Pertinent historical information includes the administration of any potentially hepatotoxic drugs, supplements, or nutraceuticals;
exposure to any environmental toxins or infectious agents; recent anesthetic events; and details on housing, supervision outdoors,
travel, and vaccination status. Carefully question owners about any possible vague signs of underlying disease such as intermittent
gastrointestinal signs (e.g. vomiting, diarrhea, weight loss), behavioral changes, polyuria or polydipsia, or exercise intolerance. In the case of primary
hepatobiliary disease, clinical signs may not be apparent until the disease process is advanced because of the liver's large
regenerative capacity and functional reserve.
Several drugs have been associated with hepatotoxicity in dogs (Table 2).12 If a potentially hepatotoxic drug or supplement is being administered, discontinue it; if abrupt cessation is not possible,
taper the drug and add another drug of a different class. Liver enzyme activities should be reevaluated two weeks after discontinuation
of the suspected hepatotoxic agent. Persistent or progressive increases in liver enzyme activity indicate the need for further
Table 2: Drugs Associated with Acute Liver Disease in Dogs
Physical examination findings may include coat changes and hepatomegaly (due to hyperadrenocorticism), a stunted or pot-bellied
appearance and poor body condition (due to a portosystemic vascular anomaly), mild abdominal discomfort (due to chronic pancreatitis),
or thickened intestines (due to inflammatory bowel disease).
Signalment may be helpful since several breed-associated hepatopathies that are inflammatory, fibrotic, or both exist (Bedlington
terriers, cocker spaniels, dalmatians, Doberman pinschers, Labrador retrievers, Skye terriers, West Highland white terriers)
and portosystemic vascular anomalies have strong breed associations.10,11
IS FURTHER DIAGNOSTIC TESTING NEEDED?
Any elevation in liver enzyme activity in dogs of breeds predisposed to a hepatopathy or associated with portosystemic vascular
anomalies requires further diagnostic evaluation. In breeds predisposed to inflammatory hepatopathies, a hepatic ultrasonographic
examination with biopsy, culture, and quantitative copper analysis is recommended. In breeds predisposed to portosystemic
vascular anomalies, look for a shunt by performing an ultrasonographic study. If a shunt cannot be confirmed but is still
suspected, scintigraphy (colorectal or transplenic) can be considered. If a shunt is not identified by either ultrasonography
or scintigraphy, a wedge biopsy may be necessary to identify cases of microvascular dysplasia.
Further diagnostic testing is also indicated if the patient in question is not of a breed predisposed to a hepatopathy, has
no history of drug exposure, and has any of the following:
- An elevation of greater than three times the upper reference range limit in more than one enzyme activity
- A progressive increase in enzyme activities
- A single enzyme activity elevation and an increased bilirubin or decreased albumin concentration
In cases in which only a single liver enzyme activity is increased and the increase is less than three times the upper reference
range limit, you may choose to perform a bile acid assay or repeat the serum chemistry profile in four weeks.
Finding an abnormal total serum bile acid concentration at any point necessitates further evaluation. However, a normal total
serum bile acid concentration does not rule out liver disease.
Persistent and progressive increases in serum liver enzyme activities also require further evaluation.