Hepatitis in dogs: symptoms, tests and treatment

Overview

Hepatitis is a group of inflammatory changes with different causes rather than a single uniform disease. Acute inflammation may be associated with leptospirosis or toxic exposure, for example. Chronic inflammation damages liver cells, which may be replaced by fibrous tissue. Cirrhosis is the end stage of advanced chronic hepatitis.

Raised liver enzymes do not always mean chronic hepatitis. The liver may react to disease elsewhere in the body without having chronic hepatitis itself. Up to 20% of dogs with chronic hepatitis have raised liver enzymes without visible illness. Clear signs of liver failure may therefore appear only later in the disease.

Causes

Copper, medicines and the immune response

Excessive copper accumulation in the liver is an important cause of chronic inflammation. Accumulation may result from an inherited handling disorder, high intake or a combination of the two. Free copper increases oxidative stress and damages liver cells.

In immune-mediated hepatitis, the body's immune response sustains inflammation in liver tissue. Diagnosing it requires other possible causes to be excluded. In some cases, the precise origin of inflammation cannot be established.

Medicines and toxic substances can also cause acute or chronic liver damage. Some epilepsy medicines and chemotherapy agents, for example, carry a recognised risk of chronic liver damage. Long-term medicine exposure is therefore assessed when investigating the cause.

Infectious canine hepatitis is a separate form

Infectious canine hepatitis is caused by canine adenovirus, which targets liver cells and cells lining blood vessels. Leptospira bacteria can cause acute hepatitis and sometimes chronic changes. There is no strong evidence that all chronic hepatitis has a viral cause. A hepatitis diagnosis therefore does not automatically mean an infectious viral disease.

Risk factors

Chronic hepatitis occurs in all breeds and in crossbred dogs. Predisposed breeds include Dobermanns, Labrador Retrievers, Dalmatians and English Springer Spaniels. Bedlington Terriers and West Highland White Terriers also have a recognised predisposition to copper-associated disease.

Across records for 983 dogs, the average age when signs began was 7.2 years. However, disease can begin considerably earlier and progress with few signs for a long time. Females are overrepresented among Labrador Retrievers and Dobermanns. In Cocker Spaniels, males have a greater predisposition. Liver disease in relatives and inherited differences in copper metabolism may increase an individual dog's risk.

Typical symptoms

Early signs are usually vague, so your dog may seem almost healthy for a long time. Reduced appetite and tiredness are more common than clear signs of liver failure.

• Your dog eats less or misses meals.
• Your dog is tired, subdued or less willing to exercise.
• Weight gradually falls without deliberate weight loss.
• Your dog vomits or has repeated diarrhoea.
• Increased thirst is accompanied by increased urination.
• The gums, skin or whites of the eyes become yellow.
• The abdomen enlarges because fluid accumulates.

Advanced disease may cause black stools or nosebleeds. Hepatic encephalopathy can cause behavioural changes and neurological signs. These signs indicate impaired liver function, rather than raised liver enzymes alone.

Among 294 dogs with chronic hepatitis of various causes, 61% had reduced appetite. Tiredness or depression occurred in 56% of these dogs. Jaundice was found in 34% of the same group.

Complications and consequences

Fibrosis, portal pressure and liver failure

Ongoing inflammation can replace functioning liver tissue with fibrous tissue and alter the organ's structure. Pressure in the portal venous circulation may rise, causing abdominal fluid accumulation called ascites. New shunting vessels may open, allowing blood to bypass the liver. Encephalopathy can develop even without an increased blood ammonia level.

A tendency to bleed has been described in around 6–7% of dogs with chronic hepatitis. Some patients may instead clot excessively, creating a risk of thrombosis. Reduced blood albumin indicates impaired liver function. Raised bilirubin and low albumin are often associated with a poorer outlook.

Disease stage matters more for prognosis than a single liver enzyme result

The pooled average survival of 364 dogs with chronic hepatitis was 561 ± 268 days. Among 39 dogs with biopsy-confirmed cirrhosis, average survival was only 23 ± 23 days. These dogs received various medicines and diets. In contrast, copper-associated hepatitis recognised early can have a good outlook.

The height of liver enzyme levels does not directly predict survival. Early treatment may keep chronic inflammation controlled for several years. Your dog's individual outlook depends on both the cause and the stage at diagnosis.

Diagnosis at the vet

Liver enzymes and function tests measure different things

Your vet asks about the duration of signs, medicines used and possible toxic exposures. ALT leaks into the bloodstream from damaged liver cells and is often an early finding. An unexplained ALT increase lasting more than 2 months warrants investigation for chronic hepatitis. The liver enzyme ALP may rise later in the disease. In end-stage cirrhosis, ALT may fall even as liver function deteriorates.

Bile acids, bilirubin and albumin help assess liver function. Normal bile acids do not exclude early chronic hepatitis. Clotting times and platelets are checked before a liver biopsy. Urinalysis may reveal associated protein loss or abnormal glucose excretion.

Ultrasound guides biopsy investigation

Ultrasound assesses liver size and structure, the bile ducts and major blood vessels. It may also show abdominal fluid, abnormal vessels or blood clots. A normal ultrasound does not exclude chronic hepatitis.

Confirming chronic hepatitis requires histological examination of a liver biopsy to assess tissue structure. Fine-needle cytology can investigate other causes but does not confirm chronic hepatitis. The biopsy shows the type and severity of inflammation and the amount of fibrosis. Copper staining and copper measurement form part of the investigation.

At least 5 biopsies from at least 2 liver lobes are recommended for the different tests. Samples can be used for bacterial culture and copper measurement as well as histology. Laparoscopy allows adequate biopsies from several sites through a relatively minor procedure. With a high bleeding risk, monitoring for 12–24 hours after biopsy may be needed.

Treatment

Treatment targets the cause of inflammation

Your vet chooses treatment based on the biopsy, copper concentration and your dog's overall condition. Bacterial hepatitis requires antimicrobial treatment appropriate to the organism. In infectious adenoviral hepatitis, treatment supports fluid balance, liver function and clotting. A medicine or supplement suspected of damaging the liver is stopped according to your vet's plan. Recovery is then monitored with repeated blood tests.

Copper-associated hepatitis is treated with a low-copper diet and copper-removing medication. This medication binds copper and increases its removal in urine. Copper-removing treatment is generally prolonged. Severe accumulation in a Bedlington Terrier may require particularly prolonged or lifelong medication. Dietary copper restriction is usually lifelong in copper-associated hepatitis.

Immune-mediated inflammation needs carefully considered immunosuppression

Immunosuppressive medication is based on the inflammatory pattern in the biopsy and assessment of other causes. Treatment may involve a corticosteroid or other medicines affecting the immune response. Medication is adjusted according to your dog's response and adverse effects.

Corticosteroids can increase thirst, urination and appetite. They can also raise liver enzymes, making response harder to assess from blood tests alone. Suppression of immunity may be associated with problems such as a urinary tract infection without signs. Certain medicines can also cause digestive problems or impaired bone marrow function.

There is no single defined treatment duration for all dogs with immune-mediated hepatitis. Many need long-term treatment and regular health assessments. Sometimes another liver biopsy is needed to confirm that inflammation has subsided.

Nutrition and treatment of liver failure complete the plan

Protein does not generally need restricting in every dog with chronic hepatitis. In hepatic encephalopathy, however, protein quantity and quality may be adjusted individually. Liver disease alone also does not generally require fat restriction. A commercial low-copper diet may need additional protein if its protein content is insufficient for your dog.

Antioxidants and products protecting liver cells can support other treatment. They do not replace treatment of an identified cause. Vitamin K is not routinely needed by every patient: its use depends on factors such as clotting disorders and bile secretion. Treatment of abdominal fluid and portal circulatory changes is planned separately alongside other liver care.

Prevention

Vaccination included among dogs' core vaccines can prevent infectious adenoviral hepatitis. However, vaccination does not prevent hepatitis caused by copper, medicines or an immune reaction.

Breed-specific genetic testing and breeding decisions can help address a known inherited predisposition affecting copper metabolism. A genetic result does not identify every cause of liver disease. Recognising exposure to medicines and supplements harmful to the liver helps prevent further damage. Persistent unexplained liver enzyme increases are investigated even in dogs without signs.

Important for dog owners

Record appetite, weight changes, vomiting and diarrhoea for follow-up appointments. Watch for changes in drinking, urination, abdominal size and mucous membrane colour. Abnormal behaviour or confusion may indicate encephalopathy associated with impaired liver function.

Bring details of all medicines and supplements, as these can also be associated with liver damage. During immunosuppressive treatment, increased thirst may be an adverse effect of medication rather than worsening disease. Liver blood results are interpreted alongside medication, signs and any biopsy findings.

Treats and supplements count towards the overall low-copper diet. Monitoring continues when signs improve, as chronic disease may require long-term maintenance treatment.

Frequently asked questions

Is hepatitis always infectious?

Hepatitis can result from infection, but also from copper accumulation, a medicine or immune-mediated inflammation. Infectious canine hepatitis caused by adenovirus is a distinct form of disease. The word hepatitis alone therefore cannot determine whether it is infectious: tests must establish the cause.

Does a high ALT mean liver failure?

ALT leaks from damaged liver cells, and its level does not directly measure the liver's ability to function. Liver function is assessed using factors including bile acids, bilirubin and albumin. In end-stage cirrhosis, ALT can even fall as the number of liver cells decreases.

Why is a liver biopsy needed?

A biopsy reveals the type of inflammation, fibrosis and copper accumulation, which influence treatment choice. Ultrasound or fine-needle cytology alone cannot confirm chronic hepatitis. Samples can also investigate a possible bacterial cause and measure tissue copper. Your dog's clotting is assessed when planning sampling.

Does a dog with liver disease need a low-protein diet?

Protein is not generally restricted in every dog with chronic hepatitis. Restriction may be needed in hepatic encephalopathy, but the diet is tailored to your dog's condition. Reducing copper is central to copper-associated disease, and a low-copper food may sometimes need additional protein.

Can a dog recover from chronic hepatitis?

Disease can remain controlled for several years if recognised and treated early. The outlook depends on the underlying cause and the extent of liver damage. Advanced cirrhosis substantially worsens the outlook, and many dogs need long-term care and monitoring.