INTERNAL MEDICINE
or preparation and resulting in decreased liver function. The nomenclature has recently been clarified by
WSAVA Standards.
The most common presentation is in young dogs
with stunted growth and/or abnormal mentation, but
more subtle signs of PSVA (eg, GI, PU/PD, weight loss,
lethargy, poor hair coat) in older pets are increasingly
appreciated; other signs are generally related to the
nervous or urinary system.
Serum biochemistry profile and urinalysis may reflect
the dysfunction (ie, low or low-normal glucose, cholesterol, albumin, BUN, microcytic anemia or target
cells, ammonium biurate crystalluria); however, preand postprandial serum bile acids testing (not liver
enzyme elevation) may best establish decreased liver
function, although it is not specific to PSVA.
When the clinical presentation and serum bile acids
test are consistent with decreased liver function, PSVA
can be confirmed and characterized by abdominal ultrasonography.
A single extrahepatic (small breed) or intrahepatic
(large breed) shunt is frequently visualised. Advanced
imaging or histopathology can be used if ultrasonography is equivocal or if primary portal vein hypoplasia
(formerly microvascular dysplasia or noncirrhotic
portal hypertension) is suspected. It is necessary to
determine whether the PSVA patient requires surgical
(most single shunts) or nonsurgical (primary hypoplasia, multiple acquired shunts) treatment.
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Medical management includes dietary intervention
(low-quantity, high-quality protein) and pharmaceutical manipulation of gut ammonia production (lactulose, 0.5 mL/kg q8–12h; neomycin, 22 mg/kg q8h).
5
“Nonhepatic” hepatic disease
Nonhepatic liver disease includes the following reactive hepatopathies: vacuolar hepatopathy, steroid
hepatopathy, and benign nodular hyperplasia. Elevations in liver enzyme activities do not necessarily indicate primary liver disease.
The liver senses various conditions or diseases and reacts with enzyme elevations; hence the term reactive
hepatopathy. Overlooking these differentials may lead
to unproductive diagnostic efforts. Steroids and anticonvulsants can induce elevated canine liver enzyme
activities. Benign nodular hyperplasia in older dogs
can mimic enzymatic and ultrasonographic changes
similar to those seen in neoplastic disease.
Growth in young dogs, bone cancer in older dogs,
and endocrinopathies (eg, Cushing’s disease, diabetes
mellitus) can result in elevated liver enzymes. (ALP)
Idiopathic vacuolar hepatopathy is a histopathologic
diagnosis consistent with exogenous steroid administration, Cushing’s disease, or other systemic illness.
After identifying and treating the primary disease, nonspecific therapy (eg, antioxidants) aimed at the liver
may be administered. Elevated liver enzymes in a
dog without clinical signs may be reevaluated in 4 to
6 weeks before pursuing a more extensive diagnostic
work-up.
Closing thoughts
The liver is involved in most every aspect of life. Therefore, primary liver disease makes the list of differentials
for most presentations, while secondary liver involvement must be considered in most nonliver diseases.
References available on www.vet360.vetlink.co.za
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