrome: It is associated with the onset of steroid liver disease and it occurs when your dog's body produces too much cortisol over time. Cortisol is sometimes called the "stress hormone" because it helps your dog's body deal with stress.
  
  
• Diabetes mellitus: commonly known as diabetes, is a group of metabolic disorders characterized by persistently high blood glucose levels. It is associated with the development of hepatic lipidosis, which consists of a pathological accumulation of triglycerides in hepatocytes.

Contagious diseases

In dogs, there are several pathogenic microorganisms that can affect the liver and cause hepatitis. The main infectious and parasitic diseases associated with chronic hepatitis in dogs are:

• Canine viral hepatitis
• Ehrlichiosis
• Leishmaniasis
• Leptospirosis
• Neosporosis
• Histoplasmosis
• Toxoplasmosis

Drugs and toxins

There are certain drugs and toxic compounds that can cause liver disorders. Here are some examples:

• Glucocorticoids: Anti-inflammatory drugs that work with your dog's immune system to treat a variety of health problems. They cause steroid liver disease, but it regresses when treatment is stopped.
  
  
• Hepatotoxic drugs: such as phenobarbital or lomustine, can cause chronic hepatitis followed by cirrhosis and liver failure.
  
  
• Copper: The accumulation of copper in the liver leads to chronic hepatitis. There are some breeds that are predisposed to copper accumulation, such as the Bedlington Terrier, the Labrador, the Dalmatian, the West Highland Terrier, or the Skye Terrier.
  
  
• Aflatoxins: Consumption of moldy foods containing this type of toxins may lead to the development of chronic hepatitis.

Tumors

These are among the most common liver problems in older dogs. Unlike in cats, most liver tumors in dogs are usually malignant. In particular, hepatocellular carcinoma is the most common liver tumor in dogs, followed by bile duct carcinoma.

To know more about cirrhosis, one of the most common liver diseases, do not miss out on this article on cirrhosis of the liver in dogs

The clinical presentation of liver problems in dogs, as in other animal species, is determined by two basic features of the liver:

• Its regenerative capacity: Liver regeneration is the process by which the liver is able to replace lost liver tissue by growth from the remaining tissue. The liver is the only visceral organ that has the ability to regenerate.
• Its large functional reserve: The liver does not need to use its full capacity to perform its functions. Only 30% of the liver is needed to maintain normal albumin levels, so the liver has a capacity of 70%.

For these reasons, it is common to observe patients with liver injuries that remain completely asymptomatic, as these injuries have not yet caused any functional change in the liver. When symptoms suggestive of a liver problem are observed, more than 70% of the liver parenchyma is generally affected.

After knowing these details about the liver, we will explain the three situations that we can find in dogs with liver problems.

Asymptomatic patients

They are those who are in the early stages of chronic disease. Since they are asymptomatic, we can only determine the presence of a liver problem by doing a blood test with a liver profile, which is usually done when dogs are undergoing general anesthesia for some other medical reason.

Patients with nonspecific signs

In these patients, nonspecific clinical signs are initially observed, i.e., they do not indicate a priori liver disease. The symptoms we can see in these dogs are:

• Digestive signs: bilious vomiting and diarrhea.
• Urinary signs: polyuria, polydipsia, hematuria and dysuria.
• Anorexia and weight loss.
• Low body condition.
• Apathy and depression.

Patients with signs suggestive of liver disease

These are patients with advanced liver disease in which the functional reserve capacity of the liver has been exceeded. Although the animal is suffering from a chronic disease, the symptoms usually appear acutely at the time when the liver can no longer perform its functions because its functional reserve has been exceeded.

The clinical signs that we can observe in dogs in these conditions are:

• Jaundice: yellowish discoloration of the mucous membranes. It is due to an excess of bilirubin (a yellow pigment) deposited in the tissues. In dogs, it is usually first noted in the sclera.
  
  
• Ascites: Abdominal dilatation due to build-up of fluid in the abdomen.
  
  
• Hepatic encephalopathy: When the liver loses its cleansing capacity, ammonia enters the bloodstream and eventually the central nervous system, resulting in a neurological condition. Signs that may occur in these dogs include an altered state of consciousness (lethargy, stupor, and eventually coma), weakness or ataxia, pressure of the head against the wall or floor, circling, and seizures. To know more about this liver disease, keep reading our article on hepatic encephalopathy in dogs.
  
