Page 688 - Clinical Small Animal Internal Medicine

656 Section 7 Diseases of the Liver, Gallbladder, and Bile Ducts

In general, bacteriologic culture of bile yields far more well the animal will tolerate sedation or general anesthe-
VetBooks.ir positive results than culture of liver parenchyma. sia. The latter is particularly a consideration in patients
with signs of HE where medical management to stabilize
Histopathologic Evaluation
necessary. A minimum database to screen hemostatic
Indications the patient prior to more invasive procedures is often
As discussed earlier, the laboratory tests for liver disease function should include a platelet count, prothrombin
rarely identify a specific etiology. Having employed clini- time (PT), and partial thromboplastin time (PTT). The
cal pathology and ultrasonography as diagnostic tests to measurement of buccal mucosal bleeding time (after
identify potential liver disease, evaluation of a liver establishing a normal platelet count on a blood smear) is
biopsy aids the provision of a diagnosis and prognosis also recommended due to some reports of increased
and in guidance of therapeutic intervention. In general, a complications due to primary hemostatic abnormalities
liver biopsy is indicated in the following circumstances. (platelet dysfunction) rather than secondary hemostatic
(coagulation factor) abnormalities. Measurement of
Asymptomatic patients with persistent, serial eleva-
● fibrinogen along with fibrin degradation products (FDPs)
tions in liver enzyme activities.
Asymptomatic patients with abnormal hepatic func- and D‐dimers to assess for increased fibrinolysis might
● also be considered. However, it should be noted that
tion tests (e.g., fasting serum bile acid or postprandial there is often poor correlation between coagulation
serum bile acid).
Where hepatic parenchymal abnormalities are identi- parameters and major complications at liver biopsy.
● Although there is little veterinary literature published in
fied ultrasonographically.
Where there is unexplained hepatomegaly. the area, one study suggested that a platelet count below
9
● 80 × 10 /L, a PTT more than 1.5 times the reference
To assess response to therapeutic intervention.
● interval in cats and a PT above the reference interval in
Evaluation of animals with potential breed‐specific
● dogs were all associated with an increased risk of minor
hepatopathies.
Any animal with progressive signs of liver disease. complications in animals undergoing ultrasound‐guided
●
needle biopsies.
It is important to recognise the potential for the occur- Some clinicians suggest administration of vitamin K 24
rence of liver enzyme elevation and secondary “reactive” hours prior to biopsy in all cases. It is certainly appropri-
hepatopathies as a result of extrahepatic causes. ate to treat any patients with prolonged coagulation
Consideration of and, if appropriate, evaluation for the screens, as administration has been shown to improve
presence of potential extrahepatic causes, such as hyper- clotting times in many patients. The administration of
adrenocorticism in dogs, hyperthyroidism in cats and vitamin K to all hyperbilirubinemic patients, particularly
gastrointestinal or pancreatic disease, is important cats, is probably prudent in view of the role of bile in the
before pursuing a liver biopsy, particularly where only adsorption of fat‐soluble vitamins and the insensitivity
liver enzyme elevation is noted on a biochemistry panel. of PT and PTT in detecting bleeding diatheses. The use
The consideration of more than one liver enzyme activ- of fresh‐frozen plasma to deliver coagulation factors to
ity, evaluation of results on more than one occasion and patients with mildly increased PT and PTT is also an
performing a liver function test, such as pre‐ and post- option. Following a liver biopsy, it is essential that
prandial bile acids, can be helpful to clarify the situation patients are closely monitored over at least 12 hours for
where there is any doubt. clinical signs of postbiopsy hemorrhage. Evaluation of
heart rate, mucous membrane color, abdominal size, and
Prebiopsy Considerations mentation is important. Measurement of total protein
When planning liver biopsy, there are several important and packed cell volume does not provide useful informa-
factors to consider, including risk to the patient and the tion when monitoring for acute hemorrhage.
type of biopsy procedure to be used. The main types of
biopsy approaches available are ultrasound‐guided nee- Ultrasound‐Guided Biopsy
dle biopsy, laparoscopic biopsy, and surgical biopsy. The Ultrasound‐guided biopsies involve the use of a cutting‐
most important potential complications of liver biopsy type needle which is ideally automated or semiauto-
are hemorrhage, trauma to adjacent organs, and infec- mated. These are spring‐loaded needles similar to the
tion, the relative risks of which vary with the technique manual Tru‐cut style and help when coordinating opera-
used and are discussed further later. tion of the ultrasound probe with one hand and the
It is important to evaluate the overall clinical stability biopsy gun with the other. The fully automated devices
of a patient and hemostatic function prior to obtaining a initially fire the inner part of the needle containing the
liver biopsy. The circulatory status and potential for biopsy channel and then the outer cutting device rapidly
hemorrhage should be considered in addition to how afterwards. The semiautomated ones allow the operator