Clinical Biochemistry of Domestic Animals (Sixth Edition) - UMK ...

Chapter 13
Hepatic Function
Bud C. Tennant
Department of Clinical Sciences
New York State College of Veterinary Medicine
Cornell University
Ithaca, New York
Sharon A. Center
Department of Clinical Sciences
New York State College of Veterinary Medicine
Cornell University
Ithaca, New York
I. INTRODUCTION
II. FUNCTIONAL ANATOMY
III. CLINICAL MANIFESTATIONS OF HEPATIC
INSUFFICIENCY
A. Icterus
B. Hepatic Encephalopathy
C. Hepatic Photosensitivity
D. Ascites
IV. LABORATORY ASSESSMENT OF HEPATIC
FUNCTION
A. Hepatic Enzymes
B. Serum Bilirubin
C. Serum Bile Acids
D. Serum Proteins
E. Dye Excretion
V. OVERVIEW AND CONCLUSIONS
REFERENCES
advances have been made in our understanding of the
pathophysiological, biochemical, and molecular mechanisms
responsible for hepatic disease. Our current knowledge
of veterinary hepatology is the result of the collective
work of individuals from a variety of disciplines, including
practicing veterinarians, biomedical scientists, and,
more recently, molecular and cell biologists and molecular
geneticists. No one individual had a more important or
sustained impact than Dr. Cornelius, and no one was more
active in maintaining a comparative perspective on the subject
( Cornelius, 1993 ). In this chapter, we describe the biochemical
mechanisms responsible for the cardinal clinical
manifestations of hepatic insufficiency and the biochemical
tests used in the clinical diagnosis of liver disease and
to assess hepatic function. As in previous editions, the goal
is to provide students of veterinary medicine at all stages
of career development with information useful for managing
the diseases of animal patients.
I . INTRODUCTION
The liver has an essential role in nutrient metabolism
including the control and maintenance of the blood glucose
level; in detoxification and excretion of hydrophobic
metabolites and xenobiotics; in the synthesis of most
plasma proteins; and in digestion through synthesis, biliary
secretion, and conservation of bile acids that are essential
both for digestion and intestinal absorption of fats and
other lipids including fat soluble vitamins. The clinical
manifestations of hepatic disease are directly attributable
to alterations in the metabolic, excretory, synthetic, and
digestive functions of the liver. The liver has great reserve,
and signs of hepatic failure often do not develop until 70%
or more of functional capacity is lost. Importantly, even
when a major fraction of the hepatocellular mass has been
lost following acute injury, recovery is possible because of
the unique regenerative capacity of the liver.
Since Dr. Charles E. Cornelius wrote this chapter for earlier
editions of this textbook (Cornelius, 1970), remarkable
II . FUNCTIONAL ANATOMY
During embryological development, the liver arises as an
outgrowth of the primitive gut and is located cranial to the
abdominal viscera and other abdominal organs between
the splanchnic and the peripheral (systemic) circulatory
systems. Unlike other mammalian organs, afferent blood to
the liver is derived from two sources, the hepatic artery and
the hepatic portal vein. Efferent blood leaves the liver by
the hepatic vein and enters the systemic circulation via the
caudal vena cava. Twenty to 30% of afferent blood comes
from the hepatic artery, and the remainder from the hepatic
portal vein, which drains the pancreas, spleen, stomach,
small intestine, and all but the most terminal portion of the
large intestine.
The peripheral border of the classical liver lobule is
formed by the most peripheral row of hepatocytes (the
terminal plate) and by two, three, or more portal tracks
(portal triads) that contain preterminal branches of the
hepatic artery, the hepatic portal vein, and bile ductules.
Clinical Biochemistry of Domestic Animals, 6th Edition 379
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