  
• Tendency to bleed: as the liver is responsible for the synthesis of clotting factors.
  
  
• Urinary signs: such as dysuria (painful urination) and hematuria (bloody urine). They usually occur in dogs with portosystemic shunts, as a result of the formation of ammonium urate stones in the urine.

A diagnostic protocol for dogs with liver problems includes the following items:

• History and general examination: in asymptomatic dogs or dogs with only nonspecific signs, it is difficult to suspect a liver problem. In dogs with signs suggestive of liver disease, it is easier to make the diagnosis. However, it must be kept in mind that the signs are very similar in most liver problems, so the clinical picture usually does not provide information about the specific liver disease. Moreover, it is not possible to determine from the symptoms whether the case is acute or chronic, because, as we have already explained, the signs in patients with chronic diseases usually appear acutely, when the functional capacity of the liver is exceeded.
  
  
• Blood analysis with liver profile: if the animal's clinical signs suggest biliary disease, a blood analysis should be performed to determine values such as total proteins, albumin, liver enzymes, ammonia, glucose and bile acids.
  
  
• Urine examination: urine density and bilirubin should be measured, especially if the urine is very heavy and pigmented. It is also useful to examine the urine sediment for ammonium urate crystals.
  
  
• Other laboratory tests: in addition, more specific laboratory tests may be performed, such as measurement of fasting bile acids or the ammonia overload test.
  
  
• Abdominal ultrasound: this imaging test can evaluate the liver parenchyma, biliary system, and vascular system. It can be used to diagnose some liver diseases such as portosystemic shunts or extrahepatic biliary obstruction. However, a negative ultrasound does not rule out the presence of liver disease because changes in the liver parenchyma do not produce a diagnostic ultrasound image.
  
  
• Radiography of the abdomen: radiography should provide information about the size of the liver, since ultrasonography usually gives a somewhat subjective idea. In acute pathologies, the size of the liver is normal or increased, while in chronic cases it is decreased.
  
  
• Magnetic resonance: this advanced imaging study is particularly useful for the diagnosis of vascular pathologies of the liver, pathologies of the biliary system and tumors.
  
  
• Fine needle aspiration procedure: used to perform cytology. This test can detect abnormalities in hepatocytes (liver cells) such as lipidosis, steroid liver, amyloidosis, or tumors. However, in dogs, this test is diagnostic in only 30% of cases.
  
  
• Biopsy:Hematological analysis is performed in dogs for whom FAP is not diagnostic. The sample is obtained percutaneously with biopsy needles or surgically (via laparotomy or laparoscopy).

Treatment of liver problems in dogs may include one or more of the following:

• Medical treatment: depending on the specific pathology, it may be necessary to correct hydroelectrolytic imbalances with fluid therapy. It is also advisable to supplement for vitamin deficiencies (with vitamin K, thiamine, cobalamin), as well as to treat digestive disorders and/or neurological signs. Some cases require to administer hepatoprotective medications such as ursodeoxycholic acid.
  
  
• Dietary management: in general, a well-digested diet rich in easily assimilable carbohydrates and low in fat should be administered. The levels of protein, sodium and copper in the diet should be adjusted according to the specific pathology of the dog.
  
  
• Surgical treatment: it will be necessary in some pathologies such as portosystemic shunts or liver tumors.
  
  

For a successful treatment, it is also important to know if it is a primary liver disease (that is, it originates in the liver itself) or if it is a consequence of another disease. In the latter case, we must also treat the primary pathology to treat the liver disease.

In order to prevent possible liver problems in dogs, the following factors must be considered:

• Vaccination and deworming: as we have already explained, there are numerous microorganisms and parasites that can cause liver disease. For this reason, it is important to keep the dog vaccination and deworming program up to date to prevent these diseases.
  
  
• Control of other pathologies: Pathologies that may be secondary to liver changes must be kept under control.
  
  
• Control of pharmacological treatments: In patients treated with hepatotoxic drugs, regular controls must be performed and the dose must be kept within therapeutic limits.
  
  
• Prevention of poisoning: by mycotoxins, hepatotoxic plants, etc.

Find out more about liver failures and how to prevent them in this article on liver failure in dogs.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

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