C h a p t e r 3 0
Disorders of Hepatobiliary and Exocrine Pancreas Function
745
SUMMARY CONCEPTS
■■
The liver is subject to most of the disease
processes that affect other body structures, such
as infections, autoimmune disorders, toxic injury,
metabolic diseases, and neoplasms.
■■
Hepatitis is characterized by inflammation of the
liver. Viral hepatitis is caused by hepatitis viruses
A, B, C, D, and E, which differ in terms of mode
of transmission, incubation period, mechanism,
degree and chronicity of liver damage, and ability
to evolve to a carrier state. Autoimmune hepatitis
involves the immune destruction of hepatocytes
causing inflammation.
■■
Intrahepatic biliary diseases disrupt the flow of bile
through the liver, causing cholestasis and biliary
cirrhosis. Causes of intrahepatic biliary diseases
include primary biliary cirrhosis, primary sclerosing
cholangitis, and secondary biliary cirrhosis.
■■
The liver, which is the major drug-metabolizing
and detoxifying organ in the body, is subject to
potential damage from an enormous array of
pharmaceutical and environmental chemicals.
There are two types of drug reactions: predictable,
based on the drug’s chemical structure and
metabolites, and idiosyncratic, based on individual
characteristics of the person receiving the drug.
■■
Cirrhosis represents the end stage of chronic liver
disease in which much of the liver’s functional
tissue has been replaced by fibrous tissue that
disrupts venous blood flow predisposing to portal
hypertension and its complications, loss of liver
cells, and eventual liver failure.
■■
Portal hypertension is characterized by increased
resistance to flow and increased pressure
in the portal venous system, the pathologic
consequences of which include ascites, the
formation of collateral bypass channels (e.g.,
esophageal varices), and splenomegaly.
■■
The manifestations of liver failure reflect
the various functions of the liver, including
hematologic disorders, disruption of endocrine
function, skin disorders, hepatorenal syndrome,
and hepatic encephalopathy.
■■
There are two types of primary cancers of the liver.
Hepatocellular cancer, the most common form,
is derived from hepatocytes and their precursors
and is associated with conditions such as chronic
hepatitis B and C infection and alcoholic cirrhosis.
Cholangiocarcinoma, or bile duct cancer, arises
from the biliary epithelium, typically following
long-standing inflammation of the bile ducts.
Disorders of the Hepatobiliary
System and Exocrine Pancreas
The hepatobiliary system consists of the gallbladder;
the left and right hepatic ducts, which come together
to form the common hepatic duct; the cystic duct,
which extends to the gallbladder; and the bile duct,
which is formed by the union of the common hepatic
duct and the cystic duct
2
(Fig. 30-15). The bile duct
descends posteriorly to the first part of the duodenum,
where it comes in contact with the main pancreatic
duct. These ducts unite to form the hepatopancreatic
ampulla. The circular muscle around the distal end of
the bile duct is thickened to form the sphincter of the
bile duct.
The pancreas lies transversely in the posterior part
of the upper abdomen (see Fig. 30-1). The head of the
pancreas is at the right of the abdomen; it rests against
the curve of the duodenum in the area of the hepato-
pancreatic ampulla and its entrance into the duodenum.
The body of the pancreas lies beneath the stomach,
with the tail touching the spleen. The pancreas is vir-
tually hidden because of its posterior position; unlike
many other organs, it cannot be palpated. Because of
the position of the pancreas and its large functional
reserve, symptoms from conditions such as cancer of
the pancreas do not usually appear until the disorder
is far advanced.
Disorders of the Hepatobiliary
System
The gallbladder is a distensible, pear-shaped muscular
sac located on the ventral surface of the liver.
2
It has an
outer serous peritoneal layer, a middle smooth muscle
layer, and an inner mucosal layer that is continuous
with the lining of the bile duct. The function of the gall-
bladder is to store and concentrate bile. In the gallblad-
der, water and electrolytes are absorbed from the bile,
causing the concentration of bile salts and lecithin to
increase, along with that of cholesterol; in this way, the
solubility of cholesterol is maintained.
Entrance of food into the intestine causes the gall-
bladder to contract and the sphincter of the bile duct to
relax, such that bile stored in the gallbladder moves into
the duodenum. The stimulus for gallbladder contrac-
tion is primarily hormonal. Products of food digestion,
particularly lipids, stimulate the release of a gastrointes-
tinal hormone called
cholecystokinin
from the mucosa
of the duodenum. Cholecystokinin provides a strong
stimulus for gallbladder contraction. The role of other
gastrointestinal hormones in bile release is less clearly
understood.
Passage of bile into the intestine is regulated largely
by the pressure in the common bile duct. Normally, the
gallbladder regulates this pressure. It collects and stores
bile as it relaxes and the pressure in the common bile
duct decreases, and it empties bile into the intestine
as the gallbladder contracts, producing an increase in
common duct pressure. After gallbladder surgery, the
