Understanding Vacuolar Hepatopathy (VH), a Liver Disease in Dogs
Vacuolar hepatopathy can seem like a complicated topic. To help us understand it better, let’s break it down:
- Hepatopathy— The ‘hepato’ part of the word, hepatopathy, refers to the liver and the ‘pathy’ part refers to a disease. So hepatopathy is a disease of the liver.
- Vacuolar— Vacuolar is the adjective that specifies the type of disease with ‘vacuoles’ being cysts or vesicles that form inside of the cells themselves.
According to David Twedt (DVM;DACVIM) of Colorado State University, with vacuolar hepatopathy (VH), the cysts can fill with different substances from water or fats to cellular waste products or glycogens. In dogs, however, MERCK reports that VH commonly involves glycogens. That will be the focus of this article.
Why do these vacuoles form?
Any time that liver cells are stressed or damaged, one of their responses is to swell and to develop vacuoles. Unfortunately, this means that the list of possible causes for vacuolar changes is quite extensive. In fact, any other ongoing disease process (stress, inflammation, infection, cancer, etc) in the liver or in any other organ systems can cause the vacuolar changes to occur. This is because natural glucocorticoids or cortisols (internally produced steroids like the prednisone you may have given your dog for something like allergies or itchy skin) are released by the adrenal glands as a general response to illness.
There is also a specific disorder in dogs called hyperadrenocorticism (Cushing’s Disease) wherein a dog’s adrenal glands persist in releasing an abnormally high level of cortisol. And yes, the prednisone that you might need to give to your dog can also cause the same reactive changes.
Administering phenobarbital (usually to control seizures) can also cause these changes. In addition, there are cases of VH that occur in dogs with normal cortisol levels, according to Twedt’s report, and Scottish Terriers exhibit a breed-specific VH syndrome.
How would you even know that the vacuoles are there?
You won’t know for sure unless your veterinarian obtains a biopsy sample of your dog’s liver for evaluation. Since getting a liver sample requires some degree of commitment and risk, your veterinarian will first recommend some other tests. These will probably be more routine and less invasive tests.
Most likely, the process will have begun with basic blood tests: complete blood count and serum biochemistries. These tests may have been run because your dog is exhibiting some signs of illness; or symptoms specific to Cushing’s Disease (such as increased thirst, urination and/or appetite); or as a routine geriatric or pre-anesthetic protocol. In cases of VH these tests will reveal at least a few abnormalities, but the hallmark of the disease is a marked increased in a specific liver enzyme, alkaline phosphatase.
As with most potentially serious conditions a complete evaluation should include a complete urinalysis to check for urinary tract infections and clues to possible causes of the vacuolar liver disease. Your veterinarian may then recommend imaging the liver itself via radiographs (X-Rays) and/or ultrasound. But again, ultimately, the definitive diagnosis will require a biopsy. The biopsy is also valuable to diagnose or exclude other types of liver disease that might behave more aggressively. Also remember that your veterinarian may still need to pursue more testing to determine if/what underlying disease process may also be involved with VH.