C h a p t e r 3 0
Disorders of Hepatobiliary and Exocrine Pancreas Function
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Unrelieved obstruction leads to biliary tract fibrosis and
ultimately to end-stage biliary cirrhosis.
Pruritus is the most common presenting symptom
in persons with cholestasis, probably related to an
elevation in plasma bile acids. Skin xanthomas (focal
accumulations of cholesterol) may occur as the result
of hyperlipidemia and impaired excretion of choles-
terol. A characteristic laboratory finding is elevated
levels of serum ALP. Other manifestations of reduced
bile flow relate to intestinal absorption, including
nutritional deficiencies of the fat-soluble vitamins A,
D, E, and K.
Tests of Hepatobiliary Function
The history and physical examination, in most instances,
provide clues about liver function. Diagnostic tests help
to evaluate liver function and the extent of liver damage.
Laboratory tests commonly are used to assess liver func-
tion and confirm the diagnosis of liver disease.
Liver function tests, including serum levels of liver
enzymes, are used to assess injury to liver cells, the liver’s
ability to synthesize proteins, and the excretory functions
of the liver.
5,6
Elevated serum enzyme test results usually
indicate liver injury earlier than other indicators of liver
function. The key enzymes are alanine aminotransferase
(ALT) and aspartate aminotransferase (AST), which are
present in liver cells. ALT is liver specific, whereas AST
is derived from organs other than the liver. In most cases
of liver damage, there are parallel rises in ALT and AST.
The most dramatic rise is seen in cases of acute hepa-
tocellular injury, as occurs with viral hepatitis, autoim-
mune hepatitis, hypoxic or ischemic injury, acute toxic
injury, or Reye syndrome. The liver’s synthetic capacity
is reflected in measures of serum protein levels (albumin)
and prothrombin time (i.e., synthesis of coagulation fac-
tors). Deficiencies of fibrinogen and coagulation factors
(II, VII, IX, and X) may occur.
Serum bilirubin,
γ
-glutamyltransferase (GGT), and
ALP measure hepatic excretory function.
6
Alkaline phos-
phatase is present in the membranes between liver cells
and the bile duct and is released by disorders affecting
the bile duct.
γ
-glutamyltransferase, which is thought to
function in the transport of amino acids and peptides
into liver cells, is a sensitive indicator of hepatobiliary
disease but not used much clinically as it has limited use
in specific disease diagnosis.
Ultrasonography provides information about the
size, composition, and blood flow of the liver. It is used
predominately in detecting stones in the gallbladder or
biliary tree. Computed tomography (CT) scanning and
magnetic resonance imaging (MRI) provide informa-
tion similar to that obtained by ultrasonography, but
offer greater detail regarding composition, and blood
and/or bile flow through the liver. Selective angiog-
raphy of the celiac, superior mesenteric, or hepatic
artery may be used to visualize the hepatic or portal
circulation.
A liver biopsy affords a means of examining liver
tissue without surgery. There are several methods for
obtaining liver tissue: percutaneous liver biopsy, which
uses a suction, cutting, or spring-loaded cutting needle;
laparoscopic liver biopsy; and fine needle biopsy, which
is performed under ultrasonographic or CT guidance.
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The type of method used is based on the number of
specimens needed and the amount of tissue required
for evaluation. Laparoscopic liver biopsy provides the
means for examining abdominal masses and staging
liver cancers.
Disorders of Hepatic and Biliary
Function
The structures of the hepatobiliary system are subject to
many of the same pathologic conditions that affect other
body systems. This section focuses on alterations in liver
function due to viral and autoimmune hepatitis; intrahe-
patic biliary disorders; drug- and alcohol-induced liver
disease; nonalcoholic fatty liver disease; the hepatic syn-
dromes of cirrhosis, portal hypertension, and liver fail-
ure; and cancer of the liver.
SUMMARY CONCEPTS
■■
The liver, which is the largest and most
versatile organ in the body, is located between
the gastrointestinal tract and the systemic
circulation. Venous blood from the intestine
flows through the liver before it is returned to
the heart, allowing nutrients to be removed for
processing and storage, and bacteria and other
foreign matter to be removed before the blood is
returned to the systemic circulation.
■■
The main functions of the liver include synthesis
of plasma proteins, maintenance of blood glucose
levels, regulation of circulating lipoprotein
levels, and vitamin and mineral storage.The liver
also plays an essential role in the metabolism
and elimination of harmful toxins and drugs,
conversion of ammonia to urea, and removal of
bilirubin, a product of hemoglobin breakdown,
from the blood.
■■
Serum liver enzymes, especially alanine
aminotransferase (ALT) and aspartate
aminotransferase (AST), are used to assess
injury to liver cells; plasma proteins (e.g., serum
albumin) and blood clotting factors (prothrombin
time) provide information related to the liver’s
synthetic capacity; and serum bilirubin, serum
γ
-glutamyltransferase (GGT), and alkaline
phosphatase (ALP) are used as measures of
hepatic excretory function.
