If you’re a dog lover like me, you’ll do just about anything to keep your pup happy and healthy. 

But what happens when you find out they have something abnormal going on in their liver? Your first thought is probably, “Oh, NO!” It sounds bad but not all dog liver problems are scary. 

Liver nodular hyperplasia may not be a household term, but it’s a condition that affects many dogs. Unfortunately, the name of the condition doesn’t do much to clear up the confusion about what it is. 

In this article, we’re going to delve into this common but mysterious condition and provide you with everything you need to know. From the causes and symptoms to diagnosis and treatment options, we’ll cover it all. 

Why Is a Dog’s Liver So Important?

The liver is a large organ located in the front part of a dog’s abdomen. It’s one of the most important organs in a dog’s body, performing several vital functions. 

  • Bile production helps digest fats in the intestine
  • Mineral, glycogen and triglyceride storage
  • Fat, protein and carbohydrate metabolism
  • Glucose and glycogen metabolism
  • Toxin and drug removal from the blood
  • Blood clotting factor production
  • Helps develop blood cells
  • Helps with immune responses

When a dog’s liver becomes diseased, it can affect many aspects of health. That’s why veterinarians and pet owners get anxious when they find a liver abnormality. 

Some liver abnormalities are deadly (like cancer) while others are not so bad (like vacuolar hepatopathy). Nodular hyperplasia in a dog’s liver falls at the “not so bad” end of the spectrum. 

What Is Liver Nodular Hyperplasia in Dogs?

Liver or hepatic nodular hyperplasia (HNH) is a condition in which a dog’s liver develops one or more abnormal nodules. The nodules indicate a change in the hepatic cells that make up the liver. HNH nodules are visible to the naked eye during surgery or post-mortem exam as well as on ultrasound imaging. 


A 1985 paper published in Veterinary Pathology found 35 out of 50 post-mortem exams on dogs found HNH lesions. Nodules were present in dogs as young as 6 years and all dogs over the age of 14 years had HNH. 

The researchers found that liver nodular hyperplasia lesions were caused by an increase in the size and number of fat storage cells, increased presence of macrophages (white blood cells), and increased presence of pigment. (1)

The exact triggering factor of HNH is unknown.

Senior dog lying down (liver nodular hyperplasia in dogs)

Is Hepatic Nodular Hyperplasia in Dogs Bad?

HNH is very common in senior dogs over 11 years of age. No particular dog breed or sex seems to have a higher risk of developing the condition than average

Here’s the good news: HNH is a non-cancerous condition that does not affect normal liver function. You can think of the condition as something found in senior dogs, usually by coincidence, while looking for something else. 


Since HNH does not cause liver dysfunction, it doesn’t cause any physical clinical signs. The only way veterinarians know it’s there is by finding it during surgery, on imaging or a liver biopsy. 

It can cause elevated liver enzymes, especially alkaline phosphatase (ALP). Occasionally, liver tests for alanine transaminase (ALT) and aspartate aminotransferase (AST) are also increased. But these changes don’t cause physical symptoms in dogs with HNH.

Learn more about canine liver disease

Blue heeler dog lying on floor


When found during abdominal surgery or on radiographs, ultrasound imaging or CT scan, HNH has the same appearance as a cancerous liver tumor. Biopsy or cytology analysis is necessary to distinguish between HNH and liver cancer.

Small liver samples are collected with a syringe and needle using ultrasound guidance. This method has the advantage of not requiring full anesthesia to collect. The disadvantage is that the small sample can sometimes miss the actual liver lesions of concern. 

A liver biopsy can be collected with a large bore needle through the skin with ultrasound guidance. Biopsy samples are also collected during abdominal surgery. These biopsies require heavier sedation or anesthesia but are more likely to represent the liver tissue in question.

Pathologists at reference labs examine the cytology samples and biopsies. They look at the liver cells microscopically for characteristics of HNH vs. cancer. With a representative sample, the odds of getting an accurate diagnosis are high.

Treatment & Follow-Up

No treatment is available or needed for HNH since it doesn’t affect liver function. Small HNH nodules are unlikely to rupture and cause bleeding like cancerous tumors. (2)

The prognosis for HNH is good and it’s not a precursor for cancer. 

But because liver conditions change over time, your vet may want to monitor the dog’s liver enzymes, radiography or ultrasound imaging periodically.

You can help your dog at home by watching them for changes in appetite, thirst and activity level. Senior dogs benefit from vet checkups every 3-6 months. Keep a list of your observations and discuss them with your veterinarian.


Hepatic nodular hyperplasia (HNH) is a condition that affects many senior dogs, characterized by the development of one or more abnormal liver nodules. The exact cause of HNH is unknown, but it is not a cancerous condition and does not affect liver function. HNH is typically discovered by coincidence during diagnostic imaging or abdominal exploratory surgery. 

Veterinarians may recommend monitoring the dog’s liver enzymes periodically and repeating imaging studies, but no treatment is necessary. While HNH doesn’t cause symptoms, pet owners should still watch for changes in their dog’s appetite, thirst, and activity level and report concerns to their veterinarian during regular check-ups.

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  1. Bergman, J. R. (1985). Nodular hyperplasia in the liver of the dog: an association with changes in the Ito cell population. Veterinary Pathology, 22(5), 427-438.
  2. Pintar, J., Breitschwerdt, E. B., Hardie, E. M., & Spaulding, K. A. (2003). Acute nontraumatic hemoabdomen in the dog: a retrospective analysis of 39 cases (1987–2001). Journal of the American Animal Hospital Association, 39(6), 518-522.
  3. Functions of the Liver. (n.d.). https://www.merckvetmanual.com/. Retrieved February 28, 2023, from https://www.merckvetmanual.com/SearchResults?query=liver+function