Page 677 - Clinical Small Animal Internal Medicine

60 Approach to the Patient with Liver Disease 645

described in several breeds, including the Bedlington ter- access to toxins and a history of any recent drug admin-
VetBooks.ir rier, Dalmatian, Doberman pinscher, Labrador retriever, istration are extremely relevant. The clinician should
maintain a high index of suspicion whenever a patient
West Highland white, and Skye terriers. A recent study
documented breeds at risk of developing chronic hepati-
a new drug. There are many known potentially hepato-
tis in the UK (see Chapter 64). These included three develops new clinical signs within four weeks of starting
breeds in agreement with a previous, older study from toxic drugs, common examples being phenobarbital
Sweden: the American and English cocker spaniel, and itraconazole, but most drugs have the potential
Doberman pinscher and Labrador retriever, and addi- for an idiosyncratic reaction in an individual patient.
tionally highlighted an increased risk in the cairn terrier, Consumption of a hepatotoxin is also possible, such as
English springer spaniel, Great Dane, and Samoyed. certain mushrooms, xylitol (contained in sugar‐free
However, it should be recognized that the gene pools in sweets) or even herbal/dietary supplements that the
different countries can vary, such that certain breed char- owner might be administering.
acteristics and predispositions may be more regional. Hepatobiliary disease can result in a very broad range
In addition to the breed, the age at onset of clinical of clinical signs reflecting both the sheer variety of func-
signs can be very helpful in aiding diagnosis of some tions the liver performs and the central role it plays in
hepatobiliary conditions. For example, animals with many metabolic and detoxifaction pathways. This cen-
CPSS typically present at a younger age. This has classi- tral role means that hepatic disease can result in the sec-
cally been described to be less than 1 year of age, although ondary dysfunction of other organs, as in HE. It also
increasingly older dogs seem to be recognized, presum- places the liver in a position where it can itself become
ably as clinicians are looking more widely for the condi- secondarily affected, for example with hyperadrenocor-
tion. There have been reports of increasing numbers of ticism or hepatic lipidosis. The net result is that the clini-
miniature schnauzers not being diagnosed until they are cian needs to be alert to this when approaching a case,
over 7 years, presenting with only mild signs. Reports aiming to first decide if hepatobiliary disease could be
looking at the age and gender distribution of dogs pre- present in an animal but then, importantly, whether this
senting with chronic hepatitis have shown the mean age represents a primary or secondary phenomenon. These
at diagnosis to be approximately 8 years when all breeds key questions sound very straightforward, but they can
were considered together, although some breeds tended be challenging to address in many patients and will be
to present at a younger age (e.g., English springer span- reconsidered as different aspects of the investigation of
iel). In general, females are overrepresented, although liver disease are explored.
again there are occasional breeds where this does not
appear to be the case.
Diagnosis
History and Clinical Signs
Biochemical Evaluation
A thorough history with good attention to detail is key to The employment of clinical pathologic testing is central
approaching any clinical case. This is particularly perti- to the approach to animals with hepatobiliary disease.
nent with potential hepatobiliary cases for a variety of In many cases, recognition of abnormal test results often
reasons. As outlined in the introduction, the large provides the first indication that liver disease may be
hepatic functional reserve means that in order to diag- present. It is not uncommon to detect high liver enzyme
nose diseases before there is significant, irreversible loss activities as the only abnormality on preanesthetic or
of healthy liver tissue, the clinician needs to identify health screens, prompting further investigation. In addi-
cases with subtle and often vague clinical signs. tion, as outlined above, in view of the typical presenta-
Symptoms such as anorexia, vomiting, lethargy or mild tion of hepatobiliary cases, it is important to use clinical
polyuria/polydipsia, which are often waxing and waning, pathology to aid in the diagnosis is liver disease early on
should alert the clinician that liver disease is a potential in the disease process. Often at this stage the clinical
differential diagnosis. The onset of clinical signs may signs may be vague and nonspecific with clinical pathol-
initially appear acute in nature but careful discussion ogy aiding greatly in the decision making and further
with the owner might elucidate a more chronic back- defining of such cases.
ground than initially described. Box 60.1 summarizes The laboratory evaluation of hepatobiliary patients has
clinical signs that may be observed in animals with several broad aims: to determine/confirm the presence
liver disease. of hepatobiliary disease and assess hepatic function, to
The potential for toxin exposure should always be con- aid in distinguishing primary or secondary hepatic
sidered so a detailed description of the animal’s potential disease and to contribute to diagnostic planning or