The diagnostic approach to asymptomatic dogs with elevated liver enzyme activities - Veterinary Medicine
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The diagnostic approach to asymptomatic dogs with elevated liver enzyme activities
What's the next step when you see an apparently healthy dog that has abnormal liver enzyme results? These clinicians help you figure out when further diagnostic testing is warranted, which tests are indicated, and what conditions to suspect.


VETERINARY MEDICINE


History

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.

Drugs


Table 2: Drugs Associated with Acute Liver Disease in Dogs
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 diagnostic testing.

Physical examination

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

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.


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Source: VETERINARY MEDICINE,
